WEB系统截取字符串的几种方法

来源：互联网发布：june软件编辑：程序博客网时间：2024/05/21 14:00

在做WEB系统的时候，经常要涉及到截取字符串的问题，比如首页新闻的长度。现在提供几种JAVA方面的字符串截取方法，这些方法来源于网络，我只是做一些总结的工作。

1.最好用的方式是用JSTL提供的标签fn，用fn配合c标签可以很好的控制字符串长度：例子如下<%@ page language="java" pageEncoding="UTF-8"%><%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c"%><%@ taglib uri="http://java.sun.com/jsp/jstl/functions" prefix="fn"%><c:set var="test" value="1234567890123456789" /><!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html> <head> <title>My JSP 'testString.jsp' starting page</title> </head> <body> <c:if test="${fn:length(test)>10}"> <c:out value="${fn:substring(test,0,7)}" /> </c:if> <c:if test="${fn:length(test)<=10}">${test}</c:if> </body></html>本文来自CSDN博客，转载请标明出处：http://blog.csdn.net/gaochc/archive/2008/03/06/2153020.aspx

2.采用自定义EL函数或者自定义标签：这种情况下往往是因为默认的fn标签不能够满足程序需求，可以用自定义EL函数：例子如下：

开发步骤：

1、添加实现静态方法
/** * @author X.Ing's Blog */ public class StringUtils { /** * @param str: * source string * @param width: * string's byte width * @param ellipsis: * a string added to abbreviate string bottom * @return String Object * @author X.Ing's Blog * @see <a href="http://blog.csdn.net/xxd851116/" mce_href="http://blog.csdn.net/xxd851116/">X.Ing's Blog</a> */ public static String abbreviate(String str, int width, String ellipsis) { if (str == null || "".equals(str)) { return ""; } int d = 0; // byte length int n = 0; // char length for (; n < str.length(); n++) { d = (int) str.charAt(n) > 256 ? d + 2 : d + 1; if (d > width) { break; } } if (d > width) { n = n - ellipsis.length() / 2; return str.substring(0, n > 0 ? n : 0) + ellipsis; } return str = str.substring(0, n); } } /** * @author X.Ing's Blog */public class StringUtils { /** * @param str: * source string * @param width: * string's byte width * @param ellipsis: * a string added to abbreviate string bottom * @return String Object * @author X.Ing's Blog * @see <a href="http://blog.csdn.net/xxd851116/" mce_href="http://blog.csdn.net/xxd851116/">X.Ing's Blog</a> */ public static String abbreviate(String str, int width, String ellipsis) { if (str == null || "".equals(str)) { return ""; } int d = 0; // byte length int n = 0; // char length for (; n < str.length(); n++) { d = (int) str.charAt(n) > 256 ? d + 2 : d + 1; if (d > width) { break; } } if (d > width) { n = n - ellipsis.length() / 2; return str.substring(0, n > 0 ? n : 0) + ellipsis; } return str = str.substring(0, n); }}
2、添加标签库描述符tld文件（Tag Library Descriptor），在其中注册该静态方法

<?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 web-jsptaglibrary_2_0.xsd" version="2.0"> <description>StringUtils</description> <tlib-version>1.0</tlib-version> <short-name>StringUtils</short-name> <uri>http://blog.csdn.net/xxd851116</uri> <function> <description>StringUtils</description> <name>abbreviate</name> <function-class>com.xxd.utils.StringUtils</function-class> <function-signature>java.lang.String abbreviate(java.lang.String, int, java.lang.String)</function-signature> </function> </taglib> <?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 web-jsptaglibrary_2_0.xsd" version="2.0"> <description>StringUtils</description> <tlib-version>1.0</tlib-version> <short-name>StringUtils</short-name> <uri>http://blog.csdn.net/xxd851116</uri> <function> <description>StringUtils</description> <name>abbreviate</name> <function-class>com.xxd.utils.StringUtils</function-class> <function-signature>java.lang.String abbreviate(java.lang.String, int, java.lang.String)</function-signature> </function> </taglib>
3、在JSP页面导入标签库（不用再Web.xml中说明tld的位置，servlet容器可自动搜索tld文件，因此可打包成jar文件）

<%@taglib uri="http://blog.csdn.net/xxd851116" prefix="fnx" %>

注意：

(1) 此处的uri和tld文件中的uri必须相一致，这个不用说明吧？哈哈。

(2) prefix是函数使用前缀。

4、页面使用，超级简单！

view plaincopy to clipboardprint?
${fnx:abbreviate('要截取的源字符串', '字节长度', '尾部追加字符')}
${fnx:abbreviate('要截取的源字符串', '字节长度', '尾部追加字符')}

5、测试结果

【代码】

<body> ${fnx:abbreviate('a我b是c，中d国e人f', 2 * 0, '')} ${fnx:abbreviate('a我b是c，中d国e人f', 2 * 1, '')} ${fnx:abbreviate('a我b是c，中d国e人f', 2 * 2, '')} ${fnx:abbreviate('a我b是c，中d国e人f', 2 * 3, '')} ${fnx:abbreviate('a我b是c，中d国e人f', 2 * 4, '')} ${fnx:abbreviate('a我b是c，中d国e人f', 2 * 5, '')} ${fnx:abbreviate('a我b是c，中d国e人f', 2 * 6, '')} ${fnx:abbreviate('a我b是c，中d国e人f', 2 * 7, '')} ${fnx:abbreviate('a我b是c，中d国e人f', 2 * 8, '')} ${fnx:abbreviate('a我b是c，中d国e人f', 2 * 9, '')} ${fnx:abbreviate('a我b是c，中d国e人f', 2 * 0, '...')} ${fnx:abbreviate('a我b是c，中d国e人f', 2 * 1, '...')} ${fnx:abbreviate('a我b是c，中d国e人f', 2 * 2, '...')} ${fnx:abbreviate('a我b是c，中d国e人f', 2 * 3, '...')} ${fnx:abbreviate('a我b是c，中d国e人f', 2 * 4, '...')} ${fnx:abbreviate('a我b是c，中d国e人f', 2 * 5, '...')} ${fnx:abbreviate('a我b是c，中d国e人f', 2 * 6, '...')} ${fnx:abbreviate('a我b是c，中d国e人f', 2 * 7, '...')} ${fnx:abbreviate('a我b是c，中d国e人f', 2 * 8, '...')} ${fnx:abbreviate('a我b是c，中d国e人f', 2 * 9, '...')} </body> <body>${fnx:abbreviate('a我b是c，中d国e人f', 2 * 0, '')} ${fnx:abbreviate('a我b是c，中d国e人f', 2 * 1, '')} ${fnx:abbreviate('a我b是c，中d国e人f', 2 * 2, '')} ${fnx:abbreviate('a我b是c，中d国e人f', 2 * 3, '')} ${fnx:abbreviate('a我b是c，中d国e人f', 2 * 4, '')} ${fnx:abbreviate('a我b是c，中d国e人f', 2 * 5, '')} ${fnx:abbreviate('a我b是c，中d国e人f', 2 * 6, '')} ${fnx:abbreviate('a我b是c，中d国e人f', 2 * 7, '')} ${fnx:abbreviate('a我b是c，中d国e人f', 2 * 8, '')} ${fnx:abbreviate('a我b是c，中d国e人f', 2 * 9, '')} ${fnx:abbreviate('a我b是c，中d国e人f', 2 * 0, '...')} ${fnx:abbreviate('a我b是c，中d国e人f', 2 * 1, '...')} ${fnx:abbreviate('a我b是c，中d国e人f', 2 * 2, '...')} ${fnx:abbreviate('a我b是c，中d国e人f', 2 * 3, '...')} ${fnx:abbreviate('a我b是c，中d国e人f', 2 * 4, '...')} ${fnx:abbreviate('a我b是c，中d国e人f', 2 * 5, '...')} ${fnx:abbreviate('a我b是c，中d国e人f', 2 * 6, '...')} ${fnx:abbreviate('a我b是c，中d国e人f', 2 * 7, '...')} ${fnx:abbreviate('a我b是c，中d国e人f', 2 * 8, '...')} ${fnx:abbreviate('a我b是c，中d国e人f', 2 * 9, '...')} </body>

【结果】

a
a我b
a我b是
a我b是c
a我b是c，
a我b是c，中d
a我b是c，中d国
a我b是c，中d国e
a我b是c，中d国e人f

...
...
a我...
a我b...
a我b是...
a我b是c...
a我b是c，中...
a我b是c，中d...
a我b是c，中d国...
a我b是c，中d国e人f

3.修改fn标签的内容，这种情况下往往是因为和第二点相同的情况或者fn对中文支持不是很好，例子如下：

/* * The contents of this file are subject to the terms * of the Common Development and Distribution License * (the "License"). You may not use this file except * in compliance with the License. * * You can obtain a copy of the license at * glassfish/bootstrap/legal/CDDLv1.0.txt or * https://glassfish.dev.java.net/public/CDDLv1.0.html. * See the License for the specific language governing * permissions and limitations under the License. * * When distributing Covered Code, include this CDDL * HEADER in each file and include the License file at * glassfish/bootstrap/legal/CDDLv1.0.txt. If applicable, * add the following below this CDDL HEADER, with the * fields enclosed by brackets "[]" replaced with your * own identifying information: Portions Copyright [yyyy] * [name of copyright owner] * * Copyright 2005 Sun Microsystems, Inc. All rights reserved. * * Portions Copyright Apache Software Foundation. */ package org.apache.taglibs.standard.functions; import java.lang.reflect.Array; import java.util.Collection; import java.util.Enumeration; import java.util.Iterator; import java.util.Map; import java.util.StringTokenizer; import javax.servlet.jsp.JspTagException; import org.apache.taglibs.standard.resources.Resources; import org.apache.taglibs.standard.tag.common.core.Util; /** * JSTL Functions * * @author Pierre Delisle */ public class Functions { //********************************************************************* // String capitalization /** * Converts all of the characters of the input string to upper case. */ public static String toUpperCase(String input) { return input.toUpperCase(); } /** * Converts all of the characters of the input string to lower case. */ public static String toLowerCase(String input) { return input.toLowerCase(); } //********************************************************************* // Substring processing public static int indexOf(String input, String substring) { if (input == null) input = ""; if (substring == null) substring = ""; return input.indexOf(substring); } public static boolean contains(String input, String substring) { return indexOf(input, substring) != -1; } public static boolean containsIgnoreCase(String input, String substring) { if (input == null) input = ""; if (substring == null) substring = ""; String inputUC = input.toUpperCase(); String substringUC = substring.toUpperCase(); return indexOf(inputUC, substringUC) != -1; } public static boolean startsWith(String input, String substring) { if (input == null) input = ""; if (substring == null) substring = ""; return input.startsWith(substring); } public static boolean endsWith(String input, String substring) { if (input == null) input = ""; if (substring == null) substring = ""; int index = input.indexOf(substring); if (index == -1) return false; if (index == 0 && substring.length() == 0) return true; return (index == input.length() - substring.length()); } public static String substring(String input, int beginIndex, int endIndex) { if (input == null) input = ""; if (beginIndex >= input.length()) return ""; if (beginIndex < 0) beginIndex = 0; if (endIndex < 0 || endIndex > input.length()) endIndex = input.length(); if (endIndex < beginIndex) return ""; return input.substring(beginIndex, endIndex); } public static String substringAfter(String input, String substring) { if (input == null) input = ""; if (input.length() == 0) return ""; if (substring == null) substring = ""; if (substring.length() == 0) return input; int index = input.indexOf(substring); if (index == -1) { return ""; } else { return input.substring(index+substring.length()); } } public static String substringBefore(String input, String substring) { if (input == null) input = ""; if (input.length() == 0) return ""; if (substring == null) substring = ""; if (substring.length() == 0) return ""; int index = input.indexOf(substring); if (index == -1) { return ""; } else { return input.substring(0, index); } } //********************************************************************* // Character replacement public static String escapeXml(String input) { if (input == null) return ""; return Util.escapeXml(input); } public static String trim(String input) { if (input == null) return ""; return input.trim(); } public static String replace( String input, String substringBefore, String substringAfter) { if (input == null) input = ""; if (input.length() == 0) return ""; if (substringBefore == null) substringBefore = ""; if (substringBefore.length() == 0) return input; StringBuffer buf = new StringBuffer(input.length()); int startIndex = 0; int index; while ((index = input.indexOf(substringBefore, startIndex)) != -1) { buf.append(input.substring(startIndex, index)).append(substringAfter); startIndex = index + substringBefore.length(); } return buf.append(input.substring(startIndex)).toString(); } public static String[] split( String input, String delimiters) { String[] array; if (input == null) input = ""; if (input.length() == 0) { array = new String[1]; array[0] = ""; return array; } if (delimiters == null) delimiters = ""; StringTokenizer tok = new StringTokenizer(input, delimiters); int count = tok.countTokens(); array = new String[count]; int i = 0; while (tok.hasMoreTokens()) { array[i++] = tok.nextToken(); } return array; } //********************************************************************* // Collections processing public static int length(Object obj) throws JspTagException { if (obj == null) return 0; if (obj instanceof String) return ((String)obj).length(); if (obj instanceof Collection) return ((Collection)obj).size(); if (obj instanceof Map) return ((Map)obj).size(); int count = 0; if (obj instanceof Iterator) { Iterator iter = (Iterator)obj; count = 0; while (iter.hasNext()) { count++; iter.next(); } return count; } if (obj instanceof Enumeration) { Enumeration enum_ = (Enumeration)obj; count = 0; while (enum_.hasMoreElements()) { count++; enum_.nextElement(); } return count; } try { count = Array.getLength(obj); return count; } catch (IllegalArgumentException ex) {} throw new JspTagException(Resources.getMessage("FOREACH_BAD_ITEMS")); } public static String join(String[] array, String separator) { if (array == null) return ""; if (separator == null) separator = ""; StringBuffer buf = new StringBuffer(); for (int i=0; i<array.length; i++) { buf.append(array[i]); if (i < array.length-1) buf.append(separator); } return buf.toString(); } public static String cutString(String input,int length){ if (input.length()<=length) { return input; }else{ return input.substring(0,length)+"..."; } } }

最后一段是自己加的方法。

和在fn.tld 中增加了

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

在把编译后的Functions.class 文件去替换 jstl1.2.jar解压后的相应位置的Functions.class 和 fn.tld 文件再做成Jar包就可以用了（做成Jar包的方法，按解压出来的目录不变，替换以后，打个zip 包，修改后缀为jar 就可以了这种方法比较方便）

在页面中使用就是

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

${fn:cutString(product.enDesc ,15) }

这里也提供做好了的jstl1.2.jar文件，不用自己再去改了

4.用JS实现截取字符串，这种情况是不推荐的，不过介绍一下：

<mce:script language="javascript"></mce:script>

5.用CSS截取字符串，这种方式应该说应用范围不广，因为好像只支持IE（不知道对不对）

<div style="width:100px; overflow:hidden; white-space:nowrap; text-overflow:ellipsis">采用CSS格式截图字符串固定长度<div>