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; 
 } 

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

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。

• 1. jackson-all-1.9.11.jar 下载地址http://wiki.fasterxml.com/JacksonDownload
• 1. 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); 

 } 
} 

• 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> 

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

本章源码：https://github.com/waylau/RestDemo/tree/master/jersey-demo3-json