当前位置：网站首页>JSP El expression, JSTL tag

JSP El expression, JSTL tag

2022-07-27 16:59:00 【Not very [email protected]】

Catalog

1、EL expression

2、JSTL Tag library （ Example of core label ）

1、web Introduce... Into the project jstl Tag library dependency

2、 In the use of jstl Labeled jsp Introduce the tag library on the web page

3、 Application, for example,

3.1、c:foreach label

3.2、c:if label

1、EL expression

--> effect : Get the data in the four domain objects .

grammar : ${xxxScope.key}

We originally passed xxx.getAttribute(key) You can also get the data in the four domains , Why even use EL expression , because EL Expression syntax is more concise .
And later we can Of jstl Tag library . If EL Expression not found for key, Returns an empty string "".
EL Expression belongs to jsp Or explain later thymeleaf The grammar of

<%@ page import="entity.Student" %>
<%@ page import="java.util.ArrayList" %><%--
  Created by IntelliJ IDEA.
  User: Administrator
  Date: 2022/5/16
  Time: 14:41
  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>
  <%
    pageContext.setAttribute("name","page");
    request.setAttribute("name","request");
    session.setAttribute("name","session");
    application.setAttribute("name","application");

  %>
  ${pageScope.name}
  ${requestScope.name}
  ${sessionScope.name}
  ${applicationScope.name}

 


  </body>
</html>

el expression You can also omit scope ${key} Which object will it get data from . Default
from pageContext Is the scan right key, If so, don't continue scanning , If
If not, continue scanning request, And so on .

 Do not specify a range <br>
 ${name}<br> 
 ${name}<br> 
 ${name}<br> 
 ${name}<br>

2、JSTL Tag library （ Example of core label ）

There are some commonly used labels --- such as : Circular label Judgment labels .
The purpose of using these labels is to reduce jsp in java Add script code . Enterprises do not recommend large
Home in jsp Too many <%%> This will make the web page more messy . At this time, someone provided
JSTL Tag library .

How to use jstl Tag library :

1、web Introduce... Into the project jstl Tag library dependency

2、 In the use of jstl Labeled jsp Introduce the tag library on the web page

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

3、 Application, for example,

3.1、c:foreach label

<%@ page import="entity.Student" %>
<%@ page import="java.util.ArrayList" %><%--
  Created by IntelliJ IDEA.
  User: Administrator
  Date: 2022/5/16
  Time: 14:41
  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>
  <%
    ArrayList<Student> students = new ArrayList<>();
    students.add(new Student("lwh",2,1));
    students.add(new Student("bzd",2,0));
    students.add(new Student("flj",2,1));
    students.add(new Student("wsl",2,0));
    request.setAttribute("u",students);

  %>
  <table border="1" width="500">
    <tr>
      <th> full name </th>
      <th> Age </th>
      <th> Gender </th>
    </tr>
    <c:forEach items="${requestScope.u}" var="student">
      <tr>
        <td>${student.name}</td>
        <td>${student.age}</td>
        <td>${student.gender}</td>
      </tr>
    </c:forEach>
  </table>


  </body>
</html>

3.2、c:if label


<%@ page import="entity.Student" %>
<%@ page import="java.util.ArrayList" %>
<%@ 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>
  <%
    ArrayList<Student> students = new ArrayList<>();
    students.add(new Student("lwh",2,1));
    students.add(new Student("bzd",2,0));
    students.add(new Student("flj",2,1));
    students.add(new Student("wsl",2,0));
    request.setAttribute("u",students);

  %>
  <table border="1" width="500">
    <tr>
      <th> full name </th>
      <th> Age </th>
      <th> Gender </th>
    </tr>
    <c:forEach items="${requestScope.u}" var="student">
      <tr>
        <td>${student.name}</td>
        <td>${student.age}</td>
        <td>${student.gender}</td>

        <c:if test="${student.age>=15}">
              <td> Young people </td>
        </c:if>
        <c:if test="${student.age<15}">
              <td> Primary school students </td>
        </c:if>

      </tr>
    </c:forEach>
  </table>


  </body>
</html>

原网站

版权声明
本文为[Not very [email protected]]所创，转载请带上原文链接，感谢
https://yzsam.com/2022/208/202207271449228147.html