jsp中通过自定义fn标签实现指定长度字符，多余的用……表示

    今天做到在jsp 页面中显示数据的时候，由于数据比较多，一下子表格就拉开了 ，变形了。想到以前在ASP.NET中做过，但那完全不一样，那里直接可能调用后台代码，而在jsp页面中呢？我也试了一下，但是又不能次页面中的数据传进去也是不行。<%= Util.cutString("${user.name}",10)%>,没想到这样也没用，只是一个字符串死的。

    解决方法 ，我想到了  jstl 标签中的 fn 标签，但找了一下，都用不上，没有自己想用的方法。我想自己可不可以加个方法进去呢？就找  jstl  的源码。和打成的JAR  文件，看了一下  有关fn 标签的实现，没想到只有一个Functions 类型里面有一些静态的方法修改一下配置文件就Ok了。这是加了以后Functions 类的代码：

/*
 * 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;

/**
 * <p>JSTL Functions</p>
 * 
 * @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

评论

2 楼 jmu 2009-08-16  

contains  判断字符串是否包含另外一个字符串  <c:if test="${fn:contains(name, searchString)}">
containsIgnoreCase 判断字符串是否包含另外一个字符串(大小写无关) <c:if test="${fn:containsIgnoreCase(name, searchString)}">
endsWith 判断字符串是否以另外字符串结束 <c:if test="${fn:endsWith(filename, ".txt")}">
escapeXml 把一些字符转成XML表示，例如<字符应该转为&lt; ${fn:escapeXml(param:info)}
indexOf 子字符串在母字符串中出现的位置 ${fn:indexOf(name, "-")}
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, ";")}
length 获取字符串的长度，或者数组的大小 ${fn:length(shoppingCart.products)}
replace 替换字符串中指定的字符 ${fn:replace(text, "-", "&#149;")}
split 把字符串按照指定字符切分 ${fn:split(customerNames, ";")}
startsWith 判断字符串是否以某个子串开始 <c:if test="${fn:startsWith(product.id, "100-")}">
substring 获取子串 ${fn:substring(zip, 6, -1)}
substringAfter

获取从某个字符所在位置开始的子串
${fn:substringAfter(zip, "-")}
substringBefore 获取从开始到某个字符所在位置的子串 ${fn:substringBefore(zip, "-")}
toLowerCase 转为小写 ${fn.toLowerCase(product.name)}
toUpperCase 转为大写字符 ${fn.UpperCase(product.name)}
trim 去除字符串前后的空格 ${fn.trim(name)}

1 楼 myyate 2009-08-16  

我晕，这个完全可以用css来控制的，何必这么麻烦？

text-overflow:ellipsis;
overflow:hidden;
width:100px;