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>
登录>servlet校验>登录成功：
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>