用Jersey构建RESTful服务4--通过jersey-client客户端调用Jersey的Web服务模拟CURD

一、总体说明

通过jersey-client接口，创建客户端程序，来调用Jersey实现的RESTful服务，实现增、删、改、查等操作。服务端主要是通过内存的方式，来模拟用户的增加、删除、修改、查询等操作。

二、创建服务端

在上文项目中，在“com.waylau.rest.resources.UserResource“中修改代码，首先创建一个HashMap，用来保存添加的用户
```
private static Map<String,User> userMap  = new HashMap<String,User>();
```

创建增、删、改、查用户资源等操作

 /**
     * 增加
     * @param user
     */  
    @POST  
    @Consumes({MediaType.APPLICATION_XML, MediaType.APPLICATION_JSON})  
    public void createStudent(User user) {  
        userMap.put(user.getUserId(), user );  
    }  

    /**
     * 删除
     * @param id
     */  
    @DELETE  
    @Path("{id}")  
    public void deleteStudent(@PathParam("id")String id){  
        userMap.remove(id);  
    }  

    /**
     * 修改
     * @param user
     */  
    @PUT  
    @Consumes(MediaType.APPLICATION_XML)  
    public void updateStudent(User user){  
        userMap.put(user.getUserId(), user );  
    }  

    /**
     * 根据id查询
     * @param id
     * @return
     */  
    @GET  
    @Path("{id}")  
    @Produces({MediaType.APPLICATION_XML, MediaType.APPLICATION_JSON})  
    public User getUserById(@PathParam("id") String id){  
        User u = userMap.get(id);  
        return u;  
    }  

    /**
     * 查询所有
     * @return
     */  
    @GET  
    @Produces({MediaType.APPLICATION_XML, MediaType.APPLICATION_JSON})  
    public List<User> getAllUsers(){       
        List<User> users = new ArrayList<User>();     
        users.addAll( userMap.values() );    
        return users;  
    }

三、创建客户端程序

创建包“com.waylau.rest.client”，在包下建一个UserClient.java，代码如下：

 package com.waylau.rest.client;  

    import javax.ws.rs.client.Client;  
    import javax.ws.rs.client.ClientBuilder;  
    import javax.ws.rs.client.Entity;  
    import javax.ws.rs.client.WebTarget;  
    import javax.ws.rs.core.MediaType;  
    import javax.ws.rs.core.Response;  

    import org.codehaus.jackson.jaxrs.JacksonJsonProvider;  

    import com.waylau.rest.bean.User;  

    /**
     * 用户客户端，用来测试资源
     * @author waylau.com
     * 2014-3-18
     */  
    public class UserClient {  

        private static String serverUri = "http://localhost:8089/RestDemo/rest";  
        /**
         * @param args
         */  
        public static void main(String[] args) {  
            addUser();  
            getAllUsers();  
            updateUser();  
            getUserById();  
            getAllUsers();  
            delUser();  
            getAllUsers();  

        }  
        /**
         * 添加用户
         */  
         private static void addUser() {  
             System.out.println("****增加用户addUser****");  
             User user = new User("006","Susan","21");    
             Client client = ClientBuilder.newClient();  
             WebTarget target = client.target(serverUri + "/users");  
             Response response = target.request().buildPost(Entity.entity(user, MediaType.APPLICATION_XML)).invoke();  
             response.close();  
        }  

        /**
         * 删除用户
         */  
         private static void delUser() {  
             System.out.println("****删除用户****");  
             Client client = ClientBuilder.newClient();  
             WebTarget target = client.target(serverUri + "/users/006");  
             Response response = target.request().delete();  
             response.close();  
        }  

        /**
         * 修改用户
         */  
         private static void updateUser() {  
             System.out.println("****修改用户updateUser****");  
             User user = new User("006","Susan","33");    
             Client client = ClientBuilder.newClient();  
             WebTarget target = client.target(serverUri + "/users");  
             Response response = target.request().buildPut( Entity.entity(user, MediaType.APPLICATION_XML)).invoke();  
             response.close();  
        }  
        /**
         * 根据id查询用户
         */  
         private static void getUserById() {  
             System.out.println("****根据id查询用户****");  
             Client client = ClientBuilder.newClient().register(JacksonJsonProvider.class);// 注册json 支持
             WebTarget target = client.target(serverUri + "/users/006");  
             Response response = target.request().get();  
             User user = response.readEntity(User.class);  
             System.out.println(user.getUserId() + user.getUserName()  +  user.getAge());  
             response.close();  
        }  
        /**
         * 查询所有用户
         */  
         private static void getAllUsers() {  
             System.out.println("****查询所有getAllUsers****");  

             Client client = ClientBuilder.newClient();  

             WebTarget target = client.target(serverUri + "/users");  
             Response response = target.request().get();  
             String value = response.readEntity(String.class);  
             System.out.println(value);  
             response.close();  //关闭连接
         }  

    }

四、运行

启动服务端项目，运行客户端程序UserClient，控制台输出如下

****增加用户addUser****  
****查询所有getAllUsers****  
[{"userId":"006","userName":"Susan","age":"21"}]  
****修改用户updateUser****  
****根据id查询用户****  
006Susan33  
****查询所有getAllUsers****  
[{"userId":"006","userName":"Susan","age":"33"}]  
****删除用户****  
****查询所有getAllUsers****  
[]

五、总结

客户端如果需要进行JSON转换，需要进行JSON注册

Client client = ClientBuilder.newClient().register(JacksonJsonProvider.class);

WebTarget 指明了要请求的资源的地址
target.request(). 后面跟的是请求的方法:POST，GET，PUT或DELETE

本章源码：https://github.com/waylau/RestDemo/tree/master/jersey-demo4-client-curd