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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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