jsp+servlet 实现登录功能
现在的框架比较流行，为了更好的理解框架，javaweb的基本开发形式还需要了解。
下面是运用jsp+servlet技术是实现登录。（没有运用数据库，数据操作比较简单，这个例子主要描述开发流程）
project:jspServletLoginTest
项目的目录结构如下：
下面贴上代码：
index.html
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<!-- 该Login页面是一个简单的登录界面 -->
<html >
<head>
<title>Login</title>
<meta http-equiv= "content-type" content = "text/html; charset=UTF-8">
<meta http-equiv= "Content-Language" content = "ch-cn">
</head>
<body >
<!-- Form 用来提取用户填入并提交的信息-->
<form method = "post" name = "frmLogin" action="loginServlet">
<h1 align = "center"> USER LOGIN</h1> <br >
<div align = "center" > User name：
<input type = "text" name = "txtUserName" value = "hym"
size = "20" maxlength = "20" > <br> Password：
<input type = "password" name = "txtPassword" value = "Your password"
size = "20" maxlength = "20" > <br>
<input type = "submit" name = "Submit" value= "submit" onClick = "validateLogin();" >
<input type = "reset" name = "Reset" value = "reset" > <br>
</div>
</form>
<!-- javaScript 函数 validateLogin(),null validate-->
<script language = "javaScript">
function validateLogin( )
{
var sUserName = document. frmLogin. txtUserName. value ;
var sPassword = document. frmLogin. txtPassword. value ;
if( sUserName= = "" )
{
alert( "input user name！" ) ;
return false;
}
if( sPassword= = "" )
{
alert( "input password！" ) ;
return false;
}
}
</script>
</body>
</html>
login_success.jsp
<%@ page language= "java" contentType= "text/html; charset=UTF-8" pageEncoding= "UTF-8" %>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" >
<html>
<head>
<title> My JSP 'login_failure.jsp' starting page </title>
<meta http-equiv= "content-type" content = "text/html; charset=UTF-8">
<meta http-equiv= "pragma" content = "no-cache">
<meta http-equiv= "cache-control" content = "no-cache">
<meta http-equiv= "expires" content = "0">
<meta http-equiv= "keywords" content = "keyword1,keyword2,keyword3">
<meta http-equiv= "description" content = "This is my page">
</head>
<body>
<%
String userName = ( String ) session. getAttribute ( "UserName" ) ;
%>
<div align = center>
<%=userName%>
welcome,logined!
</div>
</body>
</html>
login_failure.jsp
<%@page language= "java" contentType= "text/html; charset=UTF-8" pageEncoding= "UTF-8" %>
<! DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title> My JSP 'login_failure.jsp' starting page </title>
<meta http-equiv= "content-type" content = "text/html; charset=UTF-8">
<meta http-equiv= "pragma" content = "no-cache">
<meta http-equiv= "cache-control" content = "no-cache">
<meta http-equiv= "expires" content = "0">
<meta http-equiv= "keywords" content = "keyword1,keyword2,keyword3">
<meta http-equiv= "description" content = "This is my page">
</head>
<body>
<%
String userName = ( String ) session. getAttribute ( "UserName" ) ;
%>
<div align = center>
<%=userName%>
failure access!
</div>
</body>
</html>
servlet类，表单的数据需要提交到这个类进行处理（页面跳转的控制类），若要深入理解Form的提交和处理原理，则需要深入研究web的HTTP协议
loginServlet.java
package test.login;
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 loginServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
public loginServlet() {
super();
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
}
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
response. setContentType ( "text/html" ) ;
// get username
String sUserName = request.getParameter("txtUserName") ;
// get password
String sPasswd = request.getParameter("txtPassword") ;
//test
System.out.println("username:"+sUserName+"\r\n"+"password:"+sPasswd);
request . getSession( ).setAttribute ( "UserName" , sUserName ) ;
request.getSession().setAttribute("password", sPasswd);
//just compare with hym&123,not do database operation
if(sUserName.equals("hym")&&sPasswd.equals("123"))
{
response. sendRedirect ("login_success.jsp") ;
}
else {
response. sendRedirect ("login_failure.jsp") ;
}
}
}
到目前为止，项目的主要的功能文件已经完成。但是还要在web.xml中注册项目运行的欢迎文件以及servlet的注册。（关于web.xml文件的工作原理有机会在补上了）
web.xml
<?xml version="1.0" encoding="UTF-8"?> <web-app id="WebApp_ID" 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"> <display-name>jspServletLoginTest</display-name> <servlet> <description> </description> <display-name>loginServlet</display-name> <servlet-name>loginServlet</servlet-name> <servlet-class> test.login.loginServlet</servlet-class> </servlet> <servlet-mapping> <servlet-name>loginServlet</servlet-name> <url-pattern>/loginServlet</url-pattern> </servlet-mapping> <!-- 通过如下的设置web project在tomcat服务器上运行的时候，可以首先启动和运行webcontent目录下面 相应的页面，会根据welcome-file的list去检索 --> <welcome-file-list> <welcome-file>index.html</welcome-file> <welcome-file>index.jsp</welcome-file> </welcome-file-list> </web-app>
如此就实现了jsp+servlet实现的用户登录功能。