無廢話Jersey構建RESTful服務之WebService系統教程 --3 [JAVA對象轉成JSON輸出]

一、 總體說明

XML和JSON 是最為常用的數據交換格式。本例子演示如何將JAVA對象，轉換成JSON輸出。

 

二、流程

1.在上文項目中，

在“cn.itrush.rest.resources.UserResource“中增加代碼，代碼如下：

package cn.itrush.rest.resources;  
  
import java.util.ArrayList;  
import java.util.HashMap;  
import java.util.List;  
import java.util.Map;  
  
import javax.ws.rs.Path;  
import javax.ws.rs.Produces;  
import javax.ws.rs.PathParam;  
import javax.ws.rs.core.MediaType;  
import javax.ws.rs.DELETE;  
import javax.ws.rs.GET;  
import javax.ws.rs.POST;  
import javax.ws.rs.PUT;  
  
import cn.itrush.rest.bean.User;

/** 
 * 回嘉
 * @author huiqinbo.cn
 * 2016-8-24
 */  

@Path("/users")  
public class UserResource {  
    private static Map<String,User> userMap = new HashMap<String,User>();//�洢�û�  
     
    /** 
     * 返回多節點XML格式文件
     * @return 
     */
    @GET  
    @Produces(MediaType.APPLICATION_XML)  
    public List<User> getAllUsers(){       
        List<User> users = new ArrayList<User>();  
        User u1 = new User("001","HuiJia","26");  
        User u2 = new User("002","Andy","23");  
        User u3 = new User("003","BoWen","21");  
          
        userMap.put(u1.getUserId(), u1);  
        userMap.put(u2.getUserId(), u2);  
        userMap.put(u3.getUserId(), u3);  
          
        users.addAll( userMap.values() );  
        return users;  
    }  
    
    
    /** 
     * 返回單節點XML格式文件
     * @return 
     */
    @GET  
    @Path("/getUserXml")  
    @Produces(MediaType.APPLICATION_XML)  
    public User getUserXml() {  
     User user  = new User();  
     user.setAge("21");  
     user.setUserId("004");  
     user.setUserName("回嘉");  
     return user;  
    }  
    
    /** 
     * 返回單節點Json格式文件
     * @return 
     */
69     @GET
70     @Path("/getUserJson")
71     @Produces(MediaType.APPLICATION_JSON)
72     public User getUserJson(){
73         User user = new User();
74         user.setAge("30");
75         user.setUserId("2");
76         user.setUserName("回嘉");
77         return user;
78  }  
}  

注：紅色部分為新增J的AVA對象返回JSON 的代碼，其它部分是第2節的內容

注：MediaType.APPLICATION_JSON 說明輸出的是JSON格式

 

2,運行項目，瀏覽器輸入http://localhost:8080/RestDemo/rest/users/getUserJson

期望獲取到json的數據，此時，項目報錯

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) 

 

瀏覽器報錯頁面顯示：

 

 

此時，需要獲取json轉換包的支持 。

可以由多種方式實現：MOXy、JSON-P、Jackson、Jettison等，本例為Jackson。

3. jackson-all-1.9.11.jar 下載地址我是從CSND(http://download.csdn.net/detail/wind520/5674963)上面下載一個。

4. 項目中引入jackson-all-1.9.11.jar   

注：將jackson-all-1.9.11.jar先放入項目工程的文件夾里，再刷新項目；如果直接放入項目內會報錯

 

5.在“cn.itrush.rest”目錄下創建RestApplication.java

 

package cn.itrush.rest;  
  
import org.codehaus.jackson.jaxrs.JacksonJsonProvider;  
import org.glassfish.jersey.filter.LoggingFilter;  
import org.glassfish.jersey.server.ResourceConfig;  
   
/** 
 * 回嘉
 * @author huiqinbo.cn
 * 2016-8-24
 */  
public class RestApplication extends ResourceConfig {  
    public RestApplication() {  
   
     //服務類所在的包路徑
     packages("cn.itrush.rest.resources");  
     //注冊JSON轉換器  
     register(JacksonJsonProvider.class);  
   
    }  
}  

 

 6.修改web.xml，初始化從RestApplicaton進入應用，如下：

 

<?xml version="1.0" encoding="UTF-8"?>
<web-app id="WebApp_ID">
    <display-name>RestDemo</display-name>
    <welcome-file-list>
        <welcome-file>index.html</welcome-file>
        <welcome-file>index.htm</welcome-file>
        <welcome-file>index.jsp</welcome-file>
        <welcome-file>default.html</welcome-file>
        <welcome-file>default.htm</welcome-file>
        <welcome-file>default.jsp</welcome-file>
    </welcome-file-list>
    
    <servlet>
        <servlet-name>Way REST Service</servlet-name>  
     <servlet-class>org.glassfish.jersey.servlet.ServletContainer</servlet-class>  
          <init-param>
                <!-- <param-name>jersey.config.server.provider.packages</param-name>  
                <param-value>cn.itrush.rest.resources</param-value> -->
                <param-name>javax.ws.rs.Application</param-name>
                   <param-value>cn.itrush.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>
    
      
    
</web-app>

注：注釋部分是轉換成XML時用的。下面是轉換成JSON時用的。

 

7.運行項目，再次訪問http://localhost:8080/RestDemo/rest/users/getUserJson
即可輸出JSON文本

 

JSON格式里有亂碼問題，以后再解決。