login.html:
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Title</title>
</head>
<body>
<form name="req" action="/LoginServlet" method="get">
用户名:
<input name="username" type="text"/><br>
密码：
<input name="password" type="password"/><br>
<input type="submit" value="提交" id="bt"/>
</form>
</body>
</html>
web.xml:
<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd"
version="4.0">
<servlet>
<servlet-name>LoginServlet</servlet-name>
<servlet-class>com.huizhi.bean.LoginServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>LoginServlet</servlet-name>
<url-pattern>/LoginServlet</url-pattern>
</servlet-mapping>
<servlet>
<servlet-name>IndexServlet</servlet-name>
<servlet-class>com.huizhi.bean.IndexServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>IndexServlet</servlet-name>
<url-pattern>/IndexServlet</url-pattern>
</servlet-mapping>
<servlet>
<servlet-name>LogoutServlet</servlet-name>
<servlet-class>com.huizhi.bean.LogoutServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>LogoutServlet</servlet-name>
<url-pattern>/LogoutServlet</url-pattern>
</servlet-mapping>
</web-app>User.java:
package com.huizhi.bean;
public class User {
private String username;
private String password;
//set get略
}LoginServlet.java:
package com.huizhi.bean;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.io.PrintWriter;
public class LoginServlet extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws IOException{
response.setContentType("text/html;charset=utf-8");
String username=request.getParameter("username");
String password=request.getParameter("password");
PrintWriter out=response.getWriter();
if(username.equals("leilei")&&password.equals("123")){
// if(("leilei").equals(username)&&("123").equals("password")){
User user=new User();
user.setUsername(username);
user.setPassword(password);
request.getSession().setAttribute("user",user);
response.sendRedirect("/IndexServlet");
}else{
out.write("用户名或密码错误，登录失败");
/*
write()：仅支持输出字符类型数据，字符、字符数组、字符串等
print()：可以将各种类型（包括Object）的数据通过默认编码转
换成bytes字节形式，这些字节都通过write(int c)方法被输出
JspWriter类型的out对象使用print方法和write方法都可以输出字符串，
但是，如果字符串对象的值为null时，print方法将输出内容为“null”的字符串，
而write方法则是抛出NullPointerException异常。
*/
}
}
}IndexServlet.java:
package com.huizhi.bean;
import javax.servlet.http.*;
import java.io.IOException;
public class IndexServlet extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws IOException {
response.setContentType("text/html;charset=utf-8");
HttpSession session=request.getSession();
User user=(User)session.getAttribute("user");
if(user==null){
response.getWriter().print(
"您还没有登录,请<a href='/login.html'>登录</a>"
);
}else{
response.getWriter().print(
"您已登录，欢迎你，"+user.getUsername()+"!"
);
response.getWriter().print(
"<a href='/LogoutServlet'>退出</a>"
);
//创建Cookie存放Session的标识号
Cookie cookie=new Cookie("leilei",session.getId());
cookie.setMaxAge(60*30);
cookie.setPath("/");
response.addCookie(cookie);
}
}
public void doPost(HttpServletResponse response,HttpServletRequest request)
throws IOException{
doGet(request,response);
}
}LogoutServlet.java:
package com.huizhi.bean;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
public class LogoutServlet extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
request.getSession().removeAttribute("user");
response.sendRedirect("/IndexServlet");
}
public void doPost(HttpServletResponse response,HttpServletRequest request)
throws ServletException,IOException{
doGet(request,response);
}
}
