3–JAVA对象转成JSON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](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) ~~~  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](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); } } ~~~ 6.修改web.xml，初始化从RestApplicaton进入应用，如下： ~~~ Way REST Service org.glassfish.jersey.servlet.ServletContainer javax.ws.rs.Application com.waylau.rest.RestApplication 1 Way REST Service /rest/* ~~~ 7.运行项目，再次访问[http://localhost:8089/RestDemo/rest/users/getUserJson](http://localhost:8089/RestDemo/rest/users/getUserJson) 即可输出JSON文本