如何把错误信息提示在页面上.

Question

alert感觉好些
比如，判断输入不能为空，就用alert...
当然write再有些时候是必须用的

Answer 1

servlet中这样写的：package user;import javax.servlet.*;
import javax.servlet.http.*;
import java.io.*;
import java.util.*;
import java.net.URLEncoder;
import user.*;
import manage.*;
 
//添加用户SERVLET
public class UserManageServlet extends HttpServlet {
String err = "";
 
  private static final String CONTENT_TYPE = "text/html; charset=GBK";
  
  public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    response.setContentType(CONTENT_TYPE);
    
    
   
String action=request.getParameter("action");
 //System.out.println("action value is: "+action);
  if (action.equals("adduser")){
    String getUserName=new String(request.getParameter("UserName").getBytes("iso8859_1"),"gbk");
    String getPassWord=new String(request.getParameter("PassWord").getBytes("iso8859_1"),"gbk");
    String getRePassWord=new String(request.getParameter("RePassWord").getBytes("iso8859_1"),"gbk");
  if(getUserName.equals("")){
   err = URLEncoder.encode("用户名不能为空,请重新输入！");
     response.sendRedirect("/cyvod/manage/adduser.jsp?err="+err);
  }else
  if(getPassWord.equals("")){
   err = URLEncoder.encode("密码不能为空,请重新输入！");
     response.sendRedirect("/cyvod/manage/adduser.jsp?err="+err);
  }else
  if(!getPassWord.equals(getRePassWord)){
      err = URLEncoder.encode("两次密码输入不同,请重新输入！");
     response.sendRedirect("/cyvod/manage/adduser.jsp?err="+err);
   }else
   {
      UserManage add=new UserManage();
      add.UserName=getUserName;
      add.PassWord=getPassWord;
      //add.RePassWord=getPassWord;
      add.AddUser();
      
    err = URLEncoder.encode("提交成功！");
    response.sendRedirect("/cyvod/manage/adduser.jsp?err="+err);
                            // /mes/msgboard.jsp这么写是因为这个文件在服务器的根目录下
   
    }
  }else
   if (action.equals("deluser")){
     String deluser=new String(request.getParameter("v1").getBytes("iso8859_1"),"gbk");
       //System.out.print(getUserNameSel);
       if(deluser.equals("")){
     err = URLEncoder.encode("用户名为空,怎么查询啊？请重新输入！");
          response.sendRedirect("/cyvod/manage/info.jsp?err="+err);
         }else
         {
            UserManage del=new UserManage();
           del.getdeluser=deluser;
           del.DelUser();
            err = URLEncoder.encode("删除成功！");
           response.sendRedirect("/cyvod/manage/info.jsp?err="+err);
          }
     
      }   
}
}
jsp中这样写：
<%
if(request.getParameter("err")!=null)
{
String err=URLDecoder.decode(new String(request.getParameter("err").getBytes("iso8859_1"),"gbk"));
out.print(err);
}
%>