[java web] Detailed explanation of jsp + el expression + jstl tag library

jsp

You can write java code in html

Essence: servlet

instruction

<%@ page contentType="text/html;charset=UTF-8" errorPage="index.jsp" language="java" %>
<%@include file="login.html" %> <!-- 引进相同的页面  -->
<%@ taglib prefix="" %>  <%--引入标签库--%>

MVC pattern

1.Model: mode, business operation – javaBean

2.View: View, display data – JSP

3.Controller: Controller–Servlet

EL expression

Format

${3 > 4}

\${3 > 4}   <%--忽略el表达式--%>

Get shared data

<%
request.setAttribute("zhangsan","hello");
%>
${requestScope.zhangsan}

JSTL

jsp standard tag library

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

Format

<%
    request.setAttribute("number",3);

%>

<c:if test="${number % 2 != 0}">
    ${number}为奇数
</c:if>

<c:choose>
        <c:when test="${number == 1}">星期一</c:when>
        <c:when test="${number == 2}">星期一</c:when>
        <c:when test="${number == 4}">星期一</c:when>
        <c:when test="${number == 1}">星期一</c:when>
        <c:when test="${number == 1}">星期一</c:when>
        <c:when test="${number == 1}">星期一</c:when>
        <c:when test="${number == 1}">星期一</c:when>
        
        <c:otherwise>....</c:otherwise>
    </c:choose>

<c:forEach begin="1" end="10" var="i" step="1">
        ${i}<br>
    </c:forEach>

<%-- 遍历容器 --%>
<c:forEach items="${list}" var="str" varStatus="s">
        ${s.index} ${s.count} ${str}
    </c:forEach>