json-lib-2.3-jdk15.jar 
commons-beanutils-1.7.0.jar 
commons-httpclient-3.1.jar 
commons-lang-2.3.jar 
commons-logging-1.0.4.jar 
commons-collections-3.1.jar 
ezmorph-1.0.3.jar 
这些包可以从一下地方下载: 
http://commons.apache.org/index.html 
http://json-lib.sourceforge.net/ 
http://ezmorph.sourceforge.net/ 
http://www.docjar.com/ 
如果不关联这些包,则会出现以下错误: 
java.lang.NoClassDefFoundError: net/sf/ezmorph/Morpher 
java.lang.NoClassDefFoundError: org/apache/commons/collections/map/ListOrderedMap 
java.lang.NoClassDefFoundError: org/apache/commons/beanutils/DynaBean 
java.lang.NoClassDefFoundError: org/apache/commons/codec/DecoderException 
java.lang.NoClassDefFoundError: org/apache/commons/lang/exception/NestableRuntimeException 
java.lang.NoClassDefFoundError: org/apache/commons/logging/LogFactory 
package com.json;          
         
public class User {          
    String username;          
    String password;          
    public String getUsername() {          
        return username;          
    }          
    public void setUsername(String username) {          
        this.username = username;          
    }          
    public String getPassword() {          
        return password;          
    }          
    public void setPassword(String password) {          
        this.password = password;          
    }          
              
}   
package com.json;          
         
import java.io.IOException;          
import java.io.PrintWriter;          
import java.util.ArrayList;          
import java.util.List;          
         
import javax.servlet.ServletException;          
import javax.servlet.http.HttpServlet;          
import javax.servlet.http.HttpServletRequest;          
import javax.servlet.http.HttpServletResponse;          
         
import net.sf.json.JSONArray;          
         
public class TestJson extends HttpServlet {          
         
    public void doGet(HttpServletRequest request, HttpServletResponse response)          
            throws ServletException, IOException {          
           doPost(request,response);          
    }          
    public void doPost(HttpServletRequest request, HttpServletResponse response)          
            throws ServletException, IOException {          
         
        response.setContentType("text/html");             
    String str= request.getParameter("name");//得到ajax传递过来的paramater          
        System.out.print(str);          
        PrintWriter out = response.getWriter();          
        List list = new ArrayList();//传递List          
                  Map m=new HashMap();//传递Map              
        User u1=new User();          
        u1.setUsername("zah");          
        u1.setPassword("123");          
        User u2=new User();          
        u2.setUsername("ztf");          
        u2.setPassword("456");            
        list.add(u1); //添加User对象                
         list.add(u2);     //添加User对象            
                
          m.put("u1", u1);          
         m.put("u2", u2);             
         
   JSONArray jsonArray2 = JSONArray.fromObject( list );          
       //把java数组转化成转化成json对象           
   JSONObject jo=JSONObject.fromObject(m);//转化Map对象          
        out.print(jsonArray2);//返给ajax请求          
       out.print(jo);//返给ajax请求          
    }          
}   
<script type="text/javascript" src="js/jquery.js"></script>          
 <script type="text/javascript">          
     function test(){          
         $.ajax({           
                type:"POST", //请求方式          
                url:"testjson", //请求路径          
                cache: false,             
                data:"name=zah",  //传参          
                dataType: ‘json‘,   //返回值类型          
               success:function(json){                
                    alert(json[0].username+" " json[0].password);    //弹出返回过来的List对象          
                   }          
                });          
      }          
</script>          
  </head>          
  <body>          
    <input type="button" name="b" value="测试" onclick=test()>          
  </body>
原文:http://www.cnblogs.com/hkxd-1/p/4854561.html