JSP与JSTL_jstl和jsp

配置好tomcat

WEB_INF目录下的web.xml

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd"
         version="4.0">

    <!--全局初始化参数=全局变量-->
    <context-param>
        <param-name>allparam</param-name>
        <param-value>allparam参数</param-value>
    </context-param>

    <servlet>
        <servlet-name>b1</servlet-name>
        <servlet-class>
        	//这里的web是src文件下web包里的UserServlet
            web.UsersServlet
        </servlet-class>
        <init-param>
            <!--针对某一个servle=局部变量-->
            <param-name>myparam</param-name>
            <param-value>myparam的值</param-value>
        </init-param>
    </servlet>
    <servlet-mapping>
        <servlet-name>b1</servlet-name>
        <url-pattern>/login</url-pattern>
    </servlet-mapping>

    <!--配置监听器-->
    <listener>
        <listener-class>util.SessionListener</listener-class>
    </listener>
    <listener>
        <listener-class>util.AttributeListener</listener-class>
    </listener>
</web-app>
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UserServlet

package web;

import bean.LoginInfo;
import dao.LoginInfoDao;
import dao.impl.LoginInfoDaoimpl;

import javax.servlet.ServletConfig;
import javax.servlet.ServletException;
import javax.servlet.http.*;
import java.io.IOException;
import java.io.PrintWriter;

public class UsersServlet extends HttpServlet {

    LoginInfoDao loginInfoDao = null;

    @Override
    public void init(ServletConfig config) throws ServletException {
    	//这里可以访问web.xml里配置的全局初始化参数和局部初始化参数
        //局部初始化参数
        System.out.println("UsersServlet-init->myparam"+
        config.getInitParameter("myparam"));
        
        //全局初始化参数
        System.out.println("UsersServlet-init->allparam"+
        config.getInitParameter("allparam"));
    }

    public UsersServlet() {
        loginInfoDao = new LoginInfoDaoimpl();
        int success = loginInfoDao.createUserInfoTable();
        success = loginInfoDao.addUserInfo(1,"admin","123");
    }

    @Override
    public void destroy() {
        System.out.println("UsersServlet销毁");
    }

    @Override
    public void init() throws ServletException {
        System.out.println("UsersServlet初始化");
    }

    @Override   //接收get请求：超链接
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //接收用户传递过来的参数
        String uage = req.getParameter("uage");
        String upass = req.getParameter("upass");
        System.out.println(uage+","+upass);
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //处理post请求的乱码
        req.setCharacterEncoding("utf-8");

        //接收用户传递过来的参数
        //无论前台传递什么格式的数据，后台都是使用String接收的
        String username = req.getParameter("username");
        String password = req.getParameter("password");
        String quit = req.getParameter("quit");

        HttpSession session= req.getSession();

        if(quit !=null && quit.equals("退出")){
            session.removeAttribute("username");
            session.removeAttribute("password");
            req.getRequestDispatcher("index.jsp").forward(req,resp);
            return;
        }

        Boolean success = loginInfoDao.queryUserInfo(username, password, LoginInfo.class);
        if(success){
            //登录成功
            session.setAttribute("username",username);
            session.setAttribute("password",password);
            System.out.println("帐号："+ username);
            System.out.println("密码："+ password);
            req.getRequestDispatcher("/success.jsp").forward(req,resp);
        }else {
            //登陆失败
            //1.后台创建cookie
            Cookie cookie = new Cookie("uname",username);
            //返回给前端
            resp.addCookie(cookie);
            resp.sendRedirect("index.jsp");
        }
    }
}

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login.jsp

//action里的login需要配置WEB_INF里的web.xml来进行调用
//当提交表单时，login在web.xml里绑定了mapping里的b1，
//b1找到servlet里的b1,再找到servlet-class，实例化UserServlet类
<form action="login" method="post">
    用户名:<input type="text" name="username" value="${unamecookie}" required>
    密码：<input type="password" name="password" required>
    <input type="submit" name="login" value="登录">
    <br>
    <h1>帐号：admin,密码：123,数据库：javaweb,表：login</h1>
  </form>
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test.jsp

<%@ page contentType="text/html;charset=UTF-8" language="java"
 errorPage="test2.jsp" %>
<html>
<head>
    <title>Title</title>
</head>
<body>

<%
    //某一次请求
    request.setAttribute("a1","aaa");
%>
request=<%= request.getAttribute("a1")%><br>
<% //response.sendRedirect(" ");
    response.getWriter();
%>
<%
    //整个会话期间
    session.setAttribute("b1","bbb");
%>
session=<%=session.getAttribute("b1")%><br>

<%
    //application表示的是整个（服务器）程序运行期间
    application.setAttribute("c1","ccc");
%>

application=<%=application.getAttribute("c1")%><br>

<% //page = this %>
<%
    //当前页面
    pageContext.setAttribute("d1","ddd");
%>
pageContext=<%=pageContext.getAttribute("d1")%>
<a href="test2.jsp">test2.jsp</a>

<%=6/0%>
</body>
</html>

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test2.jsp

<%@ page import="java.util.ArrayList" %>
<%@ page import="java.util.List" %>
<%@ page contentType="text/html;charset=UTF-8" language="java"
 isErrorPage="true" %>
<html>
<head>
    <title>Title</title>
</head>
<body>
<%
    List list = new ArrayList();
%>

    <h1>test2.jsp</h1>

    request=<%= request.getAttribute("a1")%><br>

    session=<%=session.getAttribute("b1")%><br>

    application=<%=application.getAttribute("c1")%><br>

    pageContext=<%=pageContext.getAttribute("d1")%>

    <% out.print("out---"); %>
    <% out.print("<script>alert('success');</script>"); %>
    <% config.getInitParameter("");%>
exception=<%= exception.getMessage() %>
</body>
</html>

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top.jsp

<%@ page import="java.util.ArrayList" %>
<%@ page import="java.util.List" %>
<%@ page import="java.util.HashMap" %>
<%@ page import="java.util.Map" %>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
</head>
<body>
    <h1>top.jsp</h1>
    <%
        //EL表达式如果想要读取变量，则该变量一定要在作用域中：pageContext,request,session,application
        int a=10;
        pageContext.setAttribute("a1",a);
        List list = new ArrayList();
        list.add("abc");
        pageContext.setAttribute("a2",list);
        Map map = new HashMap();
        map.put("k1","key");
        pageContext.setAttribute("a3",map);
        //如果在相同的key的前提下，不同的作用域,el表达式会选择展示哪个值
        pageContext.setAttribute("a4","pageContext内容");
        request.setAttribute("a4","request内容");
        session.setAttribute("a4","session内容");
        application.setAttribute("a4","application内容");
    %>
${20+30}<br>
${20>30}<br>
${20<30}<br>
${20>30?"aaa":"bbb"}<br>
a=${a1}<br>
    abc=${a2[0]}<br>
k1=${a3.k1}<br>
a4=${a4}<br>
    pageContext-a4=${pageScope.a4}<br>
    request-a4=${requestScope.a4}<br>
    session-a4=${sessionScope.a4}<br>
    application-a4=${applicationScope.a4}<br>

</body>
</html>

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all.jsp

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
</head>
<body>
    <%@include file="top.jsp"%>
</body>
</html>

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jstltest.jsp

<%@ page import="java.util.List" %>
<%@ page import="java.util.ArrayList" %>
<%@ page import="java.util.Date" %>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<%@taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<%@taglib prefix="fmt" uri="http://java.sun.com/jsp/jstl/fmt" %>
<html>
<head>
    <title>Title</title>
</head>
<body>
    <h1>jstl</h1>
    <c:set var="uname" value="张三" scope="session"></c:set>
    <c:out value="${sessionScope.uname}"></c:out>

<c:if test="${uname=='张三'}">
    这是张三
</c:if>
<c:choose>
    <c:when test="${uname=='张三'}">
        c-choose-张三
    </c:when>
    <c:otherwise>
        c-choose-不是张三
    </c:otherwise>
</c:choose>
<%
    List list = new ArrayList();
    list.add("abc");
    list.add("bcd");
    list.add("1李四");
    pageContext.setAttribute("ulist",list);
%>
<h4>循环数据</h4>
<c:forEach items="${ulist}" var="user" varStatus="sta">
    ${sta.count}-${sta.index}--->   ${user}<br>
</c:forEach>
<%
    pageContext.setAttribute("mytime",new Date());
%>
date=<fmt:formatDate value="${mytime}" pattern="yyyy-MM-dd"></fmt:formatDate>
</body>
</html>

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