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场景：用Jersey构建RESTful服务3-JAVA对象转成JSON输出
用Jersey构建RESTful服务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
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
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
即可输出JSON文本
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