jsp入门+Cookie+HttpSession - 跳动de手指

jsp入门：

如何在jsp中插入java脚本：

<% java代码%>：方法体里面可以有什么这里面就能放什么。（常用）

<%=变量%>：sysout（）；输出语句中可以放什么，这里面就能放什么，常用来显示变量（常用）

<%! %>：类里面可以放什么这里面就能放什么，但是不准使用，（过时了）

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%
String path = request.getContextPath();
/*java 代码片段
*/
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>
<%--JSP是由HTML+JAVA代码+标签（命令）组成的，
实现了Servlet接口的一个Servlet体系类，由服务器编译创
建对象，调用service（）方法，其本质就是一个Servlet；
JSP是用来发送超链接或者表单请求的页面，servlet处理数据
，同时将结果转发回JSP页面 --%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  <head>
    <base href="<%=basePath%>">
    
    <title>My JSP 'index.jsp' starting page</title>
    <meta http-equiv="pragma" content="no-cache">
    <meta http-equiv="cache-control" content="no-cache">
    <meta http-equiv="expires" content="0">    
    <meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
    <meta http-equiv="description" content="This is my page">
    <!--
    <link rel="stylesheet" type="text/css" href="styles.css">
    -->
  </head>
  
  <body>
   <h3>计算器网页版:</h3><br>
   <form action="/day_11/AddServlet"method="post">
       <table  align="center" width="60%">
   <%
   int x=0;
   for(int i =x;i<3;i++){
   %>
       <tr>
       <%
       int y = 0;
       for(int j =x;j<x+3;j++){
       %>
       <td><input type="button" value="<%=j %>" name="num_<%=j %>"></td>
       <% 
       y=j;}x=y+1;
       %>
       </tr>
       <%
   } 
       %>
       <tr><td><input type="button" value="9"/></td></tr>
       </table>
       <br/><hr/>
       <input type="button" value="+" name="add"/>
       <input type="button" value="-" name="sub"/>
       <input type="button" value="*" name="mul"/>
       <input type="button" value="/" name="div"/>
       <input type="submit" value="=" />
       <br/><hr/>
       result:<input type="text" name="value"/>
       <hr/>
   </form>
  </body>
</html>

使用jsp完成一个加法运算页面：

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  <head>
    <base href="<%=basePath%>">
    
    <title>My JSP 'add.jsp' starting page</title>
    
    <meta http-equiv="pragma" content="no-cache">
    <meta http-equiv="cache-control" content="no-cache">
    <meta http-equiv="expires" content="0">    
    <meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
    <meta http-equiv="description" content="This is my page">
    <!--
    <link rel="stylesheet" type="text/css" href="styles.css">
    -->

  </head>
  
  <body>
    This is my JSP page. <br>
    <form action="/day_11/AddServlet" method="post">
        数字A:<input type="text" name="num1" value="123"/><br/>
        数字B:<input type="text" name="num2" value="456"/><br/>
        <input type="submit" value="提交"/>
    </form>
  </body>
</html>

package cn.Jsp.wyx;

import java.io.IOException;
import java.util.Enumeration;

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

public class AddServlet extends HttpServlet {

    /**
     * 
     */
    private static final long serialVersionUID = 1L;

    public void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
            request.setCharacterEncoding("utf-8");
            String value1 = request.getParameter("num1");
            String value2 = request.getParameter("num2");
            int A = Integer.parseInt(value1);
            int B = Integer.parseInt(value2);
            request.setAttribute("result", A+B);
            request.getRequestDispatcher("/result.jsp").forward(request, response);
    }

}

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  <head>
    <base href="<%=basePath%>">
    
    <title>My JSP 'result.jsp' starting page</title>
    
    <meta http-equiv="pragma" content="no-cache">
    <meta http-equiv="cache-control" content="no-cache">
    <meta http-equiv="expires" content="0">    
    <meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
    <meta http-equiv="description" content="This is my page">
    <!--
    <link rel="stylesheet" type="text/css" href="styles.css">
    -->

  </head>
  
  <body>
    This is my JSP page. <br>
    <% 
    Integer result = (Integer)request.getAttribute("result");
    %>
    <input type="text" name="result" value="<%=result %>"/>
  </body>
</html>

jsp页面提供了表单，servlet拿到表单数据进行处理并将处理后的结果发送给另一个显示结果的jsp页面；

Cookie介绍：

package cn.Cookie.wyx;

import java.io.IOException;

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

public class ACookieServlet extends HttpServlet {

    /**
     * Cookie 三大元素：
     * 1、生命周期:setMaxAge(60*60*24)通过此方法设置
     * 2、路径：可以通过浏览器安全选项查看，也可以设置setPath（uri）,
     * JSESSIONID默认保存在项目路径下，浏览器通过判断访问者的URL是否
     * 包含cookie路径，来判断给服务端发送哪些cookie。
     * （只有包含cookie路径的URL客户端才会发送这个cookie给服务端）
     * 3、cookie保存机制：保存于客户端
     */
    private static final long serialVersionUID = 1L;
    
    public void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
            response.setContentType("text/html;charset=utf-8");
            Cookie cookie = new Cookie("aaa", "AAA");
            cookie.setPath("/day_11/");//uri路径
            cookie.setMaxAge(60*60*24);//24小时
            response.addCookie(cookie);//向客户端发送一个Cookie
    }

}

package cn.Cookie.wyx;

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

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

public class BCookieServlet extends HttpServlet {

    public void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
            Cookie[] cookies = request.getCookies();
            if(cookies!=null){
                for (int i = 0; i < cookies.length; i++) {
                    String name = cookies[i].getName();
                    String value = cookies[i].getValue();
                    System.out.println("cookieName:"+name+"cookieValue:"+value);
                }
            }
    }

}

<%@page import="java.net.CookieStore"%>
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  <head>
    <base href="<%=basePath%>">
    
    <title>My JSP 'cookie.jsp' starting page</title>
    
    <meta http-equiv="pragma" content="no-cache">
    <meta http-equiv="cache-control" content="no-cache">
    <meta http-equiv="expires" content="0">    
    <meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
    <meta http-equiv="description" content="This is my page">
    <!--
    <link rel="stylesheet" type="text/css" href="styles.css">
    -->

  </head>
  
  <body>
    This is my JSP page. <br>
    <%
    /*
        jsp中九大内置对象，默认初始化了HttpSession对象，当调用getSeesion（）时，就会创建一个叫JSESSIONID的Cookie;
    */
    Cookie[]cookies = request.getCookies();
        if(cookies!=null){
            for(Cookie c:cookies){
                String value = c.getValue();
                out.print(value+"<br/>");
            }
        }
    %>
  
  </body>
</html>

当用户访问第一个servlet时，response对象会向客户端发送一个Cookie，并保存在本地磁盘24小时；访问第二个servlet时取出Cookie;因为cookie.jsp路径包含Cookie的路径，

所以在访问cookie.jsp时，也会带着上一次保存的cookie，同时jsp内置session对象，一定调用了request.getSession()方法，没有发现JSESSIONID，同时创建这个cookie；

第二次访问cookie.jsp的时候，就会读取到两个cookie；

HttpSession:

package cn.HttpSession.wyx;

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;

public class HttpSessionTest extends HttpServlet {

    
    /**
     * 
     */
    private static final long serialVersionUID = 1L;

    public void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        /**
         * 获取session,
         * session原理：
         * session底层依赖Cookie或者URL重写，当调用request.getSession()，服务器会进行判断；
         * 首先会去拿一个叫JSESSIONID的Cookie；没有这个Cookie，会去URL中拿一个JSESSIONID的参数；
         * 如果拿到，会去服务器中找是否有对应的session信息，
         * 如果没有会创建一个新的session，并将JSESSIONID保存到cookie中。
         * 如果有会直接得到session，不创建；
         * 
         * */
            HttpSession session = request.getSession();
            //获取JSESSIONID
            String JSESSIONID = session.getId();
            //向session中保存数据，session域在一个会话中；
            session.setAttribute("sessionValue","hello");
    }

}

package cn.HttpSession.wyx;

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;

public class HttpSessionTest2 extends HttpServlet {

    private static final long serialVersionUID = 1L;

    public void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
            HttpSession session = request.getSession();
            /*
             * 取出session域中数据;
             * Servlet中三大域：
             * request(作用域为一个请求内)
             * session(作用域为一个会话内)
             * ServletContext(作用域为整个项目，只要不关闭TOMCAT，它就一直在)
             * */
            String sessionValue = (String)session.getAttribute("sessionValue");
            System.out.println(sessionValue);
    }

}

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  <head>
    <base href="<%=basePath%>">
    
    <title>My JSP 'EncodeURL.jsp' starting page</title>
    
    <meta http-equiv="pragma" content="no-cache">
    <meta http-equiv="cache-control" content="no-cache">
    <meta http-equiv="expires" content="0">    
    <meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
    <meta http-equiv="description" content="This is my page">
    <!--
    <link rel="stylesheet" type="text/css" href="styles.css">
    -->

  </head>
  
  <body>
    <a href="/day_11/HttpSessionTest;JSESSIONID=<%=session.getId()%>">URL重写测试</a>
    <%
    //他会查看cookie是否存在，如果不存在，在指定的url后添加JSESSIONID参数,如果存在，它就不会添加；
    //在每个url后面都加上这段代码response.encodeURL("uri路径")，就自动实现了url重写；
    out.print(response.encodeURL("/day_11/HttpSessionTest"));
    %>
  </body>
</html>

这个功能可以熟练应用request、session、Cookie；

HttpSession request.getSession(); 从request对象中得到session

Cookie[] request.getCookies(); 从request对象中得到cookie

response.addCookie(Cookie cookie); 向客户端保存一个cookie

1、提供登录页面，form，错误信息收集及显示；

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  <head>
    <base href="<%=basePath%>">
    
    <title>My JSP 'Login.jsp' starting page</title>
    
    <meta http-equiv="pragma" content="no-cache">
    <meta http-equiv="cache-control" content="no-cache">
    <meta http-equiv="expires" content="0">    
    <meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
    <meta http-equiv="description" content="This is my page">
    <!--
    <link rel="stylesheet" type="text/css" href="styles.css">
    -->

  </head>
  
  <body>
    This is my JSP page. <br>
    <%
//为了避免第一次访问网页出现显示null的现象，所以创建这个变量；

        String errormsg ="";
    %>
    <%
        String msg = (String)request.getAttribute("msg");
            if(msg!=null){
            errormsg=msg;
    }
        
    %>
    <%
    /*
    获取cookie中的值；
    */
    String uname = "";
    Cookie[]cookies=request.getCookies();
    for(Cookie c:cookies){
        if(c.getName().equalsIgnoreCase("username")){
            uname=c.getValue();
        }
    }
    %>
     <font color="red"><b><%=errormsg %></b></font>
    <form action="/day_11/LoginServlet" method="post">
        用户名:<input type="text" name="username"value = "<%=uname %>"/><br>
        密码:<input type="password" name="password"/><br/>
        <input type="submit" value="提交"/>  
    </form>
  </body>
</html>

2、创建servlet处理数据，重定向和转发请求（业务逻辑）

package cn.login.wyx;

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

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

public class LoginServlet extends HttpServlet {

    public void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
            response.setContentType("text/html;charset=utf-8");
            request.setCharacterEncoding("UTF-8");
            String username = request.getParameter("username");
            //将username保存到Cookie中
            Cookie cookie = new Cookie("username", username);
            cookie.setMaxAge(60*60*24);
            //发送Cookie给客户端
            response.addCookie(cookie); 
            //request.getParameter("password");
            if(!username.equals("wangyinxu")){
                //获取session
                HttpSession session = request.getSession();
                //将用户名存储到session域
                session.setAttribute("username", username);
                //重定向到成功页面
                response.sendRedirect("/day_11/succ1.jsp");
            }else {
                //保存错误信息到request
                request.setAttribute("msg", "用户名不存在");
                //转发到login.jsp
                request.getRequestDispatcher("/Login.jsp").forward(request, response);
            }
    }

}

3、登录成功页面

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  <head>
    <base href="<%=basePath%>">
    
    <title>My JSP 'succ1.jsp' starting page</title>
    
    <meta http-equiv="pragma" content="no-cache">
    <meta http-equiv="cache-control" content="no-cache">
    <meta http-equiv="expires" content="0">    
    <meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
    <meta http-equiv="description" content="This is my page">
    <!--
    <link rel="stylesheet" type="text/css" href="styles.css">
    -->

  </head>
  
  <body>
   <%
       String username = (String)session.getAttribute("username");
   if(username==null){
       request.setAttribute("msg", "请先登录");
       request.getRequestDispatcher("/Login.jsp").forward(request, response);
       return;
   }
   %>
   <font color="gray">欢迎-<%=username %>-登录：</font>
  </body>
</html>

发表于 2018-02-06 14:52 跳动de手指阅读(460) 评论(0) 编辑收藏举报