前面介紹過Spring的MVC結合不同的view顯示不同的資料，如：結合json的view顯示json、結合xml的view顯示xml文件。那麼這些資料除了在WebBrowser中用JavaScript來呼叫以外，還可以用遠端伺服器的Java程式、C#程式來呼叫。也就是說現在的程式不僅在BS中能呼叫，在CS中同樣也能呼叫，不過你需要藉助RestTemplate這個類來完成。RestTemplate有點類似於一個WebService客戶端請求的模版，可以呼叫http請求的WebService，並將結果轉換成相應的物件型別。至少你可以這樣理解！

一、準備工作

1、 下載jar包

2、 需要jar包如下

3、 當前工程的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">

    <servlet
 
>

        <servlet-name>dispatcherservlet-name>

        <servlet-class>org.springframework.web.servlet.DispatcherServletservlet-class>

        <init-param>

            <param-name>contextConfigLocationparam-name>

            <param-value>/WEB-INF/dispatcher.xmlparam-value
 
>

        init-param>

        <load-on-startup>1load-on-startup>

    servlet>

    <servlet-mapping>

        <servlet-name>dispatcherservlet-name>

        <url-pattern>*.dourl-pattern>

    servlet-mapping>

    <welcome-file-list>

      <welcome-file>index.jspwelcome-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.*">

        <context:exclude-filter type="assignable" expression="com.hoo.client.RESTClient"/>

    context:component-scan>

    <bean id="handlerAdapter" class="org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter"/>

    <bean name="xStreamMarshallingView" class="org.springframework.web.servlet.view.xml.MarshallingView">

        <property name="marshaller">

            <bean class="org.springframework.oxm.xstream.XStreamMarshaller">  

                <property name="autodetectAnnotations" value="true"/>  

            bean>  

        property>

    bean>

    <bean class="org.springframework.web.servlet.view.BeanNameViewResolver">

        <property name="order" value="3"/>

    bean>

    <bean id="handlerMapping" class="org.springframework.web.servlet.mvc.annotation.DefaultAnnotationHandlerMapping">

        <property name="order" value="1" />

    bean>

beans>

5、 啟動後，可以看到index.jsp 沒有出現異常或錯誤。那麼當前SpringMVC的配置就成功了。

二、REST控制器實現

REST控制器主要完成CRUD操作，也就是對於http中的post、get、put、delete。

還有其他的操作，如head、options、trace。

具體程式碼：

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;

/**

 * function: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.csdn.net/IBM_hoojo

 * @email [email protected]

 * @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;

    }

}

上面的方法對應的http操作：

/show -> get 查詢

/get/id -> get 查詢

/add -> post 新增

/edit -> put 修改

/remove/id -> delete 刪除

在這個方法中，就可以看到RESTful風格的url資源標識

@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，並且帶有id引數的get請求，就會執行這個方法。這個url在請求的時候，會通過Annotation的@PathVariable來將url中的id值設定到getUserById的引數中去。 ModelAndView返回的檢視是xStreamMarshallingView是一個xml檢視，執行當前請求後，會顯示一篇xml文件。文件的內容是新增到model中的值。

三、利用RestTemplate呼叫REST資源

程式碼如下：

package com.hoo.client;

import org.springframework.beans.factory.annotation.Autowired;

import org.springframework.stereotype.Component;

import org.springframework.web.client.RestTemplate;

/**

 * function:RestTemplate呼叫REST資源

 * @author hoojo

 * @createDate 2011-6-9 上午11:56:16

 * @file RESTClient.java

 * @package com.hoo.client

 * @project SpringRestWS

 * @blog http://blog.csdn.net/IBM_hoojo

 * @email [email protected]

 * @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請求、postForObject完成post請求、put對應的完成put請求、delete完成delete請求；還有execute可以執行任何請求的方法，需要你設定RequestMethod來指定當前請求型別。

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

引數url是http請求的地址，引數Class是請求響應返回後的資料的型別，最後一個引數是請求中需要設定的引數。

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

如上面的引數是{id}，返回的是一個string型別，設定的引數是id。最後執行該方法會返回一個String型別的結果。

下面建立一個測試類，完成對RESTClient的測試。程式碼如下：

package com.hoo.client;

import org.springframework.beans.factory.annotation.Autowired;

import org.springframework.test.context.ContextConfiguration;

import org.springframework.test.context.junit38.AbstractJUnit38SpringContextTests;

/**

 * function: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.csdn.net/IBM_hoojo

 * @email [email protected]

 * @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"));

    }

}

我們需要在src目錄下新增applicationContext-beans.xml完成對restTemplate的配置。restTemplate需要配置MessageConvert將返回的xml文件進行轉換，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對應的。因為那邊是用xStreamMarshaller進行編組的，所以RestTemplate這邊也需要用它來解組。RestTemplate還指出其他的MarshallingHttpMessageConverter；