## 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)
~~~
![](https://box.kancloud.cn/2016-02-24_56cd25fd2334d.png)
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:
~~~
<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](http://localhost:8089/RestDemo/rest/users/getUserJson)
即可输出JSON文本
![](https://box.kancloud.cn/2016-02-24_56cd25fd43ca9.png)