<x:choose>, <x:when>, <x:otherwise> 标签

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2023-12-01

JSP 标准标签库

<x:choose>标签与Java switch语句有相同的功能。switch语句有case语句，而<x:choose>标签有<x:when>标签。switch语句有default语句，而<x:choose>标签有<x:otherwise>标签。

语法格式

<x:choose>
 <x:when select="<string>">
     ...
 </x:when>
 <x:when select="<string>">
     ...
 </x:when>
     ...
     ...
 <x:otherwise>
     ...
 </x:otherwise>
</x:choose>

属性

<x:choose>没有属性。
<x:when>的属性在下表中给出。
<x:otherwise>没有属性。

<x:when>标签的属性：

属性	描述	是否必要	默认值
select	条件	是	无

实例演示

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<%@ taglib prefix="x" uri="http://java.sun.com/jsp/jstl/xml" %>

<html>
<head>
  <title>JSTL x:choose 标签</title>
</head>
<body>
<h3>Books Info:</h3>

<c:set var="xmltext">
  <books>
    <book>
      <name>Padam History</name>
      <author>ZARA</author>
      <price>100</price>
    </book>
    <book>
      <name>Great Mistry</name>
      <author>NUHA</author>
      <price>2000</price>
    </book>
  </books>
</c:set>

<x:parse xml="${xmltext}" var="output"/>
<x:choose>
   <x:when select="$output//book/author = 'ZARA'">
      Book is written by ZARA
   </x:when>
   <x:when select="$output//book/author = 'NUHA'">
      Book is written by NUHA
   </x:when>
   <x:otherwise>
      Unknown author.
   </x:otherwise>
</x:choose>

</body>
</html>

运行结果如下：

BOOKS INFO:
Book is written by ZARA

JSP 标准标签库