JSP技术开发

/*
 * Generated by the Jasper component of Apache Tomcat
 * Version: Apache Tomcat/9.0.70
 * Generated at: 2023-02-06 08:11:44 UTC
 * Note: The last modified time of this file was set to
 *       the last modified time of the source file after
 *       generation to assist with modification tracking.
 */
package org.apache.jsp;

import javax.servlet.*;
import javax.servlet.http.*;
import javax.servlet.jsp.*;

public final class index_jsp extends org.apache.jasper.runtime.HttpJspBase
    implements org.apache.jasper.runtime.JspSourceDependent,
                 org.apache.jasper.runtime.JspSourceImports {

  private static final javax.servlet.jsp.JspFactory _jspxFactory =
          javax.servlet.jsp.JspFactory.getDefaultFactory();

  private static java.util.Map<java.lang.String,java.lang.Long> _jspx_dependants;

  private static final java.util.Set<java.lang.String> _jspx_imports_packages;

  private static final java.util.Set<java.lang.String> _jspx_imports_classes;

  static {
    _jspx_imports_packages = new java.util.HashSet<>();
    _jspx_imports_packages.add("javax.servlet");
    _jspx_imports_packages.add("javax.servlet.http");
    _jspx_imports_packages.add("javax.servlet.jsp");
    _jspx_imports_classes = null;
  }

  private volatile javax.el.ExpressionFactory _el_expressionfactory;
  private volatile org.apache.tomcat.InstanceManager _jsp_instancemanager;

  public java.util.Map<java.lang.String,java.lang.Long> getDependants() {
    return _jspx_dependants;
  }

  public java.util.Set<java.lang.String> getPackageImports() {
    return _jspx_imports_packages;
  }

  public java.util.Set<java.lang.String> getClassImports() {
    return _jspx_imports_classes;
  }

  public javax.el.ExpressionFactory _jsp_getExpressionFactory() {
    if (_el_expressionfactory == null) {
      synchronized (this) {
        if (_el_expressionfactory == null) {
          _el_expressionfactory = _jspxFactory.getJspApplicationContext(getServletConfig().getServletContext()).getExpressionFactory();
        }
      }
    }
    return _el_expressionfactory;
  }

  public org.apache.tomcat.InstanceManager _jsp_getInstanceManager() {
    if (_jsp_instancemanager == null) {
      synchronized (this) {
        if (_jsp_instancemanager == null) {
          _jsp_instancemanager = org.apache.jasper.runtime.InstanceManagerFactory.getInstanceManager(getServletConfig());
        }
      }
    }
    return _jsp_instancemanager;
  }

  public void _jspInit() {
  }

  public void _jspDestroy() {
  }

  public void _jspService(final javax.servlet.http.HttpServletRequest request, final javax.servlet.http.HttpServletResponse response)
      throws java.io.IOException, javax.servlet.ServletException {

    if (!javax.servlet.DispatcherType.ERROR.equals(request.getDispatcherType())) {
      final java.lang.String _jspx_method = request.getMethod();
      if ("OPTIONS".equals(_jspx_method)) {
        response.setHeader("Allow","GET, HEAD, POST, OPTIONS");
        return;
      }
      if (!"GET".equals(_jspx_method) && !"POST".equals(_jspx_method) && !"HEAD".equals(_jspx_method)) {
        response.setHeader("Allow","GET, HEAD, POST, OPTIONS");
        response.sendError(HttpServletResponse.SC_METHOD_NOT_ALLOWED, "JSP 只允许 GET、POST 或 HEAD。Jasper 还允许 OPTIONS");
        return;
      }
    }

    final javax.servlet.jsp.PageContext pageContext;
    javax.servlet.http.HttpSession session = null;
    final javax.servlet.ServletContext application;
    final javax.servlet.ServletConfig config;
    javax.servlet.jsp.JspWriter out = null;
    final java.lang.Object page = this;
    javax.servlet.jsp.JspWriter _jspx_out = null;
    javax.servlet.jsp.PageContext _jspx_page_context = null;


    try {
      response.setContentType("text/html;charset=UTF-8");
      pageContext = _jspxFactory.getPageContext(this, request, response,
      			null, true, 8192, true);
      _jspx_page_context = pageContext;
      application = pageContext.getServletContext();
      config = pageContext.getServletConfig();
      session = pageContext.getSession();
      out = pageContext.getOut();
      _jspx_out = out;

      out.write("\n");
      out.write("\n");
      out.write("<html>\n");
      out.write("  <head>\n");
      out.write("    <title>$Title$</title>\n");
      out.write("  </head>\n");
      out.write("  <body>\n");
      out.write("  $END$\n");
      out.write("  </body>\n");
      out.write("</html>\n");
    } catch (java.lang.Throwable t) {
      if (!(t instanceof javax.servlet.jsp.SkipPageException)){
        out = _jspx_out;
        if (out != null && out.getBufferSize() != 0)
          try {
            if (response.isCommitted()) {
              out.flush();
            } else {
              out.clearBuffer();
            }
          } catch (java.io.IOException e) {}
        if (_jspx_page_context != null) _jspx_page_context.handlePageException(t);
        else throw new ServletException(t);
      }
    } finally {
      _jspxFactory.releasePageContext(_jspx_page_context);
    }
  }
}

<%--
  Created by IntelliJ IDEA.
  User: zhaoss-msb
  Date: 2023/2/6
  Time: 20:00
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
    <style>
        /*css的注释*/
        <%--JSP自身的注释--%>
    </style>
    <script>
        //js单行注释
        /*js多行注释*/
        <%--JSP自身的注释--%>
    </script>
</head>
<body>
    <!-- HTML的注释 -->
    <%--JSP自身的注释--%>
    <input type="text">
    <%--JSP自身的注释--%>
</body>
</html>

第一种：<%    %>： java 脚本段，可以定义局部变量、编写语句

第二种：<%!   %>：声明，可以定义全局（成员）变量、方法、类

第三种：<%=  %>：表达式，数据一个变量或具体内容

<%--
  Created by IntelliJ IDEA.
  User: zhaoss-msb
  Date: 2023/2/6
  Time: 20:39
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
</head>
<body>
    <%
        //java脚本段，这里可以编写java代码，这是单行注释
        /* java的多行注释：a以后在转译后的文件中会变成一个局部变量 */
        int a = 10;
    %>
    <%!
        // 声明：以后在转译后的文件中b会变成一个成员变量，servlet是单例的，所以成员变量很少使用。
        int b = 20;
        public void eat(){
            System.out.println("eat....");
        }
    %>
    this is a jsp..局部变量<%=a  %> 成员变量<%=b  %>
</body>
</html>

<%--
  Created by IntelliJ IDEA.
  User: zhaoss-msb
  Date: 2023/2/6
  Time: 21:36
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
</head>
<body>
    <jsp:include page="header.jsp"></jsp:include>
    <div style="height: 800px">
        京东页面实际代码逻辑。。。。
    </div>
    <jsp:include page="foot.jsp"></jsp:include>

</body>
</html>

<%--
  Created by IntelliJ IDEA.
  User: zhaoss-msb
  Date: 2023/2/6
  Time: 21:36
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
</head>
<body>
  <img src="imgs/header.png">
</body>
</html>

<%--
  Created by IntelliJ IDEA.
  User: zhaoss-msb
  Date: 2023/2/6
  Time: 21:36
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
</head>
<body>
  <img src="imgs/foot.png">
</body>
</html>

<%@ directive attribute="value" %>

<%--
  Created by IntelliJ IDEA.
  User: zhaoss-msb
  Date: 2023/2/6
  Time: 22:25
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java"
         pageEncoding="utf-8" import="java.util.*"
        errorPage="error.jsp" %>
<%--
contentType：给浏览器看的，浏览器解析jsp的编码格式：utf-8
language:设置jsp中脚本语言：java
pageEncoding:当前jsp页面的编码格式
import:导包
errorPage:指定错误页面，当页面发生错误的时候，显示错误页面的信息
--%>
<html>
<head>
    <title>Title</title>
</head>
<body>
    <%
        List list = new ArrayList();
        int a = 1/0;
    %>
</body>
</html>

<%--
  Created by IntelliJ IDEA.
  User: zhaoss-msb
  Date: 2023/2/6
  Time: 22:30
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
</head>
<body>
  现在服务器繁忙，请联系管理员！
</body>
</html>

<%--
  Created by IntelliJ IDEA.
  User: zhaoss-msb
  Date: 2023/2/7
  Time: 13:01
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
</head>
<body>
    <%@include file="header.jsp"%>
    <div style="height: 800px"></div>
    <%@include file="foot.jsp"%>
</body>
</html>

<%@ taglib uri="uri" prefix="prefixOfTag" %>

<%--
  Created by IntelliJ IDEA.
  User: zhaoss-msb
  Date: 2023/2/6
  Time: 22:30
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" isErrorPage="true" %>
<html>
<head>
    <title>Title</title>
</head>
<body>
  现在服务器繁忙，请联系管理员！

<%
    String message = exception.getMessage();
%>
  当前页面的错误是：<%=message%>
</body>
</html>

<%--
  Created by IntelliJ IDEA.
  User: zhaoss-msb
  Date: 2023/2/7
  Time: 14:23
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" errorPage="error.jsp" %>
<html>
<head>
    <title>Title</title>
</head>
<body>
  hello jsp05...
  <%
    int a = 1/0;
  %>
</body>
</html>

<%--
  Created by IntelliJ IDEA.
  User: zhaoss-msb
  Date: 2023/2/7
  Time: 14:48
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
</head>
<body>
    <%
        pageContext.setAttribute("page","hello");
    %>
<%=pageContext.getAttribute("page")%>
</body>
</html>

package com.msb.testservlet;

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.io.IOException;

/**
 * @Author: zhaoss
 */
@WebServlet("/servlet01")
public class Servlet01 extends HttpServlet {
    @Override
    protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        // 通过request作用域存储数据：
        req.setAttribute("reqmsg","hirequest");
        // 请求转发：
        req.getRequestDispatcher("testreq.jsp").forward(req,resp);
    }
}

<%--
  Created by IntelliJ IDEA.
  User: zhaoss-msb
  Date: 2023/2/7
  Time: 14:54
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
</head>
<body>
  <%=request.getAttribute("reqmsg")%>
</body>
</html>

package com.msb.testservlet;

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.io.IOException;

/**
 * @Author: zhaoss
 */
@WebServlet("/servlet02")
public class Servlet02 extends HttpServlet {
    @Override
    protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        // 利用session作用域来存储数据：
        req.getSession().setAttribute("sessionmsg","testsession");
    }
}

<%--
  Created by IntelliJ IDEA.
  User: zhaoss-msb
  Date: 2023/2/7
  Time: 15:00
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
</head>
<body>
    <%=session.getAttribute("sessionmsg")%>
</body>
</html>

package com.msb.testservlet;

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.io.IOException;

/**
 * @Author: zhaoss
 */
@WebServlet("/servlet03")
public class Servlet03 extends HttpServlet {
    @Override
    protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        // 将数据存储在application作用域中：
        req.getServletContext().setAttribute("appmsg","testapp");
    }
}

<%--
  Created by IntelliJ IDEA.
  User: zhaoss-msb
  Date: 2023/2/7
  Time: 15:03
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
</head>
<body>
  <%=application.getAttribute("appmsg")%>
</body>
</html>

${expression}

<%
    pageContext.setAttribute("uname","zhangsan"); // page作用域
    request.setAttribute("uname","lisi"); // request作用域
    session.setAttribute("uname","wangwu"); // session作用域
    application.setAttribute("uname","zaholiu"); // application
%>

<%-- 获取域对象中的数据：默认查找方式为从小到大，找到即止。若四个范围都未找到，则返回空字符串。--%>
${uname} <!-- 输出结果为：zhangsan -->

${pageScope.uname} 			<!-- page作用域 -->
${requestScope.uname} 		<!-- request作用域 -->
${sessionScope.uname} 		<!-- session作用域 -->
${applicationScope.uname} 	<!-- application作用域 -->

<%--
  Created by IntelliJ IDEA.
  User: zhaoss-msb
  Date: 2023/2/7
  Time: 16:22
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
</head>
<body>
    <%
        pageContext.setAttribute("uname","lulu");
        request.setAttribute("uname","lili");
        session.setAttribute("uname","feifei");
        application.setAttribute("uname","mingming");
    %>
    <%--
    下面的用小脚本取出数据就是之前的写法
    如果数据没有取出，显示的效果为：null
    --%>
    <%=pageContext.getAttribute("uname3")%>
    <%--
    下面是el表达式的写法，明显感受到代码简化
    --%>
    ${uname}
    <%--如果数据没有取出，那么展示的就是空白的效果，实际取出的就是空字符串--%>
    ${uname3}
    <br> <%--加入换行标签，发现html标签和el表达式可以一起使用，很方便--%>
    <%--
     使用EL表达式获取域数据的时候，如果没有指明作用域，那会按照作用域由小到大的顺序去找，直到找到为止：
	pageContext ---> request ---> session ---> application
    --%>
    <%--如果我就想要在指定的域中取出数据怎么办呢？
    那么就需要从域对象对应的空间对象中取出数据--%>
    ${sessionScope.uname}
</body>
</html>

<%
	List<String> list = new ArrayList<String>();
	list.add("aaa");
	list.add("bbb");
	list.add("ccc");
	request.setAttribute("list", list);
%>
<%--
    获取List中指定下标的数据
        ${list[下标] }
	获取集合的长度
		${list.size()}
	注：
       list代表的是存在域对象中的变量名（限域变量名）
--%>
${list[1] }

<%
    Map map = new HashMap();
    map.put("aaa", "111");
    map.put("bbb", 2222);
    map.put("ccc-a", 333);
    request.setAttribute("map", map);
%>
<%--
    获取Map中指定值
       ${map["key"] } 或 ${map.key }
	注：
		map代表的是存在域对象中的变量名（限域变量名）
--%>
${map.aaa }
${map["bbb"]}

public class User {

    private Integer userId;
    private String uname;
    private String upwd;

    public Integer getUserId() {
        return userId;
    }

    public void setUserId(Integer userId) {
        this.userId = userId;
    }

    public String getUname() {
        return uname;
    }

    public void setUname(String uname) {
        this.uname = uname;
    }

    public String getUpwd() {
        return upwd;
    }

    public void setUpwd(String upwd) {
        this.upwd = upwd;
    }
}

<%
    User user = new User();
    user.setUserId(1);
    user.setUname("zhangsan");
    user.setUpwd("123456");
    request.setAttribute("user",user);
%>
<%-- JavBean中的属性字段需要提供get方法 --%>
${user} <%-- 获取对象 --%>
${user.uname} <%--获取对象中的属性--%>

<%@ page import="java.util.List" %>
<%@ page import="java.util.ArrayList" %>
<%@ page import="java.util.HashMap" %>
<%@ page import="java.util.Map" %>
<%@ page import="com.msb.pojo.User" %><%--
  Created by IntelliJ IDEA.
  User: zhaoss-msb
  Date: 2023/2/7
  Time: 17:13
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
</head>
<body>
  <%
    // 创建List集合：
    List<String> list = new ArrayList<String>();
    list.add("aaa");
    list.add("bbb");
    list.add("ccc");
    // 将list对象存入request作用域中：
    request.setAttribute("list",list);

    // 创建Map:
    Map map = new HashMap();
    map.put("a","111");
    map.put("b","222");
    map.put("c","333");
    // 将map对象存入request作用域中：
    request.setAttribute("map",map);
    // 创建User的对象：
    User user = new User(1,"xiaoming","123456");
    // 将user对象存入request作用域中：
    request.setAttribute("user",user);
  %>

  <%--利用el表达式获取List中数据--%>
  获取List对象的长度：${list.size()}
  获取List对象指定索引位置的数据：${list[1]}
  <%--利用el表达式获取Map中数据--%>
  获取Map对象中的内容，通过键取出对应的值：${map.b}  ${map["b"]}
  <%--利用el表达式获取User中数据--%>
  获取User对象中的内容：${user}  ----  ${user.pwd}
</body>
</html>

<%--
    加法： +  只有运算操作，没有字符串拼接操作
    减法： -
    乘法： *
    除法：	/ 或 div
--%>
${1 + 1 }
${1 + "1" }
${"1" + "1" }
${"1aaa" + "1" }
${1 / 1 } 或 ${1 div 1 }

<%--
    比较两个值是否相等，返回true或false
    	==  或  eq
--%>
${"a" == "b" }
${"a" eq "d" }

<%--
	大于：>
    小于：<
    大于等于：>=
    小于等于：<=
--%>
${a > b}
${a + 1 > 10 }
${a + b >= 10 }
${a > b && b > 5 }
${a + b > 10 || a - b > 5 }

<%--
    empty
    	判断域对象是否为空。为空，返回true；不为空返回false；注意：字符串对象、集合对象、普通对象的empty测试
    		${empty 限域变量名 }
		判断对象是否不为空。
			${!empty 限域变量名 }
--%>
${empty uname}
${empty list}
${empty map}
${empty user}

<%@ page import="java.util.List" %>
<%@ page import="java.util.ArrayList" %>
<%@ page import="com.msb.pojo.User" %><%--
  Created by IntelliJ IDEA.
  User: zhaoss-msb
  Date: 2023/2/7
  Time: 21:03
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
</head>
<body>
    ${1 + 1}
    ${1 + "1"}
    ${"1" + "1"}
    <%--${"1aaa" + "1"} 直接报错--%>
    ${1 == 1}
    ${1 eq 2}

    <%
        // 存储字符串
        request.setAttribute("a","str");
        request.setAttribute("b","");
        request.setAttribute("c",null);
        // 存储集合：
        List list1 = new ArrayList();
        List list2 = new ArrayList();
        list2.add("aaa");
        List list3 = null;
        request.setAttribute("list1",list1);
        request.setAttribute("list2",list2);
        request.setAttribute("list3",list3);

        User user1 = new User();
        User user2 = new User(1,"lili","123123");
        User user3 = null;
        request.setAttribute("user1",user1);
        request.setAttribute("user2",user2);
        request.setAttribute("user3",user3);


    %>
    <%--
        如果域对象中的数据是字符串：
            存在字符串对象：false
            空字符串：true
            null:true
            不存在的对象：true
    --%>
    <br>
    ${empty a}
    ${empty b}
    ${empty c}
    ${empty d}

    <br>
    <%--
        对于集合对象来说，如果集合里面的元素为0：true
        对于集合对象来说，如果集合里面的元素>0：false
        集合是null：true
    --%>
    ${empty list1}
    ${empty list2}
    ${empty list3}

    <%--对于普通对象来说，只要创建了对象就不是空--%>
    <br>
    ${empty user1}
    ${empty user2}
    ${empty user3}
</body>
</html>

1. **核心标签库**
        	2. SQL标签库
     	3. 函数标签库
            	4. **格式化标签库**
           	5.  XML标签库

<%@taglib uri="" prefix="" %>

<%@taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %>

<c:if test="<boolean>" var="<string>" scope="<string>">
   ...
</c:if>

<%--
  Created by IntelliJ IDEA.
  User: zhaoss-msb
  Date: 2023/2/7
  Time: 23:16
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<%@taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core"%>
<html>
<head>
    <title>Title</title>
</head>
<body>
    <%
        // 在request作用域中存储数据：
        // 存储int类型数据，学生的成绩：
        request.setAttribute("score",95);
    %>

    <%--如果成绩在60分以上，就是及格：--%>
    <c:if test="${score >= 60}">
        成绩及格！！
    </c:if>
    <c:if test="${score < 60}">
        成绩不及格！！
    </c:if>
    

    <%--练习var scope属性：
        var:接收test表达式的结果
        scope:代表var变量的作用域
     --%>
    <c:if test="${score >= 60}" var="flag" scope="request">
        <%--服务器的跳转：类似之前学习的请求转发--%>
        <jsp:forward page="index.jsp"></jsp:forward>
        成绩及格！！${flag}
    </c:if>
</body>
</html>

<c:choose>
    <c:when test="<boolean>">
        ...
    </c:when>
    <c:when test="<boolean>">
        ...
    </c:when>
    ...
    ...
    <c:otherwise>
        ...
    </c:otherwise>
</c:choose>

<%--
  Created by IntelliJ IDEA.
  User: zhaoss-msb
  Date: 2023/2/7
  Time: 23:16
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<%@taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core"%>
<html>
<head>
    <title>Title</title>
</head>
<body>
    <%
        // 在request作用域中存储数据：
        // 存储int类型数据，学生的成绩：
        request.setAttribute("score",95);
    %>
   
    <c:choose>
        <c:when test="${score >= 90}">
            成绩属于A级别。
        </c:when>
        <c:when test="${score >= 80 && score < 90}">
            成绩属于B级别。
        </c:when>
        <c:when test="${score >= 70 && score < 80}">
            成绩属于C级别。
        </c:when>
        <c:when test="${score >= 60 && score < 70}">
            成绩属于D级别。
        </c:when>
        <c:otherwise>
            成绩属于E级别。
        </c:otherwise>
    </c:choose>
    
</body>
</html>

<c:forEach
    items="<object>"
    begin="<int>"
    end="<int>"
    step="<int>"
    var="<string>"
</c:forEach>

<c:forEach var="限域变量名" begin="开始数" end="结束数" step="迭代数" >

</c:forEach>

相当于java的for循环：

for(int i = 0; i < 10; i++) {

}

<%@ page import="java.util.ArrayList" %>
<%@ page import="java.util.List" %>
<%@ page import="java.util.HashMap" %>
<%@ page import="java.util.Map" %><%--
  Created by IntelliJ IDEA.
  User: zhaoss-msb
  Date: 2023/2/8
  Time: 14:33
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<%@taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core"%>
<html>
<head>
    <title>Title</title>
</head>
<body>
  <%--输出0-10--%>
  <c:forEach var="i" begin="0" end="10">
    ${i}
  </c:forEach>
  <hr>
  <%--输出0,2,4,6,8,10--%>
  <c:forEach var="i" begin="0" end="10" step="2">
    ${i}
  </c:forEach>
</body>
</html>

<c:forEach items="被循环的集合" var="限域变量名">
					
</c:forEach>

相当于java的foreach循环：

for(String str : list) {

}

<%@ page import="java.util.ArrayList" %>
<%@ page import="java.util.List" %>
<%@ page import="java.util.HashMap" %>
<%@ page import="java.util.Map" %><%--
  Created by IntelliJ IDEA.
  User: zhaoss-msb
  Date: 2023/2/8
  Time: 14:33
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<%@taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core"%>
<html>
<head>
    <title>Title</title>
</head>
<body>
  <%
    // 存储字符串
    request.setAttribute("str","java,html,js,jsp");
    request.setAttribute("str2","java#html#js#jsp");
    String[] str3 = {"java","css","servlet"};
    request.setAttribute("str3",str3);
    List<String> list = new ArrayList<>();
    list.add("aaa");
    list.add("bbb");
    list.add("ccc");
    request.setAttribute("list",list);
    Map map = new HashMap<>();
    map.put("a","1111");
    map.put("b","2222");
    map.put("c","3333");
    request.setAttribute("map",map);
  %>
  遍历字符串(拼接的符号是逗号)：
  <c:forEach items="${str}" var="i">
    ${i}--->
  </c:forEach>
  <hr>
  遍历字符串(拼接的符号是#)：delims表示分隔符号：
  <c:forTokens items="${str2}" delims="#" var="i">
    ${i}--->
  </c:forTokens>
  <hr>
  对数组进行遍历：
  <c:forEach items="${str3}" var="i">
    ${i}--->
  </c:forEach>
  <hr>
  对List集合进行遍历：
  <c:forEach items="${list}" var="i">
    ${i}--->
  </c:forEach>
  <hr>
  对Map集合进行遍历：
  <c:forEach items="${map}" var="i">
    ${i}--->${i.key}--->${i.value}
  </c:forEach>
</body>
</html>

<fmt:formatNumber
  value="<string>"
  type="<string>"
  var="<string>"
  scope="<string>"/>

<%--
  Created by IntelliJ IDEA.
  User: zhaoss-msb
  Date: 2023/2/8
  Time: 15:18
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<%@taglib prefix="fmt" uri="http://java.sun.com/jsp/jstl/fmt"%>
<html>
<head>
    <title>Title</title>
</head>
<body>
    <%--
    value:你要处理的数据
    type：数据你要处理为哪种类型
    var：数据用var里面指定的变量做接收
    如果设置了var属性，则格式化后的结果不会输出，需要通过el表达式获取var对应的限域变量名
    如果没有设置var属性，那么就可以自动数据最终结果
    scope:变量作用域：4个作用域--%>
    <fmt:formatNumber value="10" type="number" var="num"/>${num}
    <fmt:formatNumber value="10" type="number"/>
    <fmt:formatNumber value="10" type="percent"/>
    <fmt:formatNumber value="10" type="currency"/>
    <fmt:setLocale value="en_US"/><%--设置时区--%>
    <fmt:formatNumber value="10" type="currency"/>

</body>
</html>

<fmt:formatDate
  value="<string>"
  type="<string>"
  dateStyle="<string>"
  timeStyle="<string>"
  pattern="<string>"
  timeZone="<string>"
  var="<string>"
  scope="<string>"/>

<%@ page import="java.util.Date" %><%--
  Created by IntelliJ IDEA.
  User: zhaoss-msb
  Date: 2023/2/8
  Time: 15:33
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<%@taglib prefix="fmt" uri="http://java.sun.com/jsp/jstl/fmt"%>
<html>
<head>
    <title>Title</title>
</head>
<body>
  <%
    // 在作用域中存储日期：
    request.setAttribute("date",new Date());
  %>
  <%--将日期从作用域中取出：--%>
  ${date}
  <hr>
  <fmt:formatDate value="${date}" pattern="yyyy-MM-dd"/>
  <fmt:formatDate value="${date}" pattern="yyyy年MM月dd日"/>
</body>
</html>

<fmt:parseNumber
  value="<string>"
  type="<string>"
  var="<string>"
  scope="<string>"/>

<fmt:parseNumber value="100"  /> <br>
<fmt:parseNumber value="100"  type="number" /> <br>
<fmt:parseNumber value="100%"  type="percent" /> <br>
<fmt:parseNumber value="￥10.00"  type="currency" /> <br>

<fmt:parseDate
   value="<string>"
   type="<string>"
   dateStyle="<string>"
   timeStyle="<string>"
   pattern="<string>"
   var="<string>"
   scope="<string>"/>

<fmt:parseDate value="2020-01-06" type="date" /> <br>
<fmt:parseDate value="2020/01/06" pattern="yyyy/MM/dd" /> <br>

<%--
  Created by IntelliJ IDEA.
  User: zhaoss-msb
  Date: 2023/2/8
  Time: 21:22
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
</head>
<body>
  <form action="loginServlet" method="post">
    用户名：<input type="text" name="uname"><br>
    密码：<input type="password" name="pwd"><br>
    <input type="submit" value="登录"><br>
    ${failmsg}
  </form>
</body>
</html>

package com.msb.pojo;

/**
 * @Author: zhaoss
 */
public class User {
    private int uid;
    private String uname;
    private String pwd;

    public User(int uid, String uname, String pwd) {
        this.uid = uid;
        this.uname = uname;
        this.pwd = pwd;
    }

    public User() {
    }

    public int getUid() {
        return uid;
    }

    public void setUid(int uid) {
        this.uid = uid;
    }

    public String getUname() {
        return uname;
    }

    public void setUname(String uname) {
        this.uname = uname;
    }

    public String getPwd() {
        return pwd;
    }

    public void setPwd(String pwd) {
        this.pwd = pwd;
    }

    @Override
    public String toString() {
        return "User{" +
                "uid=" + uid +
                ", uname='" + uname + '\'' +
                ", pwd='" + pwd + '\'' +
                '}';
    }
}

package com.msb.servlet;

import com.msb.dao.UserDao;
import com.msb.pojo.User;

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.io.IOException;

/**
 * @Author: zhaoss
 */
@WebServlet("/loginServlet")
public class LoginServlet extends HttpServlet {
    @Override
    protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        // 1. 接收页面传送过来的数据：
        String uname = req.getParameter("uname");
        String pwd = req.getParameter("pwd");
        System.out.println(uname);
        System.out.println(pwd);
        // 2. 连接数据库：
        UserDao userDao = new UserDao();
        User user = userDao.selectOne(uname, pwd);
        System.out.println(user);
        // 3. 根据数据库处理的结果 响应数据：
        if (user != null){// 数据查询到--》用户存在
            // 跳转到项目首页 （重定向）
            resp.sendRedirect(req.getContextPath() + "/index.jsp");
        }else{// 数据没有查询到---》用户不存在
            // 登录错误的提示信息数据存储在request作用域中：
            req.setAttribute("failmsg","登录失败");
            // 请求转发：
            req.getRequestDispatcher("/login.jsp").forward(req,resp);
        }
    }
}

package com.msb.dao;

import com.msb.pojo.User;

import java.sql.*;

/**
 * @Author: zhaoss
 */
public class UserDao {
    // 查询学生信息：
    public User selectOne(String uname,String pwd){
        User user = null;
        Connection conn = null;
        PreparedStatement ps = null;
        ResultSet rs = null;
        try {
            // 加载驱动：
            Class.forName("com.mysql.cj.jdbc.Driver");
            // 获取连接：
            conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/logintest?useUnicode=true&characterEncoding=utf-8&useSSL=false&serverTimezone=GMT%2B8&allowPublicKeyRetrieval=true","root","root");
            // 创建会话：
            ps = conn.prepareStatement("select * from t_user where uname = ? and pwd = ?");
            // 给问号设置数值：
            ps.setString(1,uname);
            ps.setString(2,pwd);
            // 进行查询：
            rs = ps.executeQuery();
            // 处理结果集：
            if(rs.next()){
                int uid = rs.getInt("uid");
                String username = rs.getString("uname");
                String password = rs.getString("pwd");
                // 将数据封装为对象：
                user = new User(uid,username,password);
            }
        } catch (ClassNotFoundException e) {
            throw new RuntimeException(e);
        } catch (SQLException e) {
            throw new RuntimeException(e);
        } finally {
            // 数据库资源关闭：
            try {
                rs.close();
            } catch (SQLException e) {
                throw new RuntimeException(e);
            }
            try {
                ps.close();
            } catch (SQLException e) {
                throw new RuntimeException(e);
            }
            try {
                conn.close();
            } catch (SQLException e) {
                throw new RuntimeException(e);
            }
        }

        return user;
    }
}

<%--
  Created by IntelliJ IDEA.
  User: zhaoss-msb
  Date: 2023/2/8
  Time: 21:22
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
</head>
<body>
  <form action="loginServlet" method="post">
    用户名：<input type="text" name="uname"><br>
    密码：<input type="password" name="pwd"><br>
    <input type="submit" value="登录"><br>
    ${failmsg}
  </form>
</body>
</html>

<%--
  Created by IntelliJ IDEA.
  User: zhaoss-msb
  Date: 2023/2/13
  Time: 14:04
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
  <head>
    <title>$Title$</title>
  </head>
  <body>
  项目首页，登录成功。
  </body>
</html>

package com.msb.pojo;

/**
 * @Author: zhaoss
 */
public class User {
    private int uid;
    private String uname;
    private String pwd;

    public User(int uid, String uname, String pwd) {
        this.uid = uid;
        this.uname = uname;
        this.pwd = pwd;
    }

    public User() {
    }

    public int getUid() {
        return uid;
    }

    public void setUid(int uid) {
        this.uid = uid;
    }

    public String getUname() {
        return uname;
    }

    public void setUname(String uname) {
        this.uname = uname;
    }

    public String getPwd() {
        return pwd;
    }

    public void setPwd(String pwd) {
        this.pwd = pwd;
    }

    @Override
    public String toString() {
        return "User{" +
                "uid=" + uid +
                ", uname='" + uname + '\'' +
                ", pwd='" + pwd + '\'' +
                '}';
    }
}

package com.msb.controller;

import com.msb.dao.UserDao;
import com.msb.pojo.User;
import com.msb.service.UserService;
import com.msb.service.impl.UserServiceImpl;

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.io.IOException;

/**
 * @Author: zhaoss
 */
@WebServlet("/loginServlet")
public class LoginServlet extends HttpServlet {
    UserService userService = new UserServiceImpl();
    @Override
    protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        // 1. 接收页面传送过来的数据：
        String uname = req.getParameter("uname");
        String pwd = req.getParameter("pwd");
        System.out.println(uname);
        System.out.println(pwd);
        // 2. 调用业务层：：
        User user = userService.selectUserInfo(uname, pwd);
        System.out.println(user);
        // 3. 根据数据库处理的结果 响应数据：
        if (user != null){// 数据查询到--》用户存在
            // 跳转到项目首页 （重定向）
            resp.sendRedirect(req.getContextPath() + "/index.jsp");
        }else{// 数据没有查询到---》用户不存在
            // 登录错误的提示信息数据存储在request作用域中：
            req.setAttribute("failmsg","登录失败");
            // 请求转发：
            req.getRequestDispatcher("/login.jsp").forward(req,resp);
        }
    }
}

package com.msb.service;

import com.msb.pojo.User;

/**
 * @Author: zhaoss
 */
public interface UserService {
    // 根据用户名和密码查询用户信息：
    public abstract User selectUserInfo(String uname,String pwd);
}

package com.msb.service.impl;

import com.msb.dao.UserDao;
import com.msb.dao.impl.UserDaoImpl;
import com.msb.pojo.User;
import com.msb.service.UserService;

/**
 * @Author: zhaoss
 */
public class UserServiceImpl implements UserService {
    UserDao userDao = new UserDaoImpl();

    @Override
    public User selectUserInfo(String uname, String pwd) {
        return userDao.selectOneUser(uname,pwd);
    }

}

package com.msb.dao;

import com.msb.pojo.User;

/**
 * @Author: zhaoss
 */
public interface UserDao {
    // 根据用户名和密码查询用户信息：
    public abstract User selectOneUser(String uname, String pwd);
}

package com.msb.dao.impl;

import com.msb.dao.UserDao;
import com.msb.pojo.User;

import java.sql.*;

/**
 * @Author: zhaoss
 */
public class UserDaoImpl implements UserDao {
    @Override
    public User selectOneUser(String uname, String pwd) {
        User user = null;
        Connection conn = null;
        PreparedStatement ps = null;
        ResultSet rs = null;
        try {
            // 加载驱动：
            Class.forName("com.mysql.cj.jdbc.Driver");
            // 获取连接：
            conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/logintest?useUnicode=true&characterEncoding=utf-8&useSSL=false&serverTimezone=GMT%2B8&allowPublicKeyRetrieval=true","root","root");
            // 创建会话：
            ps = conn.prepareStatement("select * from t_user where uname = ? and pwd = ?");
            // 给问号设置数值：
            ps.setString(1,uname);
            ps.setString(2,pwd);
            // 进行查询：
            rs = ps.executeQuery();
            // 处理结果集：
            if(rs.next()){
                int uid = rs.getInt("uid");
                String username = rs.getString("uname");
                String password = rs.getString("pwd");
                // 将数据封装为对象：
                user = new User(uid,username,password);
            }
        } catch (ClassNotFoundException e) {
            throw new RuntimeException(e);
        } catch (SQLException e) {
            throw new RuntimeException(e);
        } finally {
            // 数据库资源关闭：
            try {
                rs.close();
            } catch (SQLException e) {
                throw new RuntimeException(e);
            }
            try {
                ps.close();
            } catch (SQLException e) {
                throw new RuntimeException(e);
            }
            try {
                conn.close();
            } catch (SQLException e) {
                throw new RuntimeException(e);
            }
        }

        return user;
    }
}

package com.msb.controller;

import com.msb.dao.UserDao;
import com.msb.pojo.User;
import com.msb.service.UserService;
import com.msb.service.impl.UserServiceImpl;

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.io.IOException;

/**
 * @Author: zhaoss
 */
@WebServlet("/loginServlet")
public class LoginServlet extends HttpServlet {
    UserService userService = new UserServiceImpl();
    @Override
    protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        // 1. 接收页面传送过来的数据：
        String uname = req.getParameter("uname");
        String pwd = req.getParameter("pwd");
        System.out.println(uname);
        System.out.println(pwd);
        // 2. 调用业务层：：
        User user = userService.selectUserInfo(uname, pwd);
        System.out.println(user);
        // 3. 根据数据库处理的结果 响应数据：
        if (user != null){// 数据查询到--》用户存在
            // 一旦有这个用户，登录成功，将用户信息存在session作用域中：
            req.getSession().setAttribute("user",user);//存储对象
            // 跳转到项目首页 （重定向）
            resp.sendRedirect(req.getContextPath() + "/index.jsp");
        }else{// 数据没有查询到---》用户不存在
            // 登录错误的提示信息数据存储在request作用域中：
            req.setAttribute("failmsg","登录失败");
            // 请求转发：
            req.getRequestDispatcher("/login.jsp").forward(req,resp);
        }
    }
}

package com.msb.filter;

import com.msb.pojo.User;

import javax.servlet.*;
import javax.servlet.annotation.WebFilter;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

/**
 * @Author: zhaoss
 */
@WebFilter("/*") //1.首先先将所有的资源都进行拦截
public class LoginFilter implements Filter {
    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
        Filter.super.init(filterConfig);
    }

    @Override
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
        // 3.基于HTTP的请求的对象：
        HttpServletRequest request = (HttpServletRequest) servletRequest;
        HttpServletResponse response = (HttpServletResponse) servletResponse;
        // 4.在完成2,3步骤以后，登录index.jsp页面后出现问题： 将您重定向的次数过多。
        // 5.所以我们要做的事就是设置放行资源-登录页面：
        // 6.通过地址栏请求的地址判断是否携带login.jsp,如果携带的话，那么直接放行：
        String uri = request.getRequestURI();
        if (uri.contains("/login.jsp")){
            // 7.如果携带了/login.jsp，就将资源进行放行操作：
            filterChain.doFilter(request,response);
            return;
        }
        // 8. 对静态资源进行放行，否则登录页面中使用的图片、css、js的内容都无法访问：
        if (uri.contains("/images")){
            filterChain.doFilter(request,response);
            return;
        }
        // 8.2 在登录页面点击登录以后，会访问LoginServlet,所以也要对LoginServlet进行放行：
        if (uri.contains("/loginServlet")){
            filterChain.doFilter(request,response);
            return;
        }
        // 9.完成到第8步已经可以拦截非法操作了，但是如果登录以后，还访问index.jsp是不可以的
        // 10. 如果已经登录了，就创建了会话了，那么就可以随意的访问其他页面了
        User user = (User)request.getSession().getAttribute("user");
        if (user != null){// 11.如果用户不是空，证明已经登录成功，那么就放行
            filterChain.doFilter(request,response);
            return;
        }
        // 2.只要进行了非法访问，就跳转到登录页面：（重定向）
        response.sendRedirect("login.jsp");
    }

    @Override
    public void destroy() {
        Filter.super.destroy();
    }
}