通过ajax从jsp页面传输数据到web层，并从web层返回数据给jsp页面

jsp中ajax代码：
 1            $.ajax({
 2               var id = $("#studentid").val();//获取标签中的学生id
 3               url:‘${pageContext.request.contextPath}/student/stu_delStudent.action?studentid=‘+id,
 4               data:‘‘,
 5               type:‘POST‘,
 6               dataType:‘json‘,
 7               async:false,
 8               success:function(data){
 9                   alert(data.message);
10               }
11               
12           }); 

action中的代码：
1 public class StudentAction extends ActionSupport{
 2     private Student student;
 3     public Student getStudent() {
 4         return student;
 5     }
 6     public void setStudent(Student student) {
 7         this.student = student;
 8     }
 9 
10     @Resource
11     private StudentService studentService;
12     
13     public String delStudent() throws Exception{
14         //接收请求数据
15         int studentid = ServletActionContext.getRequest().getParameter("studentid");
16         studentSerivce.delByStudentId(studentid);
17         //创建一个JSON对象
18         JSONObject json = new JSONObject();
19         json.put(“message",删除成功");//将返回信息保存在JSON对象中
20         HttpServletResponse response = ServletActionContext.getResponse();
21         //设置响应编码格式，防止乱码
22         response.setContentType("text/html;charset=UTF-8");
23         //将数据以json格式响应给ajax
24         response.getWriter().write(json.toString());
25         
26         return null;
27     }
28 }