自定义 jstl 标签

 java 类 StringReplaceTag.java

import java.io.IOException;import javax.servlet.jsp.JspException;import javax.servlet.jsp.JspTagException;import javax.servlet.jsp.PageContext;import javax.servlet.jsp.tagext.BodyTagSupport;import org.apache.taglibs.standard.tag.common.core.Util;/** * 自定义jstl 标签 字符串替换 * @author okttl * */public class StringReplaceTag extends BodyTagSupport{private static final long serialVersionUID = 1L;private static final  String REPLACEMENT_DEFAULT = "*";private Object value;private String var;private Integer start;private Integer end;private String replacement;private int scope;  private int median; //位数/** * 设置值 * @param value * @throws JspTagException */public void setValue(Object value) throws JspTagException {     this.value = value;}/** * 设置变量名 * @param var */public void setVar(String var) {     this.var = var;}/** * 设置开始索引 * @param start */public void setStart(Integer start) {this.start = start;}/** * 设置结束索引 * @param end */public void setEnd(Integer end) {this.end = end;}/** * 设置替换字符 默认 为* * @param replacement */public void setReplacement(String replacement) {this.replacement = replacement;}/** * 设置作用域 可取值 * request * session * application * @param scope */public void setScope(String scope) {this.scope = Util.getScope(scope);}/** * 设置显示替换符位数 当替换符为单个字符时有效 * @param median */public void setMedian(int median) {this.median = median;}/** * 默认构造方法 */public StringReplaceTag() {super();init();}/** * 初始化方法 */private void init(){start = end = 0;median = -1;replacement = REPLACEMENT_DEFAULT;scope = PageContext.PAGE_SCOPE;} @Overridepublic int doEndTag() throws JspException {String formatted = ""; if (value == null){ formatted = ""; } formatted = value.toString();   int l = formatted.length();      if(start == null){      start = 0;       }else if(start < 0){      start = l;      }else if(start >= l){      start = l;      }      if(end == null){      end = l;      }else if(end < 0){      end = 0;      }else if(end > l){      end = l;      }      StringBuffer strBuf = new StringBuffer(formatted);      if(replacement.length()==1){      if(median==-1 && end > start){      median = end - start;      }      if(median>0){      String temp = replacement;      replacement = "";      for(int i=0;i<median;i++){      replacement=replacement+temp;       }      }      };      formatted = strBuf.replace(start, end, replacement).toString();<span style="white-space:pre"></span>if (var != null) {    pageContext.setAttribute(var, formatted, scope);}     <span style="white-space:pre"></span>try {    <span style="white-space:pre"></span>pageContext.getOut().print(formatted);    <span style="white-space:pre"></span>} catch (IOException ioe) {    <span style="white-space:pre"></span>throw new JspTagException(ioe.toString(), ioe);    <span style="white-space:pre"></span>}               init();return EVAL_PAGE;}

tld 文件 str.tld 放到WEB-INF下

<?xml version="1.0" encoding="UTF-8"?><taglib xmlns="http://java.sun.com/xml/ns/javaee"    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"    xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-jsptaglibrary_2_1.xsd"    version="2.1"><description>okttl Tag Library</description><tlib-version>1.0</tlib-version><short-name>str</short-name><tag><!-- 标签名称 -->        <name>replace</name>                <description>      Replacement string starting index position to the end position of the character index    </description>    <!-- java类的全名 -->        <tag-class>cn.anscm.taglibs.StringReplaceTag</tag-class>            <body-content>empty</body-content> <attribute>        <description>        value 要被替换的对象，        </description>        <name>value</name>        <required>false</required>        <rtexprvalue>true</rtexprvalue>        <deferred-value>    <type>java.lang.Object</type>        </deferred-value> </attribute>         <attribute>        <description>start - The beginning index, inclusive.\r\n起始索引（包含）。        </description>        <name>start</name>        <type>int</type>        <required>false</required>        <rtexprvalue>false</rtexprvalue>     </attribute>     <attribute>        <description>end - The ending index, exclusive.\r\n结束索引（不包含）。        </description>        <name>end</name>        <type>int</type>        <required>false</required>        <rtexprvalue>false</rtexprvalue>     </attribute>     <attribute>        <description>It is replaced with the number of bits.  The default value is the number of bits of character.When the replacement is effective as a single character \r\n被替换成的字符位数，当"replacement" 的属性值是单个字符时，有效默认值是原字符索引间的位数。        </description>        <name>median</name>        <type>int</type>        <required>false</required>        <rtexprvalue>false</rtexprvalue>     </attribute>     <attribute>        <description>replacement symbol or character or string.default "replacement" is a single character \r\n被替换为的字符,符号,或字符串        </description>        <name>replacement</name>        <required>false</required>        <rtexprvalue>false</rtexprvalue>     </attribute>         <attribute>        <description>Name of the exported scoped variablewhich stores the formatted result as aString.\r\n变量名        </description>        <name>var</name>        <required>false</required>        <rtexprvalue>false</rtexprvalue>    </attribute>    <attribute>        <description>Scope of var. \r\n变量作用域 可选值 request,sessioin,application        </description>        <name>scope</name>        <required>false</required>        <rtexprvalue>false</rtexprvalue>    </attribute>    </tag></taglib>

jsp 文件 safe.jsp

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%><%@ taglib prefix="str" uri="/WEB-INF/str.tld" %><!DOCTYPE html><html ><head><str:replace value="身份证号" start="1" end="3"   /></head><body></html >

其它属性自己测试