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。

jackson-all-1.9.11.jar 下载地址http://wiki.fasterxml.com/JacksonDownload
import org.codehaus.jackson.jaxrs.JacksonJsonProvider;  
import org.glassfish.jersey.filter.LoggingFilter;  
import org.glassfish.jersey.server.ResourceConfig;  
 * @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
 Code licensed under MIT,documentation under CC BY-NC-SA 3.0 CN
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