JSP之JSTL_functions

<?xml version="1.0" encoding="UTF-8" ?>

<taglib xmlns="http://java.sun.com/xml/ns/j2ee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-jsptaglibrary_2_0.xsd" version="2.0">

<description>JSTL 1.1 functions library</description>
<display-name>JSTL functions</display-name>
<tlib-version>1.1</tlib-version>
<short-name>fn</short-name>
<uri>http://java.sun.com/jsp/jstl/functions</uri>

<function>
<description>
Tests if an input string contains the specified substring.
</description>
<name>contains</name>
<function-class>org.apache.taglibs.standard.functions.Functions</function-class>
<function-signature>boolean contains(java.lang.String, java.lang.String)</function-signature>
<example>
<c:if test="${fn:contains(name, searchString)}">
</example>
</function>

<function>
<description>
Tests if an input string contains the specified substring in a case insensitive way.
</description>
<name>containsIgnoreCase</name>
<function-class>org.apache.taglibs.standard.functions.Functions</function-class>
<function-signature>boolean containsIgnoreCase(java.lang.String, java.lang.String)</function-signature>
<example>
<c:if test="${fn:containsIgnoreCase(name, searchString)}">
</example>
</function>

<function>
<description>
Tests if an input string ends with the specified suffix.
</description>
<name>endsWith</name>
<function-class>org.apache.taglibs.standard.functions.Functions</function-class>
<function-signature>boolean endsWith(java.lang.String, java.lang.String)</function-signature>
<example>
<c:if test="${fn:endsWith(filename, ".txt")}">
</example>
</function>

<function>
<description>
Escapes characters that could be interpreted as XML markup.
</description>
<name>escapeXml</name>
<function-class>org.apache.taglibs.standard.functions.Functions</function-class>
<function-signature>java.lang.String escapeXml(java.lang.String)</function-signature>
<example>
${fn:escapeXml(param:info)}
</example>
</function>

<function>
<description>
Returns the index withing a string of the first occurrence of a specified substring.
</description>
<name>indexOf</name>
<function-class>org.apache.taglibs.standard.functions.Functions</function-class>
<function-signature>int indexOf(java.lang.String, java.lang.String)</function-signature>
<example>
${fn:indexOf(name, "-")}
</example>
</function>

<function>
<description>
Joins all elements of an array into a string.
</description>
<name>join</name>
<function-class>org.apache.taglibs.standard.functions.Functions</function-class>
<function-signature>java.lang.String join(java.lang.String[], java.lang.String)</function-signature>
<example>
${fn:join(array, ";")}
</example>
</function>

<function>
<description>
Returns the number of items in a collection, or the number of characters in a string.
</description>
<name>length</name>
<function-class>org.apache.taglibs.standard.functions.Functions</function-class>
<function-signature>int length(java.lang.Object)</function-signature>
<example>
You have ${fn:length(shoppingCart.products)} in your shopping cart.
</example>
</function>

<function>
<description>
Returns a string resulting from replacing in an input string all occurrences
of a "before" string into an "after" substring.
</description>
<name>replace</name>
<function-class>org.apache.taglibs.standard.functions.Functions</function-class>
<function-signature>java.lang.String replace(java.lang.String, java.lang.String, java.lang.String)</function-signature>
<example>
${fn:replace(text, "-", "•")}
</example>
</function>

<function>
<description>
Splits a string into an array of substrings.
</description>
<name>split</name>
<function-class>org.apache.taglibs.standard.functions.Functions</function-class>
<function-signature>java.lang.String[] split(java.lang.String, java.lang.String)</function-signature>
<example>
${fn:split(customerNames, ";")}
</example>
</function>

<function>
<description>
Tests if an input string starts with the specified prefix.
</description>
<name>startsWith</name>
<function-class>org.apache.taglibs.standard.functions.Functions</function-class>
<function-signature>boolean startsWith(java.lang.String, java.lang.String)</function-signature>
<example>
<c:if test="${fn:startsWith(product.id, "100-")}">
</example>
</function>

<function>
<description>
Returns a subset of a string.
</description>
<name>substring</name>
<function-class>org.apache.taglibs.standard.functions.Functions</function-class>
<function-signature>java.lang.String substring(java.lang.String, int, int)</function-signature>
<example>
P.O. Box: ${fn:substring(zip, 6, -1)}
</example>
</function>

<function>
<description>
Returns a subset of a string following a specific substring.
</description>
<name>substringAfter</name>
<function-class>org.apache.taglibs.standard.functions.Functions</function-class>
<function-signature>java.lang.String substringAfter(java.lang.String, java.lang.String)</function-signature>
<example>
P.O. Box: ${fn:substringAfter(zip, "-")}
</example>
</function>

<function>
<description>
Returns a subset of a string before a specific substring.
</description>
<name>substringBefore</name>
<function-class>org.apache.taglibs.standard.functions.Functions</function-class>
<function-signature>java.lang.String substringBefore(java.lang.String, java.lang.String)</function-signature>
<example>
Zip (without P.O. Box): ${fn:substringBefore(zip, "-")}
</example>
</function>

<function>
<description>
Converts all of the characters of a string to lower case.
</description>
<name>toLowerCase</name>
<function-class>org.apache.taglibs.standard.functions.Functions</function-class>
<function-signature>java.lang.String toLowerCase(java.lang.String)</function-signature>
<example>
Product name: ${fn:toLowerCase(product.name)}
</example>
</function>

<function>
<description>
Converts all of the characters of a string to upper case.
</description>
<name>toUpperCase</name>
<function-class>org.apache.taglibs.standard.functions.Functions</function-class>
<function-signature>java.lang.String toUpperCase(java.lang.String)</function-signature>
<example>
Product name: ${fn:UpperCase(product.name)}
</example>
</function>

<function>
<description>
Removes white spaces from both ends of a string.
</description>
<name>trim</name>
<function-class>org.apache.taglibs.standard.functions.Functions</function-class>
<function-signature>java.lang.String trim(java.lang.String)</function-signature>
<example>
Name: ${fn:trim(name)}
</example>
</function>

</taglib>

上述是http://java.sun.com/jsp/jstl/functions的源代码

用来弥补JSTL在处理字符串上的缺陷

使用的方式

一、

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

二、

在WEB-INF目录下创建functions.ltd

然后将上述代码拷进去

<%@ taglib prefix="fn" uri="/WEB-INF/functions.tld" %>

或则

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

区别在于说这样的话即使不联网也可以使用

<!-- 函数说明 -->

函数名	函数说明	使用举例
fn:contains	判断字符串是否包含另外一个字符串	<c:if test="${fn:contains(name, searchString)}">
fn:containsIgnoreCase	判断字符串是否包含另外一个字符串(大小写无关)	<c:if test="${fn:containsIgnoreCase(name, searchString)}">
fn:endsWith	判断字符串是否以另外字符串结束	<c:if test="${fn:endsWith(filename, ".txt")}">
fn:escapeXml	把一些字符转成XML表示，例如<字符应该转为<	${fn:escapeXml(param:info)}
fn:indexOf	子字符串在母字符串中出现的位置	${fn:indexOf(name, "-")}
fn:join	将数组中的数据联合成一个新字符串，并使用指定字符格开	${fn:join(array, ";")}
fn:length	获取字符串的长度，或者数组的大小	${fn:length(shoppingCart.products)}
fn:replace	替换字符串中指定的字符	${fn:replace(text, "-", "•")}
fn:split	把字符串按照指定字符切分	${fn:split(customerNames, ";")}
fn:startsWith	判断字符串是否以某个子串开始	<c:if test="${fn:startsWith(product.id, "100-")}">
fn:substring	获取子串	${fn:substring(zip, 6, -1)}
fn:substringAfter	获取从某个字符所在位置开始的子串	${fn:substringAfter(zip, "-")}
fn:substringBefore	获取从开始到某个字符所在位置的子串	${fn:substringBefore(zip, "-")}
fn:toLowerCase	转为小写	${fn.toLowerCase(product.name)}
fn:toUpperCase	转为大写字符	${fn.UpperCase(product.name)}
fn:trim	去除字符串前后的空格	${fn.trim(name)}

其实就是一些JAVA中处理字符串的方法。

end..