[转]Spring REST

http://www.cnblogs.com/hoojo/archive/2011/06/10/2077422.html
Spring REST
前面介绍过Spring的MVC结合不同的view显示不同的数据，如：结合json的view显示json、结合xml的view显示xml文档。那么这些数据除了在WebBrowser中用JavaScript来调用以外，还可以用远程服务器的Java程序、C#程序来调用。也就是说现在的程序不仅在BS中能调用，在CS中同样也能调用，不过你需要借助RestTemplate这个类来完成。RestTemplate有点类似于一个WebService客户端请求的模版，可以调用http请求的WebService，并将结果转换成相应的对象类型。至少你可以这样理解！



上一次博文介绍SpringMVC结合不同的View，显示不同的数据。http://www.cnblogs.com/hoojo/archive/2011/04/29/2032571.html



Email：hoojo_@126.com

Blog：http://blog.youkuaiyun.com/IBM_hoojo

http://hoojo.cnblogs.com/



一、准备工作
1、 下载jar包

spring各版本jar下载地址：http://ebr.springsource.com/repository/app/library/detail?name=org.springframework.spring

相关的依赖包也可以在这里找到：http://ebr.springsource.com/repository/app/library



2、 需要jar包如下





3、 当前工程的web.xml配置

<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.4"
xmlns="http://java.sun.com/xml/ns/j2ee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee
http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd">

<!-- 配置Spring核心控制器 -->
<servlet>
<servlet-name>dispatcher</servlet-name>
<servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
<init-param>
<param-name>contextConfigLocation</param-name>
<param-value>/WEB-INF/dispatcher.xml</param-value>
</init-param>
<load-on-startup>1</load-on-startup>
</servlet>

<servlet-mapping>
<servlet-name>dispatcher</servlet-name>
<url-pattern>*.do</url-pattern>
</servlet-mapping>

<welcome-file-list>
<welcome-file>index.jsp</welcome-file>
</welcome-file-list>
</web-app>

4、 WEB-INF中的dispatcher.xml配置

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:mvc="http://www.springframework.org/schema/mvc"
xmlns:context="http://www.springframework.org/schema/context"
xmlns:util="http://www.springframework.org/schema/util"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
http://www.springframework.org/schema/mvc
http://www.springframework.org/schema/mvc/spring-mvc-3.0.xsd
http://www.springframework.org/schema/context
http://www.springframework.org/schema/context/spring-context-3.0.xsd
http://www.springframework.org/schema/util
http://www.springframework.org/schema/util/spring-util-3.0.xsd">

<context:component-scan base-package="com.hoo.*">
<!-- 忽略这个类 -->
<context:exclude-filter type="assignable" expression="com.hoo.client.RESTClient"/>
</context:component-scan>

<!-- annotation的方法映射适配器 -->
<bean id="handlerAdapter" class="org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter"/>

<!-- xml视图，XStreamMarshaller，可以转换任何形式的java对象 -->
<bean name="xStreamMarshallingView" class="org.springframework.web.servlet.view.xml.MarshallingView">
<property name="marshaller">
<bean class="org.springframework.oxm.xstream.XStreamMarshaller">
<!-- 为了初始化XStreamMarshaller，这个类会把我们接口中得到结果以XML文档形式展现出来 -->
<property name="autodetectAnnotations" value="true"/>
</bean>
</property>
</bean>

<!-- 视图解析器，根据视图的名称new ModelAndView(name)，在配置文件查找对应的bean配置 -->
<bean class="org.springframework.web.servlet.view.BeanNameViewResolver">
<property name="order" value="3"/>
</bean>

<!-- annotation默认的方法映射适配器 -->
<bean id="handlerMapping" class="org.springframework.web.servlet.mvc.annotation.DefaultAnnotationHandlerMapping">
<property name="order" value="1" />
</bean>

</beans>

5、 启动后，可以看到index.jsp 没有出现异常或错误。那么当前SpringMVC的配置就成功了。



二、REST控制器实现
REST控制器主要完成CRUD操作，也就是对于http中的post、get、put、delete。

还有其他的操作，如head、options、trace。

具体代码：

package com.hoo.controller;

import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.servlet.ModelAndView;

/**
* <b>function:</b>SpringMVC REST示例
* @author hoojo
* @createDate 2011-6-9 上午11:34:08
* @file RESTController.java
* @package com.hoo.controller
* @project SpringRestWS
* @blog http://blog.youkuaiyun.com/IBM_hoojo
* @email hoojo_@126.com
* @version 1.0
*/
@RequestMapping("/restful")
@Controller
public class RESTController {

@RequestMapping(value = "/show", method = RequestMethod.GET)
public ModelAndView show() {
System.out.println("show");
ModelAndView model = new ModelAndView("xStreamMarshallingView");
model.addObject("show method");
return model;
}

@RequestMapping(value = "/get/{id}", method = RequestMethod.GET)
public ModelAndView getUserById(@PathVariable String id) {
System.out.println("getUserById-" + id);
ModelAndView model = new ModelAndView("xStreamMarshallingView");
model.addObject("getUserById method -" + id);
return model;
}

@RequestMapping(value = "/add", method = RequestMethod.POST)
public ModelAndView addUser(String user) {
System.out.println("addUser-" + user);
ModelAndView model = new ModelAndView("xStreamMarshallingView");
model.addObject("addUser method -" + user);
return model;
}

@RequestMapping(value = "/edit", method = RequestMethod.PUT)
public ModelAndView editUser(String user) {
System.out.println("editUser-" + user);
ModelAndView model = new ModelAndView("xStreamMarshallingView");
model.addObject("editUser method -" + user);
return model;
}

@RequestMapping(value = "/remove/{id}", method = RequestMethod.DELETE)
public ModelAndView removeUser(@PathVariable String id) {
System.out.println("removeUser-" + id);
ModelAndView model = new ModelAndView("xStreamMarshallingView");
model.addObject("removeUser method -" + id);
return model;
}
}

上面的方法对应的http操作：

/show -> get 查询
/get/id -> get 查询
/add -> post 添加
/edit -> put 修改
/remove/id -> delete 删除

在这个方法中，就可以看到RESTful风格的url资源标识

@RequestMapping(value = "/get/{id}", method = RequestMethod.GET)
public ModelAndView getUserById(@PathVariable String id) {
System.out.println("getUserById-" + id);
ModelAndView model = new ModelAndView("xStreamMarshallingView");
model.addObject("getUserById method -" + id);
return model;
}

value=”/get/{id}”就是url中包含get，并且带有id参数的get请求，就会执行这个方法。这个url在请求的时候，会通过Annotation的@PathVariable来将url中的id值设置到getUserById的参数中去。 ModelAndView返回的视图是xStreamMarshallingView是一个xml视图，执行当前请求后，会显示一篇xml文档。文档的内容是添加到model中的值。



三、利用RestTemplate调用REST资源
代码如下：

package com.hoo.client;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;
import org.springframework.web.client.RestTemplate;

/**
* <b>function:</b>RestTemplate调用REST资源
* @author hoojo
* @createDate 2011-6-9 上午11:56:16
* @file RESTClient.java
* @package com.hoo.client
* @project SpringRestWS
* @blog http://blog.youkuaiyun.com/IBM_hoojo
* @email hoojo_@126.com
* @version 1.0
*/
@Component
public class RESTClient {

@Autowired
private RestTemplate template;

private final static String url = "http://localhost:8080/SpringRestWS/restful/";

public String show() {
return template.getForObject(url + "show.do", String.class, new String[]{});
}

public String getUserById(String id) {
return template.getForObject(url + "get/{id}.do", String.class, id);
}

public String addUser(String user) {
return template.postForObject(url + "add.do?user={user}", null, String.class, user);
}

public String editUser(String user) {
template.put(url + "edit.do?user={user}", null, user);
return user;
}

public String removeUser(String id) {
template.delete(url + "/remove/{id}.do", id);
return id;
}
}

RestTemplate的getForObject完成get请求、postForObject完成post请求、put对应的完成put请求、delete完成delete请求；还有execute可以执行任何请求的方法，需要你设置RequestMethod来指定当前请求类型。

RestTemplate.getForObject(String url, Class<String> responseType, String... urlVariables)

参数url是http请求的地址，参数Class是请求响应返回后的数据的类型，最后一个参数是请求中需要设置的参数。

template.getForObject(url + "get/{id}.do", String.class, id);

如上面的参数是{id}，返回的是一个string类型，设置的参数是id。最后执行该方法会返回一个String类型的结果。



下面建立一个测试类，完成对RESTClient的测试。代码如下：

package com.hoo.client;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.test.context.ContextConfiguration;
import org.springframework.test.context.junit38.AbstractJUnit38SpringContextTests;

/**
* <b>function:</b>RESTClient TEST
* @author hoojo
* @createDate 2011-6-9 下午03:50:21
* @file RESTClientTest.java
* @package com.hoo.client
* @project SpringRestWS
* @blog http://blog.youkuaiyun.com/IBM_hoojo
* @email hoojo_@126.com
* @version 1.0
*/
@ContextConfiguration("classpath:applicationContext-*.xml")
public class RESTClientTest extends AbstractJUnit38SpringContextTests {

@Autowired
private RESTClient client;

public void testShow() {
System.out.println(client.show());
}

public void testGetUserById() {
System.out.println(client.getUserById("abc"));
}

public void testAddUser() {
System.out.println(client.addUser("jack"));
}

public void testEditUser() {
System.out.println(client.editUser("tom"));
}

public void testRemoveUser() {
System.out.println(client.removeUser("aabb"));
}
}

我们需要在src目录下添加applicationContext-beans.xml完成对restTemplate的配置。restTemplate需要配置MessageConvert将返回的xml文档进行转换，解析成JavaObject。

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:context="http://www.springframework.org/schema/context"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
http://www.springframework.org/schema/context
http://www.springframework.org/schema/context/spring-context-3.0.xsd">

<context:component-scan base-package="com.hoo.*"/>

<bean id="restTemplate" class="org.springframework.web.client.RestTemplate">
<property name="messageConverters">
<list>
<bean class="org.springframework.http.converter.xml.MarshallingHttpMessageConverter">
<property name="marshaller" ref="xStreamMarshaller"/>
<property name="unmarshaller" ref="xStreamMarshaller"/>
</bean>
</list>
</property>
</bean>

<bean id="xStreamMarshaller" class="org.springframework.oxm.xstream.XStreamMarshaller">
<property name="annotatedClasses">
<array>
</array>
</property>
</bean>
</beans>

上面配置了xStreamMarshaller是和RESTController中的ModelAndView的view对应的。因为那边是用xStreamMarshaller进行编组的，所以RestTemplate这边也需要用它来解组。RestTemplate还指出其他的MarshallingHttpMessageConverter；