我用了以个button,用来点击检查用户名是否存在,但是不知道代码怎么写,求完整代码实例.
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<%@ page language="java" pageEncoding="GBK"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>My JSP 'MyJsp1.jsp' starting page</title>
</head>
<body>
<form action="/JD/check" method="POST">
用户名:<input type="text" id="name" name="name"><input type="submit" value="[检查用户名重否]"><em><%=request.getAttribute("msg")==null?"":request.getAttribute("msg")%></em>
</form>
</body>
</html>package csdn;
import java.io.IOException;import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;public class CheckExist extends HttpServlet { /**
* Destruction of the servlet. <br>
*/
public void destroy() {
super.destroy(); // Just puts "destroy" string in log
// Put your code here
} /**
* Initialization of the servlet. <br>
*
* @throws ServletException if an error occurs
*/
public void init() throws ServletException {
// Put your code here
}
protected void service(HttpServletRequest req, HttpServletResponse resp)
throws ServletException, IOException {
String msg = "";
String name = req.getParameter("name");
if(name==null || name.trim().length()==0){
msg = "非法字符串,空字符串";
}else{
//去数据库查询
//如果查到
if(true){
msg = "用户名已存在!";
}else{
msg = "用户名可用!";
}
}
req.setAttribute("msg",msg);
req.getRequestDispatcher("/MyJsp1.jsp").forward(req, resp);
}}<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.4"
xmlns="http://java.sun.com/xml/ns/j2ee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee
http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd">
<servlet>
<servlet-name>DataTest</servlet-name>
<servlet-class>csdn.DataTest</servlet-class>
</servlet>
<servlet>
<servlet-name>CheckExist</servlet-name>
<servlet-class>csdn.CheckExist</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>DataTest</servlet-name>
<url-pattern>/DataTest</url-pattern>
</servlet-mapping>
<servlet-mapping>
<servlet-name>CheckExist</servlet-name>
<url-pattern>/check</url-pattern>
</servlet-mapping>
<welcome-file-list>
<welcome-file>index.jsp</welcome-file>
</welcome-file-list>
</web-app>