struts2的java文件中不能直接弹出script对话框

 1 public class Login extends ActionSupport implements SessionAware,ServletResponseAware
 2 {
 3         
 4     private HttpServletResponse response = null;
 5 　　　　....
 6     public void setServletResponse(HttpServletResponse response) {
 7         // TODO Auto-generated method stub
 8         this.response = response;
 9     }
10 
11     public String execute()
12     {
13         Person person = new Person();
14         PersonDAO personDAO = new PersonDAO();
15         if(personDAO.findById(id)==null)
16         {
17             System.out.println("用户不存在");
18             try {
19                 response.setContentType("text/html; charset=UTF-8");
20                 response.setCharacterEncoding("UTF-8");        //防止乱码；
21                 PrintWriter out = response.getWriter();
22                 out.print("<Script>alert('用户不存在!')</Script>");
23                 out.flush();
24                 out.close();
25             }
26             catch (IOException e) {
27                 // TODO Auto-generated catch block
28                 e.printStackTrace();
29             }
30         }
31     ....
32     } 
33 }
34