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<?xml version="1.0" encoding="ISO-8859-1"?><!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en"> <head> <meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1" /> <meta http-equiv="Content-Style-Type" content="text/css" /> <title>Functions</title> <link rel="StyleSheet" href="document.css" type="text/css" media="all" /> <link rel="StyleSheet" href="catalog.css" type="text/css" media="all" /> <link rel="Table of Contents" href="J2EETutorialTOC.html" /> <link rel="Previous" href="JSTL7.html" /> <link rel="Next" href="JSTL9.html" /> <link rel="Index" href="J2EETutorialIX.html" /> </head> <body> <table width="550" summary="layout" id="SummaryNotReq1"> <tr> <td align="left" valign="center"> <font size="-1"> <a href="http://java.sun.com/j2ee/1.4/download.html#tutorial" target="_blank">Download</a> <br> <a href="http://java.sun.com/j2ee/1.4/docs/tutorial/information/faq.html" target="_blank">FAQ</a> <br> <a href="http://java.sun.com/j2ee/1.4/docs/tutorial/information/history.html" target="_blank">History</a> </td> <td align="center" valign="center"><a accesskey="p" href="JSTL7.html"><img id="LongDescNotReq1" src="images/PrevArrow.gif" width="26" height="26" border="0" alt="Prev" /></a><a accesskey="c" href="J2EETutorialFront.html"><img id="LongDescNotReq1" src="images/UpArrow.gif" width="26" height="26" border="0" alt="Home" /></a><a accesskey="n" href="JSTL9.html"><img id="LongDescNotReq3" src="images/NextArrow.gif" width="26" height="26" border="0" alt="Next" /></a><a accesskey="i" href="J2EETutorialIX.html"></a> </td> <td align="right" valign="center"> <font size="-1"> <a href="http://java.sun.com/j2ee/1.4/docs/api/index.html" target="_blank">API</a> <br> <a href="http://java.sun.com/j2ee/1.4/docs/tutorial/information/search.html" target="_blank">Search</a> <br> <a href="http://java.sun.com/j2ee/1.4/docs/tutorial/information/sendusmail.html" target="_blank">Feedback</a></font> </font> </td> </tr> </table> <img src="images/blueline.gif" width="550" height="8" ALIGN="BOTTOM" NATURALSIZEFLAG="3" ALT="Divider"> <blockquote><a name="wp84680"> </a><h2 class="pHeading1">Functions</h2><a name="wp84716"> </a><p class="pBody"><a href="JSTL8.html#wp84687">Table 14-9</a> lists the JSTL functions</p><div align="left"><table border="1" summary="Functions" id="wp84687"> <caption><a name="wp84687"> </a><div class="pTableTitle">Table 14-9 Functions </div></caption> <tr align="center"> <th><a name="wp86956"> </a><div class="pCellHeading">Area</div></th> <th><a name="wp86958"> </a><div class="pCellHeading">Function</div></th> <th><a name="wp86960"> </a><div class="pCellHeading">Tags</div></th> <th><a name="wp86962"> </a><div class="pCellHeading">Prefix</div></th></tr> <tr align="left"> <td colspan="1" rowspan="2"><a name="wp84695"> </a><div class="pCellHeading">Functions</div></td> <td><a name="wp84697"> </a><div class="pCellBody">Collection length</div></td> <td><a name="wp84699"> </a><div class="pCellBody">length</div></td> <td colspan="1" rowspan="2"><a name="wp84701"> </a><div class="pCellHeading">fn</div></td></tr> <tr align="left"> <td><a name="wp84705"> </a><div class="pCellBody">String <br />manipulation</div></td> <td><a name="wp84707"> </a><div class="pCellBody"><code class="cCode">toUpperCase, toLowerCase</code></div><a name="wp84708"> </a><div class="pCellBody"><code class="cCode">substring, substringAfter, <br />substringBefore</code></div><a name="wp84709"> </a><div class="pCellBody"><code class="cCode">trim</code></div><a name="wp84710"> </a><div class="pCellBody"><code class="cCode">replace</code></div><a name="wp84711"> </a><div class="pCellBody"><code class="cCode">indexOf, startsWith, endsWith, contains, containsIgnoreCase</code></div><a name="wp84712"> </a><div class="pCellBody"><code class="cCode">split, join</code></div><a name="wp84713"> </a><div class="pCellBody"><code class="cCode">escapeXml</code></div></td></tr></table></div><p class="pBody"></p><a name="wp84829"> </a><p class="pBody">While the <code class="cCode">java.util.Collection</code> interface defines a <code class="cCode">size</code> method, it does not conform to the JavaBeans design pattern for properties and cannot be accessed via the JSP expression language. The <code class="cCode">length</code> function can be applied to any collection supported by the c<code class="cCode">:forEach</code> and returns the length of the collection. When applied to a <code class="cCode">String</code>, it returns the number of characters in the string.</p><a name="wp86013"> </a><p class="pBody">For example, the <code class="cCode">index.jsp</code> page of the <code class="cCode">hello1</code> application introduced in Chapter <a href="WebApp.html#wp83291">3</a> uses the <code class="cCode">fn:length</code> function and <code class="cCode">c:if </code>tag to determine whether to include a response page:</p><div class="pPreformattedRelative"><pre class="pPreformattedRelative"><%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %><%@ taglib uri="http://java.sun.com/jsp/jstl/functions" prefix="fn" %><html><head><title>Hello</title></head>...<input type="text" name="username" size="25"><p></p><input type="submit" value="Submit"><input type="reset" value="Reset"></form><c:if test="${fn:length(param.username) > 0}" > <%@include file="response.jsp" %></c:if></body></html><a name="wp86014"> </a></pre></div><a name="wp85881"> </a><p class="pBody">The rest of the JSTL functions are concerned with string manipulation:</p><div class="pSmartList1"><ul class="pSmartList1"><a name="wp84719"> </a><div class="pSmartList1"><li><code class="cCode">toUpperCase</code>, <code class="cCode">toLowerCase</code> - Changes the capitalization of a string.</li></div><a name="wp84720"> </a><div class="pSmartList1"><li><code class="cCode">substring</code>, <code class="cCode">substringBefore</code>, <code class="cCode">substringAfter</code> - Gets a subset of a string.</li></div><a name="wp84721"> </a><div class="pSmartList1"><li><code class="cCode">trim</code> - Trims whitespace from a string.</li></div><a name="wp84722"> </a><div class="pSmartList1"><li><code class="cCode">replace</code> - Replaces characters in a string.</li></div><a name="wp84723"> </a><div class="pSmartList1"><li><code class="cCode">indexOf</code>, <code class="cCode">startsWith</code>, <code class="cCode">endsWith</code>, <code class="cCode">contains</code>, <code class="cCode">containsIgnoreCase</code> - Checks if a string contains another string.</li></div><a name="wp84724"> </a><div class="pSmartList1"><li><code class="cCode">split</code> - Splits a string into an array.</li></div><a name="wp84725"> </a><div class="pSmartList1"><li><code class="cCode">join</code> - Joins a collection into a string.</li></div><a name="wp84726"> </a><div class="pSmartList1"><li><code class="cCode">escapeXml</code> - Escapes XML characters in a string.</li></div></ul></div> </blockquote> <img src="images/blueline.gif" width="550" height="8" ALIGN="BOTTOM" NATURALSIZEFLAG="3" ALT="Divider"> <table width="550" summary="layout" id="SummaryNotReq1"> <tr> <td align="left" valign="center"> <font size="-1"> <a href="http://java.sun.com/j2ee/1.4/download.html#tutorial" target="_blank">Download</a> <br> <a href="http://java.sun.com/j2ee/1.4/docs/tutorial/information/faq.html" target="_blank">FAQ</a> <br> <a href="http://java.sun.com/j2ee/1.4/docs/tutorial/information/history.html" target="_blank">History</a> </td> <td align="center" valign="center"><a accesskey="p" href="JSTL7.html"><img id="LongDescNotReq1" src="images/PrevArrow.gif" width="26" height="26" border="0" alt="Prev" /></a><a accesskey="c" href="J2EETutorialFront.html"><img id="LongDescNotReq1" src="images/UpArrow.gif" width="26" height="26" border="0" alt="Home" /></a><a accesskey="n" href="JSTL9.html"><img id="LongDescNotReq3" src="images/NextArrow.gif" width="26" height="26" border="0" alt="Next" /></a><a accesskey="i" href="J2EETutorialIX.html"></a> </td> <td align="right" valign="center"> <font size="-1"> <a href="http://java.sun.com/j2ee/1.4/docs/api/index.html" target="_blank">API</a> <br> <a href="http://java.sun.com/j2ee/1.4/docs/tutorial/information/search.html" target="_blank">Search</a> <br> <a href="http://java.sun.com/j2ee/1.4/docs/tutorial/information/sendusmail.html" target="_blank">Feedback</a></font> </font> </td> </tr> </table> <img src="images/blueline.gif" width="550" height="8" ALIGN="BOTTOM" NATURALSIZEFLAG="3" ALT="Divider"><p><font size="-1">All of the material in <em>The J2EE(TM) 1.4 Tutorial</em> is <a href="J2EETutorialFront2.html">copyright</a>-protected and may not be published in other workswithout express written permission from Sun Microsystems.</font> </body></html>⌨️ 快捷键说明
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