08-2 Session

時間  2019-11-15
標籤 session 欄目 網站開發 简体版
原文   原文鏈接

第5節 Session快速入門

Session快速入門

1. 概念：服務器端會話技術，在一次會話的屢次請求間共享數據，將數據保存在服務器端的對象中。HttpSession
2. 快速入門：
    1. 獲取HttpSession對象：
        HttpSession session = request.getSession();
    2. 使用HttpSession對象：
        Object getAttribute(String name)  
        void setAttribute(String name, Object value)
        void removeAttribute(String name)

package cn.itcast.session;html

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import java.io.IOException;java

@WebServlet("/sessionDemo1")
public class SessionDemo1 extends HttpServlet {web

protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    //使用session共享數據

    //1.獲取session
    HttpSession session = request.getSession();
    //2.存儲數據
    session.setAttribute("msg","hello session");
}

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

}
package cn.itcast.session;數據庫

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import java.io.IOException;瀏覽器

@WebServlet("/sessionDemo2")
public class SessionDemo2 extends HttpServlet {tomcat

protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    //使用session獲取數據

    //1.獲取session
    HttpSession session = request.getSession();
    //2.獲取數據
    Object msg = session.getAttribute("msg");
    System.out.println(msg);
}

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

}安全

Session原理分析

  • Session的實現是依賴於Cookie的。

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第6節 Session細節

當客戶端關閉後，服務器不關閉，兩次獲取session是否爲同一個？

* 默認狀況下。不是。
        * 若是須要相同，則能夠建立Cookie,鍵爲JSESSIONID，設置最大存活時間，讓cookie持久化保存。
             Cookie c = new Cookie("JSESSIONID",session.getId());
             c.setMaxAge(60*60);
             response.addCookie(c);

package cn.itcast.session;服務器

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.*;
import java.io.IOException;cookie

@WebServlet("/sessionDemo3")
public class SessionDemo3 extends HttpServlet {session

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

    //1.獲取session
    HttpSession session = request.getSession();
    System.out.println(session);
    //以上關閉瀏覽器後再執行打印的session不是同一個,可是設置了下邊的代碼之後打印的session是同一個了

    //指望客戶端關閉後，session也能相同
    Cookie c = new Cookie("JSESSIONID",session.getId());
    c.setMaxAge(60*60);
    response.addCookie(c);

}

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

}
package cn.itcast.session;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.*;
import java.io.IOException;

@WebServlet("/sessionDemo4")
public class SessionDemo4 extends HttpServlet {

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

    //1.獲取session
    HttpSession session = request.getSession();
    System.out.println(session);

}

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

}

客戶端不關閉，服務器關閉後，兩次獲取的session是同一個嗎？

* 不是同一個，可是要確保數據不丟失。tomcat自動完成如下工做
            * session的鈍化：
                * 在服務器正常關閉以前，將session對象系列化到硬盤上
            * session的活化：
                * 在服務器啓動後，將session文件轉化爲內存中的session對象便可。

將out工做目錄下的項目打包成war文件夾

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把war文件夾放到tomcat的webapp目錄

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關掉idea本地的tomcat
啓動tomcat
訪問locahost:8080/day16/sessionDemo1
而後訪問localhost:8080/day16/sessionDemo2
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正常關閉服務器

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從新啓動後session的序列化文件刪除 內容從新還原到內存中了

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那麼在idea的Catalina_base的目錄是相似於
C:UsersAdministrator.IntelliJIdea2019.2systemtomcat_learn

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在idea重啓tomcat的目錄的時候會把work目錄刪掉

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等一會會建立一個work文件，可是文件中沒有對應的session文件了

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session何時被銷燬？

1. 服務器關閉
        2. session對象調用invalidate() 。
        3. session默認失效時間 30分鐘
            選擇性配置修改    
            <session-config>
                <session-timeout>30</session-timeout>
            </session-config>

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session的特色

1. session用於存儲一次會話的屢次請求的數據，存在服務器端
     2. session能夠存儲任意類型，任意大小的數據

    * session與Cookie的區別：
        1. session存儲數據在服務器端，Cookie在客戶端
        2. session沒有數據大小限制，Cookie有
        3. session數據安全，Cookie相對於不安全

第7節 Session之驗證碼案例

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login.jsp

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>

<title>login</title>


<script>
    window.onload = function(){
        document.getElementById("img").onclick = function(){
            this.src="/day16/checkCodeServlet?time="+new Date().getTime();
        }
    }


</script>
<style>
    div{
        color: red;
    }

</style>

</head>
<body>

<form action="/day16/loginServlet" method="post">
    <table>
        <tr>
            <td>用戶名</td>
            <td><input type="text" name="username"></td>
        </tr>
        <tr>
            <td>密碼</td>
            <td><input type="password" name="password"></td>
        </tr>
        <tr>
            <td>驗證碼</td>
            <td><input type="text" name="checkCode"></td>
        </tr>
        <tr>
            <td colspan="2"><img id="img" src="/day16/checkCodeServlet"></td>
        </tr>
        <tr>
            <td colspan="2"><input type="submit" value="登陸"></td>
        </tr>
    </table>


</form>


<div><%=request.getAttribute("cc_error") == null ? "" : request.getAttribute("cc_error")%></div>
<div><%=request.getAttribute("login_error") == null ? "" : request.getAttribute("login_error") %></div>

</body>
</html>

success.jsp

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>

<title>Title</title>

</head>
<body>

<h1><%=request.getSession().getAttribute("user")%>,歡迎您</h1>

</body>
</html>

LoginServlet.java

package cn.itcast.servlet;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import java.io.IOException;

@WebServlet("/loginServlet")
public class LoginServlet extends HttpServlet {

protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    //1.設置request編碼
    request.setCharacterEncoding("utf-8");
    //2.獲取參數
    String username = request.getParameter("username");
    String password = request.getParameter("password");
    String checkCode = request.getParameter("checkCode");
    //3.先獲取生成的驗證碼
    HttpSession session = request.getSession();
    String checkCode_session = (String) session.getAttribute("checkCode_session");
    //刪除session中存儲的驗證碼
    session.removeAttribute("checkCode_session");
    //3.先判斷驗證碼是否正確
    if(checkCode_session!= null && checkCode_session.equalsIgnoreCase(checkCode)){
        //忽略大小寫比較
        //驗證碼正確
        //判斷用戶名和密碼是否一致
        if("zhangsan".equals(username) && "123".equals(password)){//須要調用UserDao查詢數據庫
            //登陸成功
            //存儲信息，用戶信息
            session.setAttribute("user",username);
            //重定向到success.jsp
            response.sendRedirect(request.getContextPath()+"/success.jsp");
        }else{
            //登陸失敗
            //存儲提示信息到request
            request.setAttribute("login_error","用戶名或密碼錯誤");
            //轉發到登陸頁面
            request.getRequestDispatcher("/login.jsp").forward(request,response);
        }


    }else{
        //驗證碼不一致
        //存儲提示信息到request
        request.setAttribute("cc_error","驗證碼錯誤");
        //轉發到登陸頁面
        request.getRequestDispatcher("/login.jsp").forward(request,response);

    }

}

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

}

CheckCodeServlet.java

package cn.itcast.servlet;

import javax.imageio.ImageIO;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.awt.*;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.util.Random;

@WebServlet("/checkCodeServlet")
public class CheckCodeServlet extends HttpServlet {

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


    int width = 100;
    int height = 50;

    //1.建立一對象，在內存中圖片(驗證碼圖片對象)
    BufferedImage image = new BufferedImage(width,height,BufferedImage.TYPE_INT_RGB);


    //2.美化圖片
    //2.1 填充背景色
    Graphics g = image.getGraphics();//畫筆對象
    g.setColor(Color.PINK);//設置畫筆顏色
    g.fillRect(0,0,width,height);

    //2.2畫邊框
    g.setColor(Color.BLUE);
    g.drawRect(0,0,width - 1,height - 1);

    String str = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghigklmnopqrstuvwxyz0123456789";
    //生成隨機角標
    Random ran = new Random();
    StringBuilder sb = new StringBuilder();
    for (int i = 1; i <= 4; i++) {
        int index = ran.nextInt(str.length());
        //獲取字符
        char ch = str.charAt(index);//隨機字符
        sb.append(ch);

        //2.3寫驗證碼
        g.drawString(ch+"",width/5*i,height/2);
    }
    String checkCode_session = sb.toString();
    //將驗證碼存入session
    request.getSession().setAttribute("checkCode_session",checkCode_session);

    //2.4畫干擾線
    g.setColor(Color.GREEN);

    //隨機生成座標點

    for (int i = 0; i < 10; i++) {
        int x1 = ran.nextInt(width);
        int x2 = ran.nextInt(width);

        int y1 = ran.nextInt(height);
        int y2 = ran.nextInt(height);
        g.drawLine(x1,y1,x2,y2);
    }


    //3.將圖片輸出到頁面展現
    ImageIO.write(image,"jpg",response.getOutputStream());


}

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

}

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