利用servlet创建session,并设置权限

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Session其实指的就是访问者从到达某个特定主页到离开为止的那段时间。每一访问者都会单独获得一个Session。在Web应用程序中，当一个用户访问该应用时，Session类型的变量可以供这个用户在该Web应用的所有页面中共享数据；如果另一个用户也同时访问该Web应用，他也拥有自己的Session变量，但两个用户之间无法通过Session变量共享信息。

1。创建一个JAVA类，名称User.java，放在user包下

package user;

public class User {

private String username;

private String login;

public String getLogin() {

return login;

}

public void setLogin(String login) {

this.login = login;

}

public String getuserName() {

return username;

}

public void setuserName(String name) {

this.username = name;

}

2。创建一个servlet，名称：SessionId，放在test包下，主要功能：创建一个session，并且显示sessionid，在session中存入user信息。

package test;

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;

import user.User;

public class SessionId extends HttpServlet {

/**

* The doGet method of the servlet.

* This method is called when a form has its tag value method equals to get.

* @param request the request send by the client to the server

* @param response the response send by the server to the client

* @throws ServletException if an error occurred

* @throws IOException if an error occurred

public void doGet(HttpServletRequest request, HttpServletResponse response)

throws ServletException, IOException {

//String sessionId = request.getRequestedSessionId();

HttpSession session = request.getSession();

String sessionId = session.getId();

User user = new User();

user.setuserName("tom");

user.setLogin("true");

session.setAttribute("user", user);

response.setContentType("text/html");

PrintWriter out = response.getWriter();

out

.println("<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">");

out.println("<HTML>");

out.println(" <HEAD><TITLE>A Servlet</TITLE></HEAD>");

out.println(" <BODY>");

out.print(" This is ");

out.print(this.getClass());

out.println(", using the GET method");

out.println(" ");

out.println(sessionId);

out.println(" ");

out.println("<a href = "" + response.encodeURL("DeleteAll") + "" target = _blank> new page </a>");

out.println(" ");

out.println(" </BODY>");

out.println("</HTML>");

out.flush();

out.close();

System.out.println("*************************" + user.getuserName());

}

/**

* The doPost method of the servlet.

* This method is called when a form has its tag value method equals to post.

* @param request the request send by the client to the server

* @param response the response send by the server to the client

* @throws ServletException if an error occurred

* @throws IOException if an error occurred

public void doPost(HttpServletRequest request, HttpServletResponse response)

throws ServletException, IOException {

this.doGet(request, response);

}

主要代码：
  HttpSession session = request.getSession();
  String sessionId = session.getId();
  User user = new User();
  user.setuserName("tom");
  user.setLogin("true");
  session.setAttribute("user", user);

3。创建一个servlet，名称DeleteAll，在test包下，主要功能：设置权限

package test;

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;

import javax.xml.registry.JAXRException;

import user.User;

public class DeleteAll extends HttpServlet {

/**

* The doGet method of the servlet.

* This method is called when a form has its tag value method equals to get.

* @param request the request send by the client to the server

* @param response the response send by the server to the client

* @throws ServletException if an error occurred

* @throws IOException if an error occurred

* @throws JAXRException

public void doGet(HttpServletRequest request, HttpServletResponse response)

throws ServletException, IOException {

HttpSession httpSession = request.getSession();

String sessionid = httpSession.getId();

User user = (User) httpSession.getAttribute("user");

System.out.println("---------------------" + user.getuserName());

response.setContentType("text/html");

PrintWriter out = response.getWriter();

out

.println("<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">");

out.println("<HTML>");

out.println(" <HEAD><TITLE>A Servlet</TITLE></HEAD>");

out.println(" <BODY>");

out.print(" This is ");

out.print(this.getClass());

out.println(", using the GET method");

out.println(" ");

if (user == null) {

out.println("sorry,u must login again.");

}else{

out.println(user.getuserName() + " u can delete all");

}

out.println(", "+ sessionid + " ");

out.println(" </BODY>");

out.println("</HTML>");

out.flush();

out.close();

}

/**

* The doPost method of the servlet.

* This method is called when a form has its tag value method equals to post.

* @param request the request send by the client to the server

* @param response the response send by the server to the client

* @throws ServletException if an error occurred

* @throws IOException if an error occurred

public void doPost(HttpServletRequest request, HttpServletResponse response)

throws ServletException, IOException {

this.doGet(request, response);

}

主要代码：
User user = (User) httpSession.getAttribute("user");

if (user == null) {
   out.println("sorry,u must login again.");
  }else{
   out.println(user.getuserName() + " u can delete all");
  }

5。浏览器中运行，如果从SessionId中转入DeleteAll中，则会显示：

tom u can delete all ,

如果直接打开DeleteAll，则会显示：

sorry,u must login again。