Web开发15：Session在现实项目中的应用 _Web前端

Web开发15：Session在实际项目中的应用

写一个登录例子：

用户在login.jsp页面登录，如果用户名是zhangsan，密码为123，并且选择的普通用户，则登录成功。或用户名是lisi，密码为456，且选择的是管理员，则登录成功。如果登录失败，则返回到登录页面，并且在登录页面保留之前输入过的用户名及选择的用户类型。

User.java???

package com.test.bean;

public class User {
	private String username;
	private String password;
	private String authority;

	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;
	}

	public String getAuthority() {
		return authority;
	}

	public void setAuthority(String authority) {
		this.authority = authority;
	}
}

<%@ page language="java" import="java.util.*" pageEncoding="utf-8"%>
<html>
  <body>
  	<%String authority = (String)request.getAttribute("authority"); %>
	<form action="/servletTest/UserLoginServlet" method="post">
		用户名：<input type="text" name="username" value="<%= null == request.getAttribute("username") ? "": request.getAttribute("username")%>"/><br>
		密码：<input type="password" name="password"/><br>
		authority:
		<select name="authority">
			<option value="1" <%= "1".equals(authority)? "selected":""%>>common user</option>
			<option value="2" <%= "2".equals(authority)? "selected":""%>>administrator</option> 
		</select><br>
		<input type="submit" value="submit">
	</form>
  </body>
</html>

UserLoginServlet.java

package com.test.servlet;

import java.io.IOException;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

import com.test.bean.User;

public class UserLoginServlet extends HttpServlet {

	public void doPost(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		String username = request.getParameter("username");
		String password = request.getParameter("password");
		String authority = request.getParameter("authority");
		if("1".equals(authority)){
			//登录的是普通用户
			if("zhangsan".equals(username) && "123".equals(password)){
				User user = new User();
				user.setUsername(username);
				user.setPassword(password);
				user.setAuthority(authority);
				HttpSession session = request.getSession();
				session.setAttribute("user", user);
				request.getRequestDispatcher("/session/index.jsp").forward(request, response);
			}else{//登录失败
				request.setAttribute("username", username);
				request.setAttribute("password", password);
				request.setAttribute("authority", authority);
				request.getRequestDispatcher("session/login.jsp").forward(request, response);
			}
		}
		else if("2".equals(authority)){
			//登录的系统管理员
			if("lisi".equals(username) && "456".equals(password)){
				User user = new User();
				user.setUsername(username);
				user.setPassword(password);
				user.setAuthority(authority);
				HttpSession session = request.getSession();
				session.setAttribute("user", user);
				request.getRequestDispatcher("/session/index.jsp").forward(request, response);
			}else{//登录失败
				request.setAttribute("username", username);
				request.setAttribute("password", password);
				request.setAttribute("authority", authority);
				request.getRequestDispatcher("session/login.jsp").forward(request, response);
			}
		}else{
			request.setAttribute("username", username);
			request.setAttribute("password", password);
			request.setAttribute("authority", authority);
			request.getRequestDispatcher("session/login.jsp").forward(request, response);
		}
	}
	
	protected void doGet(HttpServletRequest req, HttpServletResponse resp)
			throws ServletException, IOException {
		super.doGet(req, resp);
	}
}

以上servlet也可以改为重定向的方式实现：

response.sendRedirect("login.jsp?username="+username+"&password="+password);

在login.jsp页面必须改为request.getParameter()来接收servlet转回的username及password。?

index.jsp 显示两个链接:query和update，只有管理员才显示update链接

<%@ page language="java" import="com.test.bean.*" pageEncoding="UTF-8"%>
<html>
  <body>
  	<%
  		User user = (User)session.getAttribute("user");
  		if(null == user){
  			response.sendRedirect("login.jsp");
  			return;
  		}
  	 %>
  	<a href="QueryServlet">query</a><br>
  	<!--只有管理员才显示update链接  -->
  	<%if(((User)session.getAttribute("user")).getAuthority().equals("2")){ %>
  		<a href="UpdateServlet">update</a><br>
  	<%} %>
  </body>
</html>

QueryServlet.java

package com.test.servlet;

import java.io.IOException;
import java.io.PrintWriter;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

public class QueryServlet extends HttpServlet {
	public void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		HttpSession session = request.getSession();
		//如果 session中没有用户，则重定向到登录页面
		if(null == session.getAttribute("user")){
			response.sendRedirect("session/login.jsp");
			return;
		}
		response.getWriter().print("welcome");
	}

}