7.1. Tutorial (Todo Application REST)

7.1.1. Introduction

7.1.1.1. Points to study in this tutorial

  • Basic RESTful web service development using TERASOLUNA Server Framework for Java (5.x)

7.1.1.2. Target readers

7.1.1.3. Verification environment

In this tutorial, operations are verified on following environment.
In order to use the advanced features of Google Chrome, Google Chrome used as a Web Browser for REST Client.
Type Product
REST Client DHC(aka Dev HTTP Client) 0.7.11
Product other than the above Similar to Tutorial (Todo Application)

7.1.2. Environment creation

Assumes that Java, STS, Maven, Google Chrome are already installed since the Tutorial (Todo Application) is implemented.

7.1.2.1. Install DHC

As a REST client, install [DHC] advanced features of Google Chrome.

Select [Tools] -> [Extensions] of Chrome browser.

../_images/install-dev-http-client1.png

Click [Get more extensions] link.

../_images/install-dev-http-client2.png

Search by entering [dev http client] in search form.

../_images/install-dev-http-client3.png

Click the [+ FREE] button of Dev HTTP Client.

../_images/install-dev-http-client4.png

Click [Add] button.

../_images/install-dev-http-client5.png

When you open the application list (Open by specifying [chrome://apps/] in your browser address bar) of Chrome, DHC has been added.

../_images/install-dev-http-client6.png

Click the DHC.
If the following screen appears, the installation is completed.
This screen can also be opened by entering the [chrome-extension://aejoelaoggembcahagimdiliamlcdmfm/dhc.html] in the address bar of the browser.
../_images/install-dev-http-client7.png

7.1.2.2. Project creation

In this tutorial, the RESTful Web Services are created for [Tutorial (Todo Application)].

Therefore, if [Tutorial (Todo Application)] project is not exists, re-create project by executing [Tutorial (Todo Application)].

Note

If project is re-created by executing [Tutorial (Todo Application)], it is possible to proceed further this tutorial by performing re-creation till the domain layer creation.


7.1.3. REST API creation

In this tutorial, creating REST API for publishing the data on Web which are managed in the todo table (here onwards called as [Todo Resources]).

API name
HTTP
method
Path
Status
code
Description
GET Todos
GET
/api/v1/todos
200
(OK)
Fetch all records of Todo Resource.
POST Todos
POST
/api/v1/todos
201
(Created)
Create new Todo Resource.
GET Todo
GET
/api/v1/todos/{todoId}
200
(OK)
Fetch one record of Todo Resource.
PUT Todo
PUT
/api/v1/todos/{todoId}
200
(OK)
Update Todo Resource in completed status
DELETE Todo
DELETE
/api/v1/todos/{todoId}
204
(No Content)
Delete Todo Resource.

Tip

The {todoId} included in path is called as path variable and can deal with any changeable value. The GET /api/v1/todos/123 and GET /api/v1/todos/456 can be handle with same API using the path variable.

In this tutorial, We are dealing with ID (Todo ID) as the path variable in order to uniquely identifying the Todo.


7.1.3.1. API specification

Indicated the REST API Interface specifications using specific example of the HTTP requests and responses in this tutorial.
HTTP headers which are not essential have been excluded from the example.

7.1.3.1.1. GET Todos

[Request]

> GET /todo/api/v1/todos HTTP/1.1

[Response]

Return list of created Todo Resource in JSON format.

< HTTP/1.1 200 OK
< Content-Type: application/json;charset=UTF-8
<
[{"todoId":"9aef3ee3-30d4-4a7c-be4a-bc184ca1d558","todoTitle":"Hello World!","finished":false,"createdAt":"2014-02-25T02:21:48.493+0000"}]

7.1.3.1.2. POST Todos

[Request]

Specify newly creation Todo Resource content (Title) in JSON format.

> POST /todo/api/v1/todos HTTP/1.1
> Content-Type: application/json
> Content-Length: 29
>
{"todoTitle": "Study Spring"}

[Response]

Return created Todo Resource in JSON format.

< HTTP/1.1 201 Created
< Content-Type: application/json;charset=UTF-8
<
{"todoId":"d6101d61-b22c-48ee-9110-e106af6a1404","todoTitle":"Study Spring","finished":false,"createdAt":"2014-02-25T04:05:58.752+0000"}

7.1.3.1.3. GET Todo

[Request]

Specify ID of the Todo Resource in [todoId] path variable that you want to fetch.
In below example, 9aef3ee3-30d4-4a7c-be4a-bc184ca1d558 is specified in [todoId] path variable.
> GET /todo/api/v1/todos/9aef3ee3-30d4-4a7c-be4a-bc184ca1d558 HTTP/1.1

[Response]

Return Todo Resource in JSON format that matches with the [todoId] path variable.

< HTTP/1.1 200 OK
< Content-Type: application/json;charset=UTF-8
<
{"todoId":"9aef3ee3-30d4-4a7c-be4a-bc184ca1d558","todoTitle":"Hello World!","finished":false,"createdAt":"2014-02-25T02:21:48.493+0000"}

7.1.3.1.4. PUT Todo

[Request]

Specify ID of the Todo Resource in [todoId] path variable that you want to update.
In the PUT Todo, interface specification does not receive the request BODY because Todo Resource is only updating into completion state.
> PUT /todo/api/v1/todos/9aef3ee3-30d4-4a7c-be4a-bc184ca1d558 HTTP/1.1

[Response]

Return Todo Resource in JSON format that matches with the [todoId] path variable after updating in completed status (true of finished field).

< HTTP/1.1 200 OK
< Content-Type: application/json;charset=UTF-8
<
{"todoId":"9aef3ee3-30d4-4a7c-be4a-bc184ca1d558","todoTitle":"Hello World!","finished":true,"createdAt":"2014-02-25T02:21:48.493+0000"}

7.1.3.1.5. DELETE Todo

[Request]

Specify ID of the Todo Resource in [todoId] path variable that you want to delete.

> DELETE /todo/api/v1/todos/9aef3ee3-30d4-4a7c-be4a-bc184ca1d558 HTTP/1.1

[Response]

In the DELETE Todo, since the Todo Resource is deleted and resource that can return is no longer exists, interface specification does not return the response BODY.

< HTTP/1.1 204 No Content

7.1.3.1.6. Error Response

Return error in JSON format in case of any error occurs in REST API.
The response specification of typical errors are described below.
Error patterns other than the below are also exists but description in the tutorial are omitted.

In the Tutorial (Todo Application), error messages are hardcoded in the program but in this tutorial, it is modified such a way that the error messages are retrieved from the property file based on error code.

[Response specification at the time of input check error]

< HTTP/1.1 400 Bad Request
< Content-Type: application/json;charset=UTF-8
<
{"code":"E400","message":"[E400] The requested Todo contains invalid values.","details":[{"code":"NotNull","message":"todoTitle may not be null.",target:"todoTitle"}]}

[Response specification at the time of business error]

< HTTP/1.1 409 Conflict
< Content-Type: application/json;charset=UTF-8
<
{"code":"E002","message":"[E002] The requested Todo is already finished. (id=353fb5db-151a-4696-9b4a-b958358a5ab3)"}

[Response specification at the time of resources undetected]

< HTTP/1.1 404 Not Found
< Content-Type: application/json;charset=UTF-8
<
{"code":"E404","message":"[E404] The requested Todo is not found. (id=353fb5db-151a-4696-9b4a-b958358a5ab2)"}

[Response specification at the time of system error]

< HTTP/1.1 500 Internal Server Error
< Content-Type: application/json;charset=UTF-8
<
{"code":"E500","message":"[E500] System error occurred."}

7.1.3.2. DispatcherServlet for REST API

First, add the definition of DispatcherServlet for processing the REST API request.

7.1.3.2.1. Modification of web.xml

Add configuration pertaining to REST API.
src/main/webapp/WEB-INF/web.xml
<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="http://java.sun.com/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd"
    version="3.0">
    <listener>
        <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
    </listener>
    <listener>
        <listener-class>org.terasoluna.gfw.web.logging.HttpSessionEventLoggingListener</listener-class>
    </listener>
    <context-param>
        <param-name>contextConfigLocation</param-name>
        <!-- Root ApplicationContext -->
        <param-value>
            classpath*:META-INF/spring/applicationContext.xml
            classpath*:META-INF/spring/spring-security.xml
        </param-value>
    </context-param>

    <filter>
        <filter-name>MDCClearFilter</filter-name>
        <filter-class>org.terasoluna.gfw.web.logging.mdc.MDCClearFilter</filter-class>
    </filter>
    <filter-mapping>
        <filter-name>MDCClearFilter</filter-name>
        <url-pattern>/*</url-pattern>
    </filter-mapping>

    <filter>
        <filter-name>exceptionLoggingFilter</filter-name>
        <filter-class>org.springframework.web.filter.DelegatingFilterProxy</filter-class>
    </filter>
    <filter-mapping>
        <filter-name>exceptionLoggingFilter</filter-name>
        <url-pattern>/*</url-pattern>
    </filter-mapping>

    <filter>
        <filter-name>XTrackMDCPutFilter</filter-name>
        <filter-class>org.terasoluna.gfw.web.logging.mdc.XTrackMDCPutFilter</filter-class>
    </filter>
    <filter-mapping>
        <filter-name>XTrackMDCPutFilter</filter-name>
        <url-pattern>/*</url-pattern>
    </filter-mapping>

    <filter>
        <filter-name>CharacterEncodingFilter</filter-name>
        <filter-class>org.springframework.web.filter.CharacterEncodingFilter</filter-class>
        <init-param>
            <param-name>encoding</param-name>
            <param-value>UTF-8</param-value>
        </init-param>
        <init-param>
            <param-name>forceEncoding</param-name>
            <param-value>true</param-value>
        </init-param>
    </filter>
    <filter-mapping>
        <filter-name>CharacterEncodingFilter</filter-name>
        <url-pattern>/*</url-pattern>
    </filter-mapping>

    <filter>
        <filter-name>springSecurityFilterChain</filter-name>
        <filter-class>org.springframework.web.filter.DelegatingFilterProxy</filter-class>
    </filter>

    <filter-mapping>
        <filter-name>springSecurityFilterChain</filter-name>
        <url-pattern>/*</url-pattern>
    </filter-mapping>

    <!-- (1) -->
    <servlet>
        <servlet-name>restApiServlet</servlet-name>
        <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
        <init-param>
            <param-name>contextConfigLocation</param-name>
            <!-- ApplicationContext for Spring MVC (REST) -->
            <param-value>classpath*:META-INF/spring/spring-mvc-rest.xml</param-value>
        </init-param>
        <load-on-startup>1</load-on-startup>
    </servlet>

    <!-- (2) -->
    <servlet-mapping>
        <servlet-name>restApiServlet</servlet-name>
        <url-pattern>/api/v1/*</url-pattern>
    </servlet-mapping>

    <servlet>
        <servlet-name>appServlet</servlet-name>
        <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
        <init-param>
            <param-name>contextConfigLocation</param-name>
            <!-- ApplicationContext for Spring MVC -->
            <param-value>classpath*:META-INF/spring/spring-mvc.xml</param-value>
        </init-param>
        <load-on-startup>1</load-on-startup>
    </servlet>

    <servlet-mapping>
        <servlet-name>appServlet</servlet-name>
        <url-pattern>/</url-pattern>
    </servlet-mapping>

    <jsp-config>
        <jsp-property-group>
            <url-pattern>*.jsp</url-pattern>
            <el-ignored>false</el-ignored>
            <page-encoding>UTF-8</page-encoding>
            <scripting-invalid>false</scripting-invalid>
            <include-prelude>/WEB-INF/views/common/include.jsp</include-prelude>
        </jsp-property-group>
    </jsp-config>

    <error-page>
        <error-code>500</error-code>
        <location>/WEB-INF/views/common/error/systemError.jsp</location>
    </error-page>
    <error-page>
        <error-code>404</error-code>
        <location>/WEB-INF/views/common/error/resourceNotFoundError.jsp</location>
    </error-page>
    <error-page>
        <exception-type>java.lang.Exception</exception-type>
        <location>/WEB-INF/views/common/error/unhandledSystemError.html</location>
    </error-page>

    <session-config>
        <!-- 30min -->
        <session-timeout>30</session-timeout>
    </session-config>

</web-app>
Sr. No Description
(1)
Specify the SpringMVC configuration file for REST at the initialization parameter [contextConfigLocation].
In this tutorial, [META-INF/spring/spring-mvc-rest.xml] is specified located at class path.
(2)
Specify the URL pattern that maps to the DispatcherServlet for REST API at <url-pattern> element.
In this tutorial, if it starts from /api/v1/, request is considered as a REST API request and mapped with the DispatcherServlet for REST API.

7.1.3.2.2. Creation of spring-mvc-rest.xml

Spring MVC configuration file for REST is created by copying the src/main/resources/META-INF/spring/spring-mvc.xmlfile.
The definition of SpringMVC configuration for REST file will be as follows.
../_images/add-spring-mvc-rest.png

src/main/resources/META-INF/spring/spring-mvc-rest.xml

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:context="http://www.springframework.org/schema/context"
    xmlns:mvc="http://www.springframework.org/schema/mvc" xmlns:util="http://www.springframework.org/schema/util"
    xmlns:aop="http://www.springframework.org/schema/aop"
    xsi:schemaLocation="http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc.xsd
        http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
        http://www.springframework.org/schema/util http://www.springframework.org/schema/util/spring-util.xsd
        http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsd
        http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop.xsd">

    <context:property-placeholder
        location="classpath*:/META-INF/spring/*.properties" />

    <mvc:annotation-driven>
        <mvc:argument-resolvers>
            <bean
                class="org.springframework.data.web.PageableHandlerMethodArgumentResolver" />
            <bean
                class="org.springframework.security.web.bind.support.AuthenticationPrincipalArgumentResolver" />
        </mvc:argument-resolvers>
        <mvc:message-converters register-defaults="false">
            <!-- (1) -->
            <bean
                class="org.springframework.http.converter.json.MappingJackson2HttpMessageConverter">
                <!-- (2) -->
                <property name="objectMapper">
                    <bean class="com.fasterxml.jackson.databind.ObjectMapper">
                        <property name="dateFormat">
                            <!-- (3) -->
                            <bean class="com.fasterxml.jackson.databind.util.StdDateFormat"/>
                        </property>
                    </bean>
                </property>
            </bean>
        </mvc:message-converters>
    </mvc:annotation-driven>

    <mvc:default-servlet-handler />

    <context:component-scan base-package="todo.api" /> <!-- (3) -->

    <mvc:interceptors>
        <mvc:interceptor>
            <mvc:mapping path="/**" />
            <mvc:exclude-mapping path="/resources/**" />
            <mvc:exclude-mapping path="/**/*.html" />
            <bean
                class="org.terasoluna.gfw.web.logging.TraceLoggingInterceptor" />
        </mvc:interceptor>
        <!--  REMOVE THIS LINE IF YOU USE JPA
        <mvc:interceptor>
            <mvc:mapping path="/**" />
            <mvc:exclude-mapping path="/resources/**" />
            <mvc:exclude-mapping path="/**/*.html" />
            <bean
                class="org.springframework.orm.jpa.support.OpenEntityManagerInViewInterceptor" />
        </mvc:interceptor>
            REMOVE THIS LINE IF YOU USE JPA  -->
    </mvc:interceptors>

    <!-- Setting AOP. -->
    <bean id="handlerExceptionResolverLoggingInterceptor"
        class="org.terasoluna.gfw.web.exception.HandlerExceptionResolverLoggingInterceptor">
        <property name="exceptionLogger" ref="exceptionLogger" />
    </bean>
    <aop:config>
        <aop:advisor advice-ref="handlerExceptionResolverLoggingInterceptor"
            pointcut="execution(* org.springframework.web.servlet.HandlerExceptionResolver.resolveException(..))" />
    </aop:config>

</beans>
Sr. No Description
(1)

Set the class(org.springframework.http.converter.HttpMessageConverter) to serialize/de-serialize the JavaBean dealing with arguments and return values of the Controller at <mvc:message-converters>.

Multiple HttpMessageConverter can be configured but, since only JSON is used in this tutorial only MappingJackson2HttpMessageConverter is specified.

(2)

Specify the ObjectMapper(Component for conversion of [JSON <-> JavaBean]) that is provided by Jackson into the objectMapper property of the MappingJackson2HttpMessageConverter.

In this tutorial, Data format customized ObjectMapper is specified. objectMapperproperty can be omitted if customization is not required.

(3)

Specify format of the Date field into dateFormat property of ObjectMapper.

In this tutorial, ISO-8601 format used while serializing java.util.Date object. If you want to use ISO-8601 format while serializing Date object, it can be implemented by configuring the com.fasterxml.jackson.databind.util.StdDateFormat.

(4)

Scan the components under the package of the REST API

In this tutorial, the package of REST API is todo.api. Although the Controllers for the screen transition had been stored under app package, Controllers for REST API are recommended to store under api package.


7.1.3.3. Definition of Spring Security for REST API

Disabled the CSRF protection in REST API created in this tutorial.
CSRF protection is required even in Web application of the REST API. However, the purpose of this tutorial is not CSRF measures hence ignored the explanation.
If you disable the CSRF protection, the use of session is not required.
Therefore, in this tutorial, adopted an architecture that does not use the session(stateless architecture) and disable the CSRF measures.
The use of session and CSRF measures can be avoided by adding the following settings.
src/main/resources/META-INF/spring/spring-security.xml
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:sec="http://www.springframework.org/schema/security"
    xmlns:context="http://www.springframework.org/schema/context"
    xsi:schemaLocation="http://www.springframework.org/schema/security http://www.springframework.org/schema/security/spring-security.xsd
        http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
        http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsd">

    <sec:http pattern="/resources/**" security="none"/>

    <!-- (1) -->
    <sec:http
        pattern="/api/v1/**"
        auto-config="true"
        use-expressions="true"
        create-session="stateless">
        <sec:headers />
    </sec:http>

    <sec:http auto-config="true" use-expressions="true">
        <sec:headers>
            <sec:cache-control />
            <sec:content-type-options />
            <sec:hsts />
            <sec:frame-options />
            <sec:xss-protection />
        </sec:headers>
        <sec:csrf />
        <sec:access-denied-handler ref="accessDeniedHandler"/>
        <sec:custom-filter ref="userIdMDCPutFilter" after="ANONYMOUS_FILTER"/>
        <sec:session-management />
    </sec:http>

    <sec:authentication-manager></sec:authentication-manager>

    <!-- Change View for CSRF or AccessDenied -->
    <bean id="accessDeniedHandler"
        class="org.springframework.security.web.access.DelegatingAccessDeniedHandler">
        <constructor-arg index="0">
            <map>
                <entry
                    key="org.springframework.security.web.csrf.InvalidCsrfTokenException">
                    <bean
                        class="org.springframework.security.web.access.AccessDeniedHandlerImpl">
                        <property name="errorPage"
                            value="/WEB-INF/views/common/error/invalidCsrfTokenError.jsp" />
                    </bean>
                </entry>
                <entry
                    key="org.springframework.security.web.csrf.MissingCsrfTokenException">
                    <bean
                        class="org.springframework.security.web.access.AccessDeniedHandlerImpl">
                        <property name="errorPage"
                            value="/WEB-INF/views/common/error/missingCsrfTokenError.jsp" />
                    </bean>
                </entry>
            </map>
        </constructor-arg>
        <constructor-arg index="1">
            <bean
                class="org.springframework.security.web.access.AccessDeniedHandlerImpl">
                <property name="errorPage"
                    value="/WEB-INF/views/common/error/accessDeniedError.jsp" />
            </bean>
        </constructor-arg>
    </bean>

    <!-- Put UserID into MDC -->
    <bean id="userIdMDCPutFilter" class="org.terasoluna.gfw.security.web.logging.UserIdMDCPutFilter">
    </bean>

</beans>
Sr. No Description
(1)
Add the definition of Spring Security for REST API.
Specify the URL pattern of the REST API request path at pattern attribute of the <sec:http> element.
In this tutorial, request path starts with /api/v1/ is considered as a REST API request.
Furthermore, session is no longer used in the processing of Spring Security by specifying stateless at create-session attribute.

7.1.3.4. Creation of REST API package

Create a package that stores the REST API classes.

The name of the root package is api that contains the REST API classes and recommended to create a package of each resource (lowercase resource name) under it.
Since the name of the resource is Todo in this tutorial, the todo.api.todo package is created.
../_images/make-package-for-rest.png

Note

Usually following three types of classes are stored in the created package. The following naming rules are recommended for the classes.

  • [Resource name]Resource
  • [Resource name]RestController
  • [Resource name]Helper (if required)

Since name of the resource is Todo in this tutorial,

  • TodoResource
  • TodoRestController

is created

The TodoRestHelper is not created in this tutorial.


7.1.3.5. Creation of Resource class

Create TodoResource class for implementing Todo Resource.
In this guide line, Java Bean that represent the JSON(or XML) for input and output of the REST API is called as Resource class.

src/main/java/todo/api/todo/TodoResource.java

package todo.api.todo;

import java.io.Serializable;
import java.util.Date;

import javax.validation.constraints.NotNull;
import javax.validation.constraints.Size;

public class TodoResource implements Serializable {

    private static final long serialVersionUID = 1L;

    private String todoId;

    @NotNull
    @Size(min = 1, max = 30)
    private String todoTitle;

    private boolean finished;

    private Date createdAt;

    public String getTodoId() {
        return todoId;
    }

    public void setTodoId(String todoId) {
        this.todoId = todoId;
    }

    public String getTodoTitle() {
        return todoTitle;
    }

    public void setTodoTitle(String todoTitle) {
        this.todoTitle = todoTitle;
    }

    public boolean isFinished() {
        return finished;
    }

    public void setFinished(boolean finished) {
        this.finished = finished;
    }

    public Date getCreatedAt() {
        return createdAt;
    }

    public void setCreatedAt(Date createdAt) {
        this.createdAt = createdAt;
    }
}

Note

The reason for creating a Resource class in spite of the existence of the DomainObject class (Todo class in this tutorial), business process is not consistent with the interface to be used in the input and output of the client.

If it is used wrongly, application layer will be impacted to the domain layer and also decrease the maintainability. It is recommended to perform the data conversion using BeanMapper such as Dozer by creating DomainObject and Resource class separately.

The role of the Resource class is similar to the Form class but eventually it is differing like Form class represent the <form> tag of HTML in JavaBean and Resource class is the input and output of the REST API in JavaBean.

However, it is a JavaBean having annotation of the Bean Validation and the Controller class is approximately the same as the Form class because stored in the same package.


7.1.3.6. Creation of Controller class

Create a TodoRestController class that provides a REST API of TodoResource.

src/main/java/todo/api/todo/TodoRestController.java

package todo.api.todo;

import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

@RestController // (1)
@RequestMapping("todos") // (2)
public class TodoRestController {

}
Sr. No Description
(1)
Specify the @RestController annotation.
Refer to the Creation of RestController class for the details of @RestController.
(2)
Specify the resource path.
Since /api/v1/ is defined in web.xml, it is mapped with the /<contextPath>/api/v1/todos path by perform this setting.

7.1.3.6.1. Implementation of GET Todos

Implement the processing of API(GET Todos) into getTodos method of TodoRestController that fetches all records of created Todo Resource.

src/main/java/todo/api/todo/TodoRestController.java

package todo.api.todo;

import java.util.ArrayList;
import java.util.Collection;
import java.util.List;

import javax.inject.Inject;

import org.dozer.Mapper;
import org.springframework.http.HttpStatus;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.ResponseStatus;
import org.springframework.web.bind.annotation.RestController;

import todo.domain.model.Todo;
import todo.domain.service.todo.TodoService;

@RestController
@RequestMapping("todos")
public class TodoRestController {

    @Inject
    TodoService todoService;
    @Inject
    Mapper beanMapper;

    @RequestMapping(method = RequestMethod.GET) // (1)
    @ResponseStatus(HttpStatus.OK) // (2)
    public List<TodoResource> getTodos() {
        Collection<Todo> todos = todoService.findAll();
        List<TodoResource> todoResources = new ArrayList<>();
        for (Todo todo : todos) {
            todoResources.add(beanMapper.map(todo, TodoResource.class)); // (3)
        }
        return todoResources; // (4)
    }

}
Sr. No Description
(1)
Set the RequestMethod.GET to method attribute for handling the GET request.
(2)
Specify @ResponseStatus annotation to the HTTP status code for response.
To set “200 OK” as a HTTP status, set the HttpStatus.OK to the value attribute.
(3)
Converting Todo object returned from findAll method of TodoService into TodoResource object type that represent JSON response.
It is convenient to use the org.dozer.Mapper interface of Dozer for converting Todo and TodoResource.
(4)
By returning the List<TodoResource> object, it is serialized into JSON by MappingJackson2HttpMessageConverter defined in spring-mvc-rest.xml.

Check the operation of the implemented API by booting Application Server.

Access the REST API(Get Todos).
Open the DHC, enter "localhost:8080/todo/api/v1/todos" in the URL, specify GET in method and click the “Send” button.
../_images/get-todos1.png

Displays JSON execution results in [BODY] of the [RESPONSE] as follows.
Since data is not registered at present, an empty array [] is returned.
../_images/get-todos2.png

Since the Spring Security setting has been changed to not use the session therefore want to focus on the point that "Set-Cookie: JSESSIONID=xxxx" is not exists in the [RESPONSE] [HEADERS].


7.1.3.6.2. Implementation of POST Todos

Implement the processing of API(GET Todos) into postTodos method of TodoRestController that create new Todo Resource.

src/main/java/todo/api/todo/TodoRestController.java

package todo.api.todo;

import java.util.ArrayList;
import java.util.Collection;
import java.util.List;

import javax.inject.Inject;

import org.dozer.Mapper;
import org.springframework.http.HttpStatus;
import org.springframework.validation.annotation.Validated;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.ResponseStatus;
import org.springframework.web.bind.annotation.RestController;

import todo.domain.model.Todo;
import todo.domain.service.todo.TodoService;

@RestController
@RequestMapping("todos")
public class TodoRestController {

    @Inject
    TodoService todoService;
    @Inject
    Mapper beanMapper;

    @RequestMapping(method = RequestMethod.GET)
    @ResponseStatus(HttpStatus.OK)
    public List<TodoResource> getTodos() {
        Collection<Todo> todos = todoService.findAll();
        List<TodoResource> todoResources = new ArrayList<>();
        for (Todo todo : todos) {
            todoResources.add(beanMapper.map(todo, TodoResource.class));
        }
        return todoResources;
    }

    @RequestMapping(method = RequestMethod.POST) // (1)
    @ResponseStatus(HttpStatus.CREATED) // (2)
    public TodoResource postTodos(@RequestBody @Validated TodoResource todoResource) { // (3)
        Todo createdTodo = todoService.create(beanMapper.map(todoResource, Todo.class)); // (4)
        TodoResource createdTodoResponse = beanMapper.map(createdTodo, TodoResource.class); // (5)
        return createdTodoResponse; // (6)
    }

}
Sr. No Description
(1)
Set the RequestMethod.POST to method attribute for handling the POST request.
(2)
Specify @ResponseStatus annotation to the HTTP status code for response.
To set “201 Created” as a HTTP status, set the HttpStatus.CREATED to the value attribute.
(3)
In order to map the HTTP request Body(JSON) with JavaBean, grant @RequestBody annotation to the mapping targeted TodoResource class.
Furthermore, grant @Validated annotation for input check. It is necessary to handle exception separately.
(4)
Create new Todo resource by executing create method of TodoService after converting TodoResource into Todo class.
(5)
Converting Todo object created by create method of TodoService into TodoResource type that represent JSON response.
(6)
By returning the TodoResource object, it is serialized into JSON by MappingJackson2HttpMessageConverter defined in spring-mvc-rest.xml.

Check the operation of the implemented API using DHC.
Open the DHC, enter "localhost:8080/todo/api/v1/todos" in the URL and specify POST in method.
Enter the following JSON into [BODY] of the [REQUEST].
{
  "todoTitle": "Hello World!"
}

Furthermore, Add HTTP header by [+] button of [REQUEST] [HEADERS] and click “Send” button after setting [application/json] in the [Content-Type].

../_images/post-todos1.png

HTTP status returned “201 Created” and JSON of the newly created Todo resource displays in [Body] of [RESPONSE] part.

../_images/post-todos2.png

If GET Todos gets executed now, newly created Todo Resource returns as an array.

../_images/get-todos3.png

7.1.3.6.3. Implementation of GET Todo

Since method (findOne) for retrieving single item is not created in TodoService of the Tutorial (Todo Application), add the following highlighted parts in TodoService and TodoServiceImpl.

Add the definition of findOne method.
src/main/java/todo/domain/service/todo/TodoService.java
package todo.domain.service.todo;

import java.util.Collection;

import todo.domain.model.Todo;

public interface TodoService {
    Collection<Todo> findAll();

    Todo findOne(String todoId);

    Todo create(Todo todo);

    Todo finish(String todoId);

    void delete(String todoId);
}

Set a read-only transaction that is initiated at the time of calling findOne method.
src/main/java/todo/domain/service/todo/TodoServiceImpl.java
package todo.domain.service.todo;

import java.util.Collection;
import java.util.Date;
import java.util.UUID;

import javax.inject.Inject;

import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;
import org.terasoluna.gfw.common.exception.BusinessException;
import org.terasoluna.gfw.common.exception.ResourceNotFoundException;
import org.terasoluna.gfw.common.message.ResultMessage;
import org.terasoluna.gfw.common.message.ResultMessages;

import todo.domain.model.Todo;
import todo.domain.repository.todo.TodoRepository;

@Service
@Transactional
public class TodoServiceImpl implements TodoService {

    private static final long MAX_UNFINISHED_COUNT = 5;

    @Inject
    TodoRepository todoRepository;

    @Override
    @Transactional(readOnly = true)
    public Todo findOne(String todoId) {
        Todo todo = todoRepository.findOne(todoId);
        if (todo == null) {
            ResultMessages messages = ResultMessages.error();
            messages.add(ResultMessage
                    .fromText("[E404] The requested Todo is not found. (id="
                            + todoId + ")"));
            throw new ResourceNotFoundException(messages);
        }
        return todo;
    }

    @Override
    @Transactional(readOnly = true)
    public Collection<Todo> findAll() {
        return todoRepository.findAll();
    }

    @Override
    public Todo create(Todo todo) {
        long unfinishedCount = todoRepository.countByFinished(false);
        if (unfinishedCount >= MAX_UNFINISHED_COUNT) {
            ResultMessages messages = ResultMessages.error();
            messages.add(ResultMessage
                    .fromText("[E001] The count of un-finished Todo must not be over "
                            + MAX_UNFINISHED_COUNT + "."));
            throw new BusinessException(messages);
        }

        String todoId = UUID.randomUUID().toString();
        Date createdAt = new Date();

        todo.setTodoId(todoId);
        todo.setCreatedAt(createdAt);
        todo.setFinished(false);

        todoRepository.create(todo);
        /* REMOVE THIS LINE IF YOU USE JPA
            todoRepository.save(todo);
           REMOVE THIS LINE IF YOU USE JPA */

        return todo;
    }

    @Override
    public Todo finish(String todoId) {
        Todo todo = findOne(todoId);
        if (todo.isFinished()) {
            ResultMessages messages = ResultMessages.error();
            messages.add(ResultMessage
                    .fromText("[E002] The requested Todo is already finished. (id="
                            + todoId + ")"));
            throw new BusinessException(messages);
        }
        todo.setFinished(true);
        todoRepository.update(todo);
        /* REMOVE THIS LINE IF YOU USE JPA
            todoRepository.save(todo);
           REMOVE THIS LINE IF YOU USE JPA */
        return todo;
    }

    @Override
    public void delete(String todoId) {
        Todo todo = findOne(todoId);
        todoRepository.delete(todo);
    }
}

Implement the processing of retrieving single Todo Resource API(GET Todo) into getTodo method of TodoRestController .
src/main/java/todo/api/todo/TodoRestController.java
package todo.api.todo;

import java.util.ArrayList;
import java.util.Collection;
import java.util.List;

import javax.inject.Inject;

import org.dozer.Mapper;
import org.springframework.http.HttpStatus;
import org.springframework.validation.annotation.Validated;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.ResponseStatus;
import org.springframework.web.bind.annotation.RestController;

import todo.domain.model.Todo;
import todo.domain.service.todo.TodoService;

@RestController
@RequestMapping("todos")
public class TodoRestController {

    @Inject
    TodoService todoService;
    @Inject
    Mapper beanMapper;

    @RequestMapping(method = RequestMethod.GET)
    @ResponseStatus(HttpStatus.OK)
    public List<TodoResource> getTodos() {
        Collection<Todo> todos = todoService.findAll();
        List<TodoResource> todoResources = new ArrayList<>();
        for (Todo todo : todos) {
            todoResources.add(beanMapper.map(todo, TodoResource.class));
        }
        return todoResources;
    }

    @RequestMapping(method = RequestMethod.POST)
    @ResponseStatus(HttpStatus.CREATED)
    public TodoResource postTodos(@RequestBody @Validated TodoResource todoResource) {
        Todo createdTodo = todoService.create(beanMapper.map(todoResource, Todo.class));
        TodoResource createdTodoResponse = beanMapper.map(createdTodo, TodoResource.class);
        return createdTodoResponse;
    }

    @RequestMapping(value="{todoId}", method = RequestMethod.GET) // (1)
    @ResponseStatus(HttpStatus.OK)
    public TodoResource getTodo(@PathVariable("todoId") String todoId) { // (2)
        Todo todo = todoService.findOne(todoId); // (3)
        TodoResource todoResource = beanMapper.map(todo, TodoResource.class);
        return todoResource;
    }

}
Sr. No Description
(1)
In order to get the todoId from path, specify the path variable in the value attribute of the @RequestMapping annotation.
Set the RequestMethod.GET to method attribute for handling the GET request.
(2)
Specify the path variable name to retrieve todoId in the value attribute of the @PathVariable annotation.
(3)
You can use the todoId obtained from path variable to get one Todo resource.

Check the operation of the implemented API using DHC.
Open the DHC, enter "localhost:8080/todo/api/v1/todos/{todoId}" in the URL and specify GET in method.
Since it is necessary to enter the actual ID at {todoId}, run the POST Todos or GET Todos to get actual ID, copy & paste the todoId from the Response, and click the “Send” button.

HTTP status returned “200 OK” and JSON of the indicated Todo resource displays in [Body] of [RESPONSE] part.

../_images/get-todo1.png

7.1.3.6.4. Implementation of PUT Todo

Implement the processing of API(PUT Todo) into putTodo method of TodoRestController that updates(updating into completed status) one record of Todo Resource.

src/main/java/todo/api/todo/TodoRestController.java

package todo.api.todo;

import java.util.ArrayList;
import java.util.Collection;
import java.util.List;

import javax.inject.Inject;

import org.dozer.Mapper;
import org.springframework.http.HttpStatus;
import org.springframework.validation.annotation.Validated;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.ResponseStatus;
import org.springframework.web.bind.annotation.RestController;

import todo.domain.model.Todo;
import todo.domain.service.todo.TodoService;

@RestController
@RequestMapping("todos")
public class TodoRestController {

    @Inject
    TodoService todoService;
    @Inject
    Mapper beanMapper;

    @RequestMapping(method = RequestMethod.GET)
    @ResponseStatus(HttpStatus.OK)
    public List<TodoResource> getTodos() {
        Collection<Todo> todos = todoService.findAll();
        List<TodoResource> todoResources = new ArrayList<>();
        for (Todo todo : todos) {
            todoResources.add(beanMapper.map(todo, TodoResource.class));
        }
        return todoResources;
    }

    @RequestMapping(method = RequestMethod.POST)
    @ResponseStatus(HttpStatus.CREATED)
    public TodoResource postTodos(@RequestBody @Validated TodoResource todoResource) {
        Todo createdTodo = todoService.create(beanMapper.map(todoResource, Todo.class));
        TodoResource createdTodoResponse = beanMapper.map(createdTodo, TodoResource.class);
        return createdTodoResponse;
    }

    @RequestMapping(value="{todoId}", method = RequestMethod.GET)
    @ResponseStatus(HttpStatus.OK)
    public TodoResource getTodo(@PathVariable("todoId") String todoId) {
        Todo todo = todoService.findOne(todoId);
        TodoResource todoResource = beanMapper.map(todo, TodoResource.class);
        return todoResource;
    }

    @RequestMapping(value="{todoId}", method = RequestMethod.PUT) // (1)
    @ResponseStatus(HttpStatus.OK)
    public TodoResource putTodo(@PathVariable("todoId") String todoId) { // (2)
        Todo finishedTodo = todoService.finish(todoId); // (3)
        TodoResource finishedTodoResource = beanMapper.map(finishedTodo, TodoResource.class);
        return finishedTodoResource;
    }

}
Sr. No Description
(1)
In order to get the todoId from path, specify the path variable in the value attribute of the @RequestMappingannotation.
Set the RequestMethod.PUT to method attribute for handling the PUT request.
(2)
Specify the path variable name to retrieve todoId in the value attribute of the @PathVariable annotation.
(3)
You can use the todoId obtained from path variable to update the Todo resource in completed status.

Check the operation of the implemented API using DHC.
Open the DHC, enter "localhost:8080/todo/api/v1/todos/{todoId}" in the URL and specify PUT in method.
Since it is necessary to enter the actual ID at {todoId}, run the POST Todos or GET Todos to get actual ID, copy & paste the todoId from the Response, and click the “Send” button.
../_images/put-todo1.png

HTTP status returned “200 OK” and JSON of the modified Todo resource displays in [Body] of [RESPONSE] part.
finished is updated to true.
../_images/put-todo2.png

7.1.3.6.5. Implementation of DELETE Todo

Lastly, implement the processing of API(DELETE Todo) into deleteTodo method of TodoRestController that delete one record of Todo Resource.

src/main/java/todo/api/todo/TodoRestController.java

package todo.api.todo;

import java.util.ArrayList;
import java.util.Collection;
import java.util.List;

import javax.inject.Inject;

import org.dozer.Mapper;
import org.springframework.http.HttpStatus;
import org.springframework.validation.annotation.Validated;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.ResponseStatus;
import org.springframework.web.bind.annotation.RestController;

import todo.domain.model.Todo;
import todo.domain.service.todo.TodoService;

@RestController
@RequestMapping("todos")
public class TodoRestController {

    @Inject
    TodoService todoService;
    @Inject
    Mapper beanMapper;

    @RequestMapping(method = RequestMethod.GET)
    @ResponseStatus(HttpStatus.OK)
    public List<TodoResource> getTodos() {
        Collection<Todo> todos = todoService.findAll();
        List<TodoResource> todoResources = new ArrayList<>();
        for (Todo todo : todos) {
            todoResources.add(beanMapper.map(todo, TodoResource.class));
        }
        return todoResources;
    }

    @RequestMapping(method = RequestMethod.POST)
    @ResponseStatus(HttpStatus.CREATED)
    public TodoResource postTodos(@RequestBody @Validated TodoResource todoResource) {
        Todo createdTodo = todoService.create(beanMapper.map(todoResource, Todo.class));
        TodoResource createdTodoResponse = beanMapper.map(createdTodo, TodoResource.class);
        return createdTodoResponse;
    }

    @RequestMapping(value="{todoId}", method = RequestMethod.GET)
    @ResponseStatus(HttpStatus.OK)
    public TodoResource getTodo(@PathVariable("todoId") String todoId) {
        Todo todo = todoService.findOne(todoId);
        TodoResource todoResource = beanMapper.map(todo, TodoResource.class);
        return todoResource;
    }

    @RequestMapping(value="{todoId}", method = RequestMethod.PUT)
    @ResponseStatus(HttpStatus.OK)
    public TodoResource putTodo(@PathVariable("todoId") String todoId) {
        Todo finishedTodo = todoService.finish(todoId);
        TodoResource finishedTodoResource = beanMapper.map(finishedTodo, TodoResource.class);
        return finishedTodoResource;
    }

    @RequestMapping(value="{todoId}", method = RequestMethod.DELETE) // (1)
    @ResponseStatus(HttpStatus.NO_CONTENT) // (2)
    public void deleteTodo(@PathVariable("todoId") String todoId) { // (3)
        todoService.delete(todoId); // (4)
    }

}
Sr. No Description
(1)
In order to get the todoId from path, specify the path variable in the value attribute of the @RequestMapping annotation.
Set the RequestMethod.DELETE to method attribute for handling the DELETE request.
(2)
Specify @ResponseStatus annotation to the HTTP status code for response.
To set “204 No Content” as a HTTP status, set the HttpStatus.NO_CONTENT to the value attribute.
(3)
The type of return value is a void because there is no content to be returned in the case of DELETE.
(4)
You can use the todoId obtained from path variable to delete the Todo resource.

Check the operation of the implemented API using DHC.
Open the DHC, enter "localhost:8080/todo/api/v1/todos/{todoId}" in the URL and specify DELETE in method.
Since it is necessary to enter the actual ID at {todoId}, run the POST Todos or GET Todos to get actual ID, copy & paste the todoId from the Response, and click the “Send” button.
../_images/delete-todo1.png

HTTP status returned “204 No Content” and [Body] of [RESPONSE] is empty.

../_images/delete-todo2.png

Open the DHC, enter "localhost:8080/todo/api/v1/todos" in the URL and click the “Send” button by specify GET in method.
you can confirm that the Todo resource has been removed.
../_images/delete-todo3.png

7.1.3.7. Implementation of exception handling

In this tutorial, for easy understanding, the implementation of exception handling made a simpler than that are recommended in this guideline.
It is strongly recommended that the actual exception handling should be handled in a way described in the RESTful Web Service.

7.1.3.7.1. Change Domain layer implementation

In this tutorial, the error messages are retrieved from the property file based on error code.
Therefore, modify the implementation of the Service class as follows which is created at Tutorial (Todo Application) before implementing the exception handling.
Specify the error code instead of hard-coded error message.
src/main/java/todo/domain/service/todo/TodoServiceImpl.java
package todo.domain.service.todo;

import java.util.Collection;
import java.util.Date;
import java.util.UUID;

import javax.inject.Inject;

import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;
import org.terasoluna.gfw.common.exception.BusinessException;
import org.terasoluna.gfw.common.exception.ResourceNotFoundException;
import org.terasoluna.gfw.common.message.ResultMessages;

import todo.domain.model.Todo;
import todo.domain.repository.todo.TodoRepository;

@Service
@Transactional
public class TodoServiceImpl implements TodoService {

    private static final long MAX_UNFINISHED_COUNT = 5;

    @Inject
    TodoRepository todoRepository;

    @Override
    @Transactional(readOnly = true)
    public Todo findOne(String todoId) {
        Todo todo = todoRepository.findOne(todoId);
        if (todo == null) {
            ResultMessages messages = ResultMessages.error();
            messages.add("E404", todoId);
            throw new ResourceNotFoundException(messages);
        }
        return todo;
    }

    @Override
    @Transactional(readOnly = true)
    public Collection<Todo> findAll() {
        return todoRepository.findAll();
    }

    @Override
    public Todo create(Todo todo) {
        long unfinishedCount = todoRepository.countByFinished(false);
        if (unfinishedCount >= MAX_UNFINISHED_COUNT) {
            ResultMessages messages = ResultMessages.error();
            messages.add("E001", MAX_UNFINISHED_COUNT);
            throw new BusinessException(messages);
        }

        String todoId = UUID.randomUUID().toString();
        Date createdAt = new Date();

        todo.setTodoId(todoId);
        todo.setCreatedAt(createdAt);
        todo.setFinished(false);

        todoRepository.create(todo);
        /* REMOVE THIS LINE IF YOU USE JPA
            todoRepository.save(todo);
           REMOVE THIS LINE IF YOU USE JPA */

        return todo;
    }

    @Override
    public Todo finish(String todoId) {
        Todo todo = findOne(todoId);
        if (todo.isFinished()) {
            ResultMessages messages = ResultMessages.error();
            messages.add("E002", todoId);
            throw new BusinessException(messages);
        }
        todo.setFinished(true);
        todoRepository.update(todo);
        /* REMOVE THIS LINE IF YOU USE JPA
            todoRepository.save(todo);
           REMOVE THIS LINE IF YOU USE JPA */
        return todo;
    }

    @Override
    public void delete(String todoId) {
        Todo todo = findOne(todoId);
        todoRepository.delete(todo);
    }
}

7.1.3.7.2. Error message definition

In this tutorial, the error messages are retrieved from the property file based on error code.
Therefore, define the error code corresponding to the error messages in the message property file before implementing the exception handling.

Define the error code corresponding to the error messages of the processing result in the message property file.

../_images/application-messages.png

src/main/resources/i18n/application-messages.properties

e.xx.fw.5001 = Resource not found.

e.xx.fw.7001 = Illegal screen flow detected!
e.xx.fw.7002 = CSRF attack detected!
e.xx.fw.7003 = Access Denied detected!
e.xx.fw.7004 = Missing CSRF detected!

e.xx.fw.8001 = Business error occurred!

e.xx.fw.9001 = System error occurred!
e.xx.fw.9002 = Data Access error!

# typemismatch
typeMismatch="{0}" is invalid.
typeMismatch.int="{0}" must be an integer.
typeMismatch.double="{0}" must be a double.
typeMismatch.float="{0}" must be a float.
typeMismatch.long="{0}" must be a long.
typeMismatch.short="{0}" must be a short.
typeMismatch.boolean="{0}" must be a boolean.
typeMismatch.java.lang.Integer="{0}" must be an integer.
typeMismatch.java.lang.Double="{0}" must be a double.
typeMismatch.java.lang.Float="{0}" must be a float.
typeMismatch.java.lang.Long="{0}" must be a long.
typeMismatch.java.lang.Short="{0}" must be a short.
typeMismatch.java.lang.Boolean="{0}" is not a boolean.
typeMismatch.java.util.Date="{0}" is not a date.
typeMismatch.java.lang.Enum="{0}" is not a valid value.

# For this tutorial
E001 = [E001] The count of un-finished Todo must not be over {0}.
E002 = [E002] The requested Todo is already finished. (id={0})
E400 = [E400] The requested Todo contains invalid values.
E404 = [E404] The requested Todo is not found. (id={0})
E500 = [E500] System error occurred.
E999 = [E999] Error occurred. Caused by : {0}

Define the error messages corresponding to input check error codes, in Bean Validation message properties file.
Change the default message definition because the default message does not include the item name in the message
In this tutorial, only define the message corresponding to the rules (@NotNull and @Size) that are used in TodoResource class.
../_images/validation-messages.png

src/main/resources/ValidationMessages.properties

javax.validation.constraints.NotNull.message = {0} may not be null.
javax.validation.constraints.Size.message    = {0} size must be between {min} and {max}.

7.1.3.7.3. Create a package that contains the error handling class

Create a package for storing the error handling classes.
In this tutorial, creating a package for storing the todo.api.common.error error handling class.
../_images/exception-package.png

7.1.3.7.4. Creating REST API error handling class

The REST API error handling class is created by inheriting the org.springframework.web.servlet.mvc.method.annotation.ResponseEntityExceptionHandler provided by Spring MVC, adding the @ControllerAdvice annotation, and recommended to add (annotations = RestController.class) attribute in order to restrict to the REST API processing.
Below created the todo.api.common.error.RestGlobalExceptionHandler class inherited from the ResponseEntityExceptionHandler.
../_images/exception-handlingclass.png

src/main/java/todo/api/common/error/RestGlobalExceptionHandler.java

package todo.api.common.error;

import org.springframework.web.bind.annotation.ControllerAdvice;
import org.springframework.web.servlet.mvc.method.annotation.ResponseEntityExceptionHandler;

@ControllerAdvice
public class RestGlobalExceptionHandler extends ResponseEntityExceptionHandler {

}

7.1.3.7.5. Creating JavaBean for holding the REST API error information

Create ApiError class under the todo.api.common.error package for holding the error information generated by the REST API.
ApiError class converted into JSON and return to client.
../_images/exception-apierror.png

src/main/java/todo/api/common/error/ApiError.java

package todo.api.common.error;

import java.io.Serializable;
import java.util.ArrayList;
import java.util.List;

import com.fasterxml.jackson.annotation.JsonInclude;

public class ApiError implements Serializable {

    private static final long serialVersionUID = 1L;

    private final String code;

    private final String message;

    @JsonInclude(JsonInclude.Include.NON_EMPTY)
    private final String target;

    @JsonInclude(JsonInclude.Include.NON_EMPTY)
    private final List<ApiError> details = new ArrayList<>();

    public ApiError(String code, String message) {
        this(code, message, null);
    }

    public ApiError(String code, String message, String target) {
        this.code = code;
        this.message = message;
        this.target = target;
    }

    public String getCode() {
        return code;
    }

    public String getMessage() {
        return message;
    }

    public String getTarget() {
        return target;
    }

    public List<ApiError> getDetails() {
        return details;
    }

    public void addDetail(ApiError detail) {
        details.add(detail);
    }

}

7.1.3.7.6. Implementation of putting error information to the HTTP response BODY

By default ResponseEntityExceptionHandler configures only HTTP status (400 or 500 etc) but not configures the HTTP response BODY. Therefore, output the BODY by overidding the handleExceptionInternal method as follows.

src/main/java/todo/api/common/error/RestGlobalExceptionHandler.java

package todo.api.common.error;

import javax.inject.Inject;

import org.springframework.context.MessageSource;
import org.springframework.http.HttpHeaders;
import org.springframework.http.HttpStatus;
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.ControllerAdvice;
import org.springframework.web.context.request.WebRequest;
import org.springframework.web.servlet.mvc.method.annotation.ResponseEntityExceptionHandler;

@ControllerAdvice
public class RestGlobalExceptionHandler extends ResponseEntityExceptionHandler {

    @Inject
    MessageSource messageSource;

    @Override
    protected ResponseEntity<Object> handleExceptionInternal(Exception ex,
            Object body, HttpHeaders headers, HttpStatus status,
            WebRequest request) {
        Object responseBody = body;
        if (body == null) {
            responseBody = createApiError(request, "E999", ex.getMessage());
        }
        return ResponseEntity.status(status).headers(headers).body(responseBody);
    }

    private ApiError createApiError(WebRequest request, String errorCode,
            Object... args) {
        return new ApiError(errorCode, messageSource.getMessage(errorCode,
                args, request.getLocale()));
    }

}
By performing the above implementation, the error information is logged in to HTTP response BODY which was handled by the ResponseEntityExceptionHandler .
About the exception handled by ResponseEntityExceptionHandler , refer HTTP response code set by DefaultHandlerExceptionResolver.

Check the operation of the implemented error handling using DHC.
Open the DHC, enter "localhost:8080/todo/api/v1/todos" in the URL and click the “Send” button after specifying PUT in method.

HTTP status returned “405 Method Not Allowed” and the JSON error information displays in [Body] of [RESPONSE] part.

../_images/exception-genericerror.png

7.1.3.7.7. Error handling of Input errors

Type of input errors as follows.

  • org.springframework.web.bind.MethodArgumentNotValidException
  • org.springframework.validation.BindException
  • org.springframework.http.converter.HttpMessageNotReadableException
  • org.springframework.beans.TypeMismatchException
In this tutorial, implementing the MethodArgumentNotValidException error handling.
The MethodArgumentNotValidException is an exception that occurs if there is any input error in the data stored in HTTP request BODY.

src/main/java/todo/api/common/error/RestGlobalExceptionHandler.java

package todo.api.common.error;

import javax.inject.Inject;

import org.springframework.context.MessageSource;
import org.springframework.context.support.DefaultMessageSourceResolvable;
import org.springframework.http.HttpHeaders;
import org.springframework.http.HttpStatus;
import org.springframework.http.ResponseEntity;
import org.springframework.validation.FieldError;
import org.springframework.validation.ObjectError;
import org.springframework.web.bind.MethodArgumentNotValidException;
import org.springframework.web.bind.annotation.ControllerAdvice;
import org.springframework.web.context.request.WebRequest;
import org.springframework.web.servlet.mvc.method.annotation.ResponseEntityExceptionHandler;

@ControllerAdvice
public class RestGlobalExceptionHandler extends ResponseEntityExceptionHandler {

    @Inject
    MessageSource messageSource;

    @Override
    protected ResponseEntity<Object> handleExceptionInternal(Exception ex,
            Object body, HttpHeaders headers, HttpStatus status,
            WebRequest request) {
        Object responseBody = body;
        if (body == null) {
            responseBody = createApiError(request, "E999", ex.getMessage());
        }
        return ResponseEntity.status(status).headers(headers).body(responseBody);
    }

    private ApiError createApiError(WebRequest request, String errorCode,
            Object... args) {
        return new ApiError(errorCode, messageSource.getMessage(errorCode,
                args, request.getLocale()));
    }

    @Override
    protected ResponseEntity<Object> handleMethodArgumentNotValid(
            MethodArgumentNotValidException ex, HttpHeaders headers,
            HttpStatus status, WebRequest request) {
        ApiError apiError = createApiError(request, "E400");
        for (FieldError fieldError : ex.getBindingResult().getFieldErrors()) {
            apiError.addDetail(createApiError(request, fieldError, fieldError
                    .getField()));
        }
        for (ObjectError objectError : ex.getBindingResult().getGlobalErrors()) {
            apiError.addDetail(createApiError(request, objectError, objectError
                    .getObjectName()));
        }
        return handleExceptionInternal(ex, apiError, headers, status, request);
    }

    private ApiError createApiError(WebRequest request,
            DefaultMessageSourceResolvable messageSourceResolvable,
            String target) {
        return new ApiError(messageSourceResolvable.getCode(), messageSource
                .getMessage(messageSourceResolvable, request.getLocale()), target);
    }

}

Check the operation of the implemented error handling using DHC.
Open the DHC, enter "localhost:8080/todo/api/v1/todos" in the URL and specify POST in method.
Enter below JSON in [BODY] of the [REQUEST].
{
  "todoTitle": null
}

Furthermore, Add HTTP header by [+] button of [REQUEST] [HEADERS] and click “Send” button after setting [application/json] in the [Content-Type].

HTTP status returned “400 Bad Request” and JSON error information displays in [Body] of [RESPONSE] part.
Since todoTitle is required field, required error occurred.
../_images/exception-inputerror.png

7.1.3.7.8. Business exception error handling

Handling a business exception by adding org.terasoluna.gfw.common.exception.BusinessException method in the RestGlobalExceptionHandler .

Set “409 Conflict” in HTTP status if business exception occurred.

src/main/java/todo/api/common/error/RestGlobalExceptionHandler.java

package todo.api.common.error;

import javax.inject.Inject;

import org.springframework.context.MessageSource;
import org.springframework.context.support.DefaultMessageSourceResolvable;
import org.springframework.http.HttpHeaders;
import org.springframework.http.HttpStatus;
import org.springframework.http.ResponseEntity;
import org.springframework.validation.FieldError;
import org.springframework.validation.ObjectError;
import org.springframework.web.bind.MethodArgumentNotValidException;
import org.springframework.web.bind.annotation.ControllerAdvice;
import org.springframework.web.bind.annotation.ExceptionHandler;
import org.springframework.web.context.request.WebRequest;
import org.springframework.web.servlet.mvc.method.annotation.ResponseEntityExceptionHandler;
import org.terasoluna.gfw.common.exception.BusinessException;
import org.terasoluna.gfw.common.exception.ResultMessagesNotificationException;
import org.terasoluna.gfw.common.message.ResultMessage;

@ControllerAdvice
public class RestGlobalExceptionHandler extends ResponseEntityExceptionHandler {

    @Inject
    MessageSource messageSource;

    @Override
    protected ResponseEntity<Object> handleExceptionInternal(Exception ex,
            Object body, HttpHeaders headers, HttpStatus status,
            WebRequest request) {
        Object responseBody = body;
        if (body == null) {
            responseBody = createApiError(request, "E999", ex.getMessage());
        }
        return ResponseEntity.status(status).headers(headers).body(responseBody);
    }

    private ApiError createApiError(WebRequest request, String errorCode,
            Object... args) {
        return new ApiError(errorCode, messageSource.getMessage(errorCode,
                args, request.getLocale()));
    }

    @Override
    protected ResponseEntity<Object> handleMethodArgumentNotValid(
            MethodArgumentNotValidException ex, HttpHeaders headers,
            HttpStatus status, WebRequest request) {
        ApiError apiError = createApiError(request, "E400");
        for (FieldError fieldError : ex.getBindingResult().getFieldErrors()) {
            apiError.addDetail(createApiError(request, fieldError, fieldError
                    .getField()));
        }
        for (ObjectError objectError : ex.getBindingResult().getGlobalErrors()) {
            apiError.addDetail(createApiError(request, objectError, objectError
                    .getObjectName()));
        }
        return handleExceptionInternal(ex, apiError, headers, status, request);
    }

    private ApiError createApiError(WebRequest request,
            DefaultMessageSourceResolvable messageSourceResolvable,
            String target) {
        return new ApiError(messageSourceResolvable.getCode(), messageSource
                .getMessage(messageSourceResolvable, request.getLocale()), target);
    }

    @ExceptionHandler(BusinessException.class)
    public ResponseEntity<Object> handleBusinessException(BusinessException ex,
            WebRequest request) {
        return handleResultMessagesNotificationException(ex, new HttpHeaders(),
                HttpStatus.CONFLICT, request);
    }

    private ResponseEntity<Object> handleResultMessagesNotificationException(
            ResultMessagesNotificationException ex, HttpHeaders headers,
            HttpStatus status, WebRequest request) {
        ResultMessage message = ex.getResultMessages().iterator().next();
        ApiError apiError = createApiError(request, message.getCode(), message
                .getArgs());
        return handleExceptionInternal(ex, apiError, headers, status, request);
    }

}

Check the operation of the implemented error handling using DHC.
Open the DHC, enter "localhost:8080/todo/api/v1/todos/{todoId}" in the URL and specify PUT in method.
Since it is necessary to enter the actual ID at {todoId}, run the POST Todos or GET Todos to get actual ID, copy & paste the todoId from the Response, and click the “Send” button twice.
Specify un-completed todoId of the Todos.

HTTP status returned “409 Conflict” as a response of the 2nd request and JSON error information displays in [Body] of [RESPONSE] part.

../_images/exception-businesserror.png

7.1.3.7.9. Resource not found exception error handling

Resource not found exception handles by adding org.terasoluna.gfw.common.exception.ResourceNotFoundException method in the RestGlobalExceptionHandler.

Set “404 NotFound” in HTTP status if Resource not found exception occurred.

src/main/java/todo/api/common/error/RestGlobalExceptionHandler.java

package todo.api.common.error;

import javax.inject.Inject;

import org.springframework.context.MessageSource;
import org.springframework.context.support.DefaultMessageSourceResolvable;
import org.springframework.http.HttpHeaders;
import org.springframework.http.HttpStatus;
import org.springframework.http.ResponseEntity;
import org.springframework.validation.FieldError;
import org.springframework.validation.ObjectError;
import org.springframework.web.bind.MethodArgumentNotValidException;
import org.springframework.web.bind.annotation.ControllerAdvice;
import org.springframework.web.bind.annotation.ExceptionHandler;
import org.springframework.web.context.request.WebRequest;
import org.springframework.web.servlet.mvc.method.annotation.ResponseEntityExceptionHandler;
import org.terasoluna.gfw.common.exception.BusinessException;
import org.terasoluna.gfw.common.exception.ResourceNotFoundException;
import org.terasoluna.gfw.common.exception.ResultMessagesNotificationException;
import org.terasoluna.gfw.common.message.ResultMessage;

@ControllerAdvice
public class RestGlobalExceptionHandler extends ResponseEntityExceptionHandler {

    @Inject
    MessageSource messageSource;

    @Override
    protected ResponseEntity<Object> handleExceptionInternal(Exception ex,
            Object body, HttpHeaders headers, HttpStatus status,
            WebRequest request) {
        Object responseBody = body;
        if (body == null) {
            responseBody = createApiError(request, "E999", ex.getMessage());
        }
        return ResponseEntity.status(status).headers(headers).body(responseBody);
    }

    private ApiError createApiError(WebRequest request, String errorCode,
            Object... args) {
        return new ApiError(errorCode, messageSource.getMessage(errorCode,
                args, request.getLocale()));
    }

    @Override
    protected ResponseEntity<Object> handleMethodArgumentNotValid(
            MethodArgumentNotValidException ex, HttpHeaders headers,
            HttpStatus status, WebRequest request) {
        ApiError apiError = createApiError(request, "E400");
        for (FieldError fieldError : ex.getBindingResult().getFieldErrors()) {
            apiError.addDetail(createApiError(request, fieldError, fieldError
                    .getField()));
        }
        for (ObjectError objectError : ex.getBindingResult().getGlobalErrors()) {
            apiError.addDetail(createApiError(request, objectError, objectError
                    .getObjectName()));
        }
        return handleExceptionInternal(ex, apiError, headers, status, request);
    }

    private ApiError createApiError(WebRequest request,
            DefaultMessageSourceResolvable messageSourceResolvable,
            String target) {
        return new ApiError(messageSourceResolvable.getCode(), messageSource
                .getMessage(messageSourceResolvable, request.getLocale()), target);
    }

    @ExceptionHandler(BusinessException.class)
    public ResponseEntity<Object> handleBusinessException(BusinessException ex,
            WebRequest request) {
        return handleResultMessagesNotificationException(ex, new HttpHeaders(),
                HttpStatus.CONFLICT, request);
    }

    private ResponseEntity<Object> handleResultMessagesNotificationException(
            ResultMessagesNotificationException ex, HttpHeaders headers,
            HttpStatus status, WebRequest request) {
        ResultMessage message = ex.getResultMessages().iterator().next();
        ApiError apiError = createApiError(request, message.getCode(), message
                .getArgs());
        return handleExceptionInternal(ex, apiError, headers, status, request);
    }

    @ExceptionHandler(ResourceNotFoundException.class)
    public ResponseEntity<Object> handleResourceNotFoundException(
            ResourceNotFoundException ex, WebRequest request) {
        return handleResultMessagesNotificationException(ex, new HttpHeaders(),
                HttpStatus.NOT_FOUND, request);
    }

}

Check the operation of the implemented error handling using DHC.
Open the DHC, enter "localhost:8080/todo/api/v1/todos/{todoId}" in the URL and specify GET in method.
Specifying the ID that does not exist in {todoId} portion and click “Send” button.

HTTP status returned “404 Not Found” and JSON error information displays in [Body] of [RESPONSE] part.

../_images/exception-notfound.png

7.1.3.7.10. System exception error handling

Lastly, System exception handles by adding java.lang.Exception method in the RestGlobalExceptionHandler.

Set “500 InternalServerError” in HTTP status if System exception occurred.

src/main/java/todo/api/common/error/RestGlobalExceptionHandler.java

package todo.api.common.error;

import javax.inject.Inject;

import org.springframework.context.MessageSource;
import org.springframework.context.support.DefaultMessageSourceResolvable;
import org.springframework.http.HttpHeaders;
import org.springframework.http.HttpStatus;
import org.springframework.http.ResponseEntity;
import org.springframework.validation.FieldError;
import org.springframework.validation.ObjectError;
import org.springframework.web.bind.MethodArgumentNotValidException;
import org.springframework.web.bind.annotation.ControllerAdvice;
import org.springframework.web.bind.annotation.ExceptionHandler;
import org.springframework.web.context.request.WebRequest;
import org.springframework.web.servlet.mvc.method.annotation.ResponseEntityExceptionHandler;
import org.terasoluna.gfw.common.exception.BusinessException;
import org.terasoluna.gfw.common.exception.ResourceNotFoundException;
import org.terasoluna.gfw.common.exception.ResultMessagesNotificationException;
import org.terasoluna.gfw.common.message.ResultMessage;

@ControllerAdvice
public class RestGlobalExceptionHandler extends ResponseEntityExceptionHandler {

    @Inject
    MessageSource messageSource;

    @Override
    protected ResponseEntity<Object> handleExceptionInternal(Exception ex,
            Object body, HttpHeaders headers, HttpStatus status,
            WebRequest request) {
        Object responseBody = body;
        if (body == null) {
            responseBody = createApiError(request, "E999", ex.getMessage());
        }
        return ResponseEntity.status(status).headers(headers).body(responseBody);
    }

    private ApiError createApiError(WebRequest request, String errorCode,
            Object... args) {
        return new ApiError(errorCode, messageSource.getMessage(errorCode,
                args, request.getLocale()));
    }

    @Override
    protected ResponseEntity<Object> handleMethodArgumentNotValid(
            MethodArgumentNotValidException ex, HttpHeaders headers,
            HttpStatus status, WebRequest request) {
        ApiError apiError = createApiError(request, "E400");
        for (FieldError fieldError : ex.getBindingResult().getFieldErrors()) {
            apiError.addDetail(createApiError(request, fieldError, fieldError
                    .getField()));
        }
        for (ObjectError objectError : ex.getBindingResult().getGlobalErrors()) {
            apiError.addDetail(createApiError(request, objectError, objectError
                    .getObjectName()));
        }
        return handleExceptionInternal(ex, apiError, headers, status, request);
    }

    private ApiError createApiError(WebRequest request,
            DefaultMessageSourceResolvable messageSourceResolvable,
            String target) {
        return new ApiError(messageSourceResolvable.getCode(), messageSource
                .getMessage(messageSourceResolvable, request.getLocale()), target);
    }

    @ExceptionHandler(BusinessException.class)
    public ResponseEntity<Object> handleBusinessException(BusinessException ex,
            WebRequest request) {
        return handleResultMessagesNotificationException(ex, new HttpHeaders(),
                HttpStatus.CONFLICT, request);
    }

    private ResponseEntity<Object> handleResultMessagesNotificationException(
            ResultMessagesNotificationException ex, HttpHeaders headers,
            HttpStatus status, WebRequest request) {
        ResultMessage message = ex.getResultMessages().iterator().next();
        ApiError apiError = createApiError(request, message.getCode(), message
                .getArgs());
        return handleExceptionInternal(ex, apiError, headers, status, request);
    }

    @ExceptionHandler(ResourceNotFoundException.class)
    public ResponseEntity<Object> handleResourceNotFoundException(
            ResourceNotFoundException ex, WebRequest request) {
        return handleResultMessagesNotificationException(ex, new HttpHeaders(),
                HttpStatus.NOT_FOUND, request);
    }

    @ExceptionHandler(Exception.class)
    public ResponseEntity<Object> handleSystemError(Exception ex,
            WebRequest request) {
        ApiError apiError = createApiError(request, "E500");
        return handleExceptionInternal(ex, apiError, new HttpHeaders(),
                HttpStatus.INTERNAL_SERVER_ERROR, request);
    }

}

Check the operation of the implemented error handling using DHC.
In order to generate a system error, boot the application in the state of Database tables are not created.

src/main/resources/META-INF/spring/todo-infra.properties

database=H2
#database.url=jdbc:h2:mem:todo;DB_CLOSE_DELAY=-1;INIT=create table if not exists todo(todo_id varchar(36) primary key, todo_title varchar(30), finished boolean, created_at timestamp)
database.url=jdbc:h2:mem:todo;DB_CLOSE_DELAY=-1
database.username=sa
database.password=
database.driverClassName=org.h2.Driver
# connection pool
cp.maxActive=96
cp.maxIdle=16
cp.minIdle=0
cp.maxWait=60000

Open the DHC, enter "localhost:8080/todo/api/v1/todos/" in the URL and click the “Send” button after specifying GET in method.

HTTP status returned “500 Internal Server Error” and JSON error information displays in [Body] of [RESPONSE] part.

../_images/exception-systemerror.png

Note

In case of system error occurred, it is recommended to set a simple error message from which cause of error can not be identified while error message returning to the client. When you set the error message from which cause of error is identified, there is a possibility to exposes the vulnerability of the system to the client and may cause security issues.

It is good to flush the cause of an error into error analysis log. The default setting of Blank project has been outputting the log by ExceptionLogger provided in the common library therefore setting and implementation for outputting the log is not required.

The log output by ExceptionLogger is as follows.

The cause of the system error can be understood that the Todo table is not exist.

date:2015-01-19 02:08:47        thread:tomcat-http--4   X-Track:aadf5822205d423c95a6531f2f76036f        level:ERROR     logger:o.t.gfw.common.exception.ExceptionLogger         message:[e.xx.fw.9002]
### Error querying database.  Cause: org.h2.jdbc.JdbcSQLException: Table "TODO" not found; SQL statement:
SELECT
            todo_id,
            todo_title,
            finished,
            created_at
        FROM
            todo [42102-182]
### The error may exist in todo/domain/repository/todo/TodoRepository.xml
### The error may involve todo.domain.repository.todo.TodoRepository.findAll
### The error occurred while executing a query

... (omitted)

7.1.4. In the end...

In this tutorial, following contents have been learnt.

  • How to develop basic RESTful Web service by TERASOLUNA Server Framework for Java (5.x)
  • Implementation of Controller class that offers REST API(GET, POST, PUT, DELETE)
  • Cross conversion method of JavaBean and JSON
  • Error message definition method
  • Method of handling a variety of exception with Spring MVC

Here, explained how to implement the basic RESTful Web Services. To learn more about the architecture and design guidelines etc, Refer [RESTful Web Service].