用Jersey构建RESTful服务-JAVA对象转成XML/Json输出

1、XML数据类型输出：

一、 总体说明

XML和JSON 是最为常用的数据交换格式。本例子演示如何将java对象，转成XML输出。

二、流程

1.在上文的例子中，创建一个包“com.waylau.rest.bean”

2.在该包下创建一个JAVA类"User"

package com.waylau.rest.bean;
import javax.xml.bind.annotation.XmlRootElement;
/*
 * 用户 bean
 * @author waylau.com
 * 2014-3-17
 */
@XmlRootElement
public class User {

    private String userId;
    private String userName;
    private String age;

    public User() {};

    public User(String userId, String userName, String age) {
        this.userId = userId;
        this.userName = userName;
        this.age = age;
    }
    public String getUserId() {
        return userId;
    }
    public void setUserId(String userId) {
        this.userId = userId;
    }
    public String getUserName() {
        return userName;
    }
    public void setUserName(String userName) {
        this.userName = userName;
    }
    public String getAge() {
        return age;
    }
    public void setAge(String age) {
        this.age = age;
    }
}

package com.waylau.rest.bean;
import javax.xml.bind.annotation.XmlRootElement;
/*
 * 用户 bean
 * @author waylau.com
 * 2014-3-17
 */
@XmlRootElement
public class User {
	
	private String userId;
	private String userName;
	private String age;
	
	public User() {};
	
	public User(String userId, String userName, String age) {
		this.userId = userId;
		this.userName = userName;
		this.age = age;
	}
	public String getUserId() {
		return userId;
	}
	public void setUserId(String userId) {
		this.userId = userId;
	}
	public String getUserName() {
		return userName;
	}
	public void setUserName(String userName) {
		this.userName = userName;
	}
	public String getAge() {
		return age;
	}
	public void setAge(String age) {
		this.age = age;
	}
}

注意：该类上面增加了一个注解“@XmlRootElement”，在将该类转化成XML时，说明这个是XML的根节点。

3.在“com.waylau.rest.resources”中，增加资源“UserResource“，代码如下：

package com.waylau.rest.resources;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

import javax.ws.rs.Path;
import javax.ws.rs.Produces;
import javax.ws.rs.PathParam;
import javax.ws.rs.core.MediaType;
import javax.ws.rs.DELETE;
import javax.ws.rs.GET;
import javax.ws.rs.POST;
import javax.ws.rs.PUT;

import com.waylau.rest.bean.User;

@Path("/users")
public class UserResource {
    private static Map<String,User> userMap = new HashMap<String,User>();//存储用户
     /**
     * 查询所有
     * @return
     */
    @GET
    @Produces(MediaType.APPLICATION_XML)
    public List<User> getAllUsers(){
        List<User> users = new ArrayList<User>();
        User u1 = new User("001","WayLau","26");
        User u2 = new User("002","King","23");
        User u3 = new User("003","Susan","21");

        userMap.put(u1.getUserId(), u1);
        userMap.put(u2.getUserId(), u2);
        userMap.put(u3.getUserId(), u3);

        users.addAll( userMap.values() );
        return users;
    }

    @GET
    @Path("/getUserXml")
    @Produces(MediaType.APPLICATION_XML)
    public User getUserXml() {
     User user  = new User();
     user.setAge("21");
     user.setUserId("004");
     user.setUserName("Amand");
     return user;
    }



}

其中MediaType.APPLICATION_XML 说明了是以XML形式输出

在浏览器输入http://localhost:8089/RestDemo/rest/users/getUserXml，输出单个对象

在浏览器输入 http://localhost:8089/RestDemo/rest/users  输出对象的集合

2、数据输出为JSON类型：

一、 总体说明

XML和JSON 是最为常用的数据交换格式。本例子演示如何将java对象，转成JSON输出。

二、流程

1.在上文项目中，

在“com.waylau.rest.resources.UserResource“中增加代码，代码如下：

@GET
@Path("/getUserJson")
@Produces(MediaType.APPLICATION_JSON)
public User getUserJson() {
 User user  = new User();
 user.setAge("27");
 user.setUserId("005");
 user.setUserName("Fmand");
 return user;
}

    @GET  
    @Path("/getUserJson")  
    @Produces(MediaType.APPLICATION_JSON)  
    public User getUserJson() {  
     User user  = new User();  
     user.setAge("27");  
     user.setUserId("005");  
     user.setUserName("Fmand");  
     return user;  
    } 

MediaType.APPLICATION_JSON 说明输出的是JSON格式

2,运行项目，浏览器输入http://localhost:8089/RestDemo/rest/users/getUserJson

期望获取到json的数据，此时，项目报错

org.glassfish.jersey.message.internal.MessageBodyProviderNotFoundException: MessageBodyWriter not found for media type=application/json, type=class com.waylau.rest.bean.User, genericType=class com.waylau.rest.bean.User.
    at org.glassfish.jersey.message.internal.WriterInterceptorExecutor$TerminalWriterInterceptor.aroundWriteTo(WriterInterceptorExecutor.java:247)
    at org.glassfish.jersey.message.internal.WriterInterceptorExecutor.proceed(WriterInterceptorExecutor.java:162)
    at org.glassfish.jersey.filter.LoggingFilter.aroundWriteTo(LoggingFilter.java:293)
    at org.glassfish.jersey.message.internal.WriterInterceptorExecutor.proceed(WriterInterceptorExecutor.java:162)
    at org.glassfish.jersey.server.internal.JsonWithPaddingInterceptor.aroundWriteTo(JsonWithPaddingInterceptor.java:103)
    at org.glassfish.jersey.message.internal.WriterInterceptorExecutor.proceed(WriterInterceptorExecutor.java:162)
    at org.glassfish.jersey.server.internal.MappableExceptionWrapperInterceptor.aroundWriteTo(MappableExceptionWrapperInterceptor.java:88)
    at org.glassfish.jersey.message.internal.WriterInterceptorExecutor.proceed(WriterInterceptorExecutor.java:162)
    at org.glassfish.jersey.message.internal.MessageBodyFactory.writeTo(MessageBodyFactory.java:1154)
    at org.glassfish.jersey.server.ServerRuntime$Responder.writeResponse(ServerRuntime.java:571)
    at org.glassfish.jersey.server.ServerRuntime$Responder.processResponse(ServerRuntime.java:378)
    at org.glassfish.jersey.server.ServerRuntime$Responder.process(ServerRuntime.java:368)
    at org.glassfish.jersey.server.ServerRuntime$1.run(ServerRuntime.java:262)

org.glassfish.jersey.message.internal.MessageBodyProviderNotFoundException: MessageBodyWriter not found for media type=application/json, type=class com.waylau.rest.bean.User, genericType=class com.waylau.rest.bean.User.
	at org.glassfish.jersey.message.internal.WriterInterceptorExecutor$TerminalWriterInterceptor.aroundWriteTo(WriterInterceptorExecutor.java:247)
	at org.glassfish.jersey.message.internal.WriterInterceptorExecutor.proceed(WriterInterceptorExecutor.java:162)
	at org.glassfish.jersey.filter.LoggingFilter.aroundWriteTo(LoggingFilter.java:293)
	at org.glassfish.jersey.message.internal.WriterInterceptorExecutor.proceed(WriterInterceptorExecutor.java:162)
	at org.glassfish.jersey.server.internal.JsonWithPaddingInterceptor.aroundWriteTo(JsonWithPaddingInterceptor.java:103)
	at org.glassfish.jersey.message.internal.WriterInterceptorExecutor.proceed(WriterInterceptorExecutor.java:162)
	at org.glassfish.jersey.server.internal.MappableExceptionWrapperInterceptor.aroundWriteTo(MappableExceptionWrapperInterceptor.java:88)
	at org.glassfish.jersey.message.internal.WriterInterceptorExecutor.proceed(WriterInterceptorExecutor.java:162)
	at org.glassfish.jersey.message.internal.MessageBodyFactory.writeTo(MessageBodyFactory.java:1154)
	at org.glassfish.jersey.server.ServerRuntime$Responder.writeResponse(ServerRuntime.java:571)
	at org.glassfish.jersey.server.ServerRuntime$Responder.processResponse(ServerRuntime.java:378)
	at org.glassfish.jersey.server.ServerRuntime$Responder.process(ServerRuntime.java:368)
	at org.glassfish.jersey.server.ServerRuntime$1.run(ServerRuntime.java:262)

此时，需要获取json转换包的支持 。

可以由多种方式实现：MOXy、JSON-P、Jackson、Jettison等，本例为Jackson。

3. jackson-all-1.9.11.jar 下载地址http://wiki.fasterxml.com/JacksonDownload

4. 项目中引入jackson-all-1.9.11.jar

5.在“com.waylau.rest”目录下创建RestApplication.java

package com.waylau.rest;

import org.codehaus.jackson.jaxrs.JacksonJsonProvider;
import org.glassfish.jersey.filter.LoggingFilter;
import org.glassfish.jersey.server.ResourceConfig;

/**
 * 应用
 * @author waylau.com
 * 2014-3-18
 */
public class RestApplication extends ResourceConfig {
    public RestApplication() {

     //服务类所在的包路径
     packages("com.waylau.rest.resources");
     //注册JSON转换器
     register(JacksonJsonProvider.class);

    }
}

package com.waylau.rest;

import org.codehaus.jackson.jaxrs.JacksonJsonProvider;
import org.glassfish.jersey.filter.LoggingFilter;
import org.glassfish.jersey.server.ResourceConfig;
 
/**
 * 应用
 * @author waylau.com
 * 2014-3-18
 */
public class RestApplication extends ResourceConfig {
    public RestApplication() {
 
     //服务类所在的包路径
     packages("com.waylau.rest.resources");
     //注册JSON转换器
     register(JacksonJsonProvider.class);
 
    }
}

6.修改web.xml，初始化从RestApplicaton进入应用，如下：

<servlet>
     <servlet-name>Way REST Service</servlet-name>
     <servlet-class>org.glassfish.jersey.servlet.ServletContainer</servlet-class>
      <init-param>
           <param-name>javax.ws.rs.Application</param-name>
           <param-value>com.waylau.rest.RestApplication</param-value>
       </init-param>

    <load-on-startup>1</load-on-startup>
  </servlet>

  <servlet-mapping>
    <servlet-name>Way REST Service</servlet-name>
    <url-pattern>/rest/*</url-pattern>
  </servlet-mapping>

<servlet>  
     <servlet-name>Way REST Service</servlet-name>
	 <servlet-class>org.glassfish.jersey.servlet.ServletContainer</servlet-class>
	  <init-param>
	       <param-name>javax.ws.rs.Application</param-name>
	       <param-value>com.waylau.rest.RestApplication</param-value>
	   </init-param>
	 
    <load-on-startup>1</load-on-startup>
  </servlet>
  
  <servlet-mapping>
    <servlet-name>Way REST Service</servlet-name>
    <url-pattern>/rest/*</url-pattern>
  </servlet-mapping>

7.运行项目，再次访问http://localhost:8089/RestDemo/rest/users/getUserJson
即可输出JSON文本