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>
      &lt;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>
      &lt;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>
      &lt;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>
      &lt;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>

使用方法

---

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

---

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&lt;   ${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)}