JavaWeb session——模拟实现用户登录（教材学习笔记）

首先我们要了解用户登录的整个流程，

1、从浏览器访问网站首页IndexServlet

2、判断用后是否登录

3、若以登录则显示用户信息

4、若未登录，进图登录界面login.html;

4.1、处理用户登录信息（LoginServlet）

4.2、判断用户名和密码是否正确

4.3、若正确则显示用户信息

4.4、若不正确则提示用户名或密码错误

5、若用户退出，则进入LogoutServlet界面

下面我们通过上面的流程来建立代码，

一、创建封装用户信息类

创建一个名为web-chapter05的web项目，并在其中创建cn.itcast.chapter05.session.example02的包，并在包中创建一个User类

代码如下：

package cn.itcast.chapter05.session.example02;

public class User {
    private String username;
    private String password;
	public String getUsername() {
		return username;
	}
	public void setUsername(String username) {
		this.username = username;
	}
	public String getPassword() {
		return password;
	}
	public void setPassword(String password) {
		this.password = password;
	}
    
}

二、创建IndexServlet类

在cn.itcast.chapter05.session.example02的包中创建IndexServlet类，该类是显示网站的首页

package cn.itcast.chapter05.session.example02;

import java.io.*;
import javax.servlet.ServletException;
import javax.servlet.http.*;

public class IndexServlet extends HttpServlet {
	private static final long serialVersionUID = 1L;
	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		//解决乱码问题
		response.setContentType("text/html;charset=utf-8");
		//创建或者获取保存用户信息的session对象
		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='/web-chapter05/login.html'>登录</a>");
		}else {
			response.getWriter().print("您已登录，欢迎你，"+ user.getUsername()+"！");
			response.getWriter().print("<a href='/web-chapter05/LogoutServlet'>退出</a>");
			//创建cookie存放session的标识号
			Cookie cookie = new Cookie("JSESSIONID", session.getId());
			cookie.setMaxAge(60*30);
			cookie.setPath("/web-chapter05");
			response.addCookie(cookie);
		}
	}

	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		doGet(request, response);
	}

}

三、创建LoginServlet类

在cn.itcast.chapter05.session.example02的包中创建LoginServlet类，该类是显示网站的登录页

package cn.itcast.chapter05.session.example02;

import java.io.*;
import javax.servlet.ServletException;
import javax.servlet.http.*;

public class LoginServlet extends HttpServlet {
	private static final long serialVersionUID = 1L;
	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		//解决乱码问题
		response.setContentType("text/html;charset=utf-8");
		String username = request.getParameter("username");
		String password = request.getParameter("password");
		PrintWriter pw = response.getWriter();
		if(("itcast").equals(username)&&("123456").equals(password)) {
			User user = new User();
			user.setUsername(username);
			user.setPassword(password);
			request.getSession().setAttribute("user", user);
			response.sendRedirect("/web-chapter05/IndexServlet");
		}else {
			pw.write("用户名或者密码错误，登录失败");
		}
	}

	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		
		doGet(request, response);
	}

}

四、创建LogoutServlet类

在cn.itcast.chapter05.session.example02的包中创建LogoutServlet类，该类是显示网站的退出及注销页面

package cn.itcast.chapter05.session.example02;

import java.io.*;
import javax.servlet.ServletException;
import javax.servlet.http.*;

public class LogoutServlet extends HttpServlet {
	private static final long serialVersionUID = 1L;
	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		//将session对象中的user对象移除,之后重定向到首页
		request.getSession().removeAttribute("user");
		response.sendRedirect("/web-chapter05/IndexServlet");
	}

	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		
		doGet(request, response);
	}

}

五、创建登录页面

在web-chapter05项目的WebContent目录下创建一个名为login.html的页面

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" 
                           "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
</head>
<body>
	<form name="reg" action="/web-chapter05/LoginServlet" method="post">
		用户名: <input name="username" type="text" /><br/>
		密&nbsp;&nbsp;码：<input name="password" type="password" /><br/>
				
			    <input type="submit" value="提交" id="bt" />
	</form>
</body>
</html>

六、在web.xml中配置相关的三个servlet

 <servlet>
    <description></description>
    <display-name>IndexServlet</display-name>
    <servlet-name>IndexServlet</servlet-name>
    <servlet-class>cn.itcast.chapter05.session.example02.IndexServlet</servlet-class>
  </servlet>
  <servlet-mapping>
    <servlet-name>IndexServlet</servlet-name>
    <url-pattern>/IndexServlet</url-pattern>
  </servlet-mapping>
  <servlet>
    <description></description>
    <display-name>LoginServlet</display-name>
    <servlet-name>LoginServlet</servlet-name>
    <servlet-class>cn.itcast.chapter05.session.example02.LoginServlet</servlet-class>
  </servlet>
  <servlet-mapping>
    <servlet-name>LoginServlet</servlet-name>
    <url-pattern>/LoginServlet</url-pattern>
  </servlet-mapping>
  <servlet>
    <description></description>
    <display-name>LogoutServlet</display-name>
    <servlet-name>LogoutServlet</servlet-name>
    <servlet-class>cn.itcast.chapter05.session.example02.LogoutServlet</servlet-class>
  </servlet>
  <servlet-mapping>
    <servlet-name>LogoutServlet</servlet-name>
    <url-pattern>/LogoutServlet</url-pattern>
  </servlet-mapping>

七、启动tomcat，在浏览器测试

在浏览器网址栏中输入http://localhost:8080/web-chapter05/login.html，进入下面的界面

然后输入之前在程序中设定好的账号itcast，和密码123456，进入下面的界面

点击退出链接就会进入下面的界面

如果点击登录的话就会接着进入登录的界面

至此，一个简单的模拟实现用户登录就完成了