菜鸟学Android笔记(四十七)：自定义标签开发案例及打包

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案例1：开发if标签

先建立一个IFTag.java

package com.Test;import java.io.IOException;import javax.servlet.jsp.JspException;import javax.servlet.jsp.tagext.SimpleTagSupport;public class IFTag extends SimpleTagSupport {    private boolean test;public void doTag() throws JspException, IOException {if(test){//this.getJspBody是为了获取标签体的JspFragment对象传递给标签处理器对象//invoke（）里面的参数是一个输出流，如果写成为空，那么将标签体的内容默认输出到浏览器显示this.getJspBody().invoke(null);}}public void setTest(boolean test) {this.test = test;}}

然后建立一个IFTag.tld文件配置上面的java文件

<?xml version="1.0" encoding="UTF-8"?><taglib version="2.0" 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"> <tlib-version>1.0</tlib-version> <short-name>IFTag</short-name> <uri>http://www.cuixueyong.com/IFTag</uri> <tag>  <description>if标签</description>  <name>if</name>  <tag-class>com.Test.IFTag</tag-class>  <body-content>scriptless</body-content>  <attribute>   <name>test</name>   <rtexprvalue>true</rtexprvalue>     </attribute> </tag></taglib>

写一个IFTag.jsp来测试

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%><%@taglib uri="http://www.cuixueyong.com/IFTag" prefix="kk" %> <%String path = request.getContextPath();String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";%><!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html>  <head>     </head>    <body> <kk:if test="true">打印出来</kk:if> <kk:if test="false">打印不出来</kk:if>  </body></html>

经过测试，在浏览器可以输出“打印出来”，而不能输出”打印不出来“

案例2：html文件转义

新建HTMLTag.java

package com.Test;import java.io.IOException;import java.io.StringWriter;import javax.servlet.jsp.JspException;import javax.servlet.jsp.tagext.SimpleTagSupport;public class HTMLTag extends SimpleTagSupport {private String filter(String message) {          if (message == null){             return (null);         }         char content[] = new char[message.length()];         message.getChars(0, message.length(), content, 0);         StringBuilder result = new StringBuilder(content.length + 50);         for (int i = 0; i < content.length; i++) {             switch (content[i]) {             case '<':                 result.append("<");                 break;             case '>':                 result.append(">");                 break;             case '&':                 result.append("&");                 break;             case '"':                 result.append(""");                 break;             default:                 result.append(content[i]);             }         }         return (result.toString());     }@Overridepublic void doTag() throws JspException, IOException {//获取一个字符串输出流，作用是保持标签体的内容StringWriter sw=new StringWriter();//将标签体的内容先输出到StringWriter流中this.getJspBody().invoke(sw);//将StringWriter流中的内容变为字符串//getBuffer()是将StringWriter流变为缓冲区，然后在转变为字符串String str=sw.getBuffer().toString();//这个时候写一个方法，将字符串里面的html代码将其转义String str1=filter(str);//返回页面的JspContext对象，然后得到它的输出流，在将字符串写入this.getJspContext().getOut().write(str1);}}

在THML.tld配置文件

<?xml version="1.0" encoding="UTF-8"?><taglib version="2.0" 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"> <tlib-version>1.0</tlib-version> <short-name>HTMLTag</short-name> <uri>http://www.cuixueyong.comHTMLTag</uri> <tag>  <name>HTMLTag</name>  <tag-class>com.Test.HTMLTag</tag-class>  <body-content>scriptless</body-content> </tag></taglib>

然后在新建HTMLTag.jsp

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%><%@taglib uri="http://www.cuixueyong.comHTMLTag"  prefix="jk"%><%String path = request.getContextPath();String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";%><!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html>  <head>    <base href="<%=basePath%>">        <title>My JSP 'HTMLTag.jsp' starting page</title>     </head>    <body>  <jk:HTMLTag><html>这是一个html的根元素</html></jk:HTMLTag>  </body></html>

在浏览器中输出可得：<html>这是一个html的根元素</html>，将字符已经转义了

案例3：防盗链

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