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！

spring配置文件

<?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>

 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。 

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.csdn.net/IBM_hoojo * @email [e-mail] * @version 1.0 */@RequestMapping("/restful")@Controllerpublic 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。

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.csdn.net/IBM_hoojo * @email [e-mail] * @version 1.0 */@Componentpublic 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.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；