spring RestTemplate用法详解

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！

 

Blog：http://blog.csdn.net/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">

    <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、 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;

/**

 * 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 [e-mail]

 * @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;

/**

 * function: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.csdn.net/IBM_hoojo

 * @email [e-mail]

 * @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 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;

/**

 * 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 [e-mail]

 * @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；