JSP_EXTENDS

BlockTag:import java.io.IOException;import javax.servlet.jsp.JspException;import javax.servlet.jsp.tagext.TagSupport;public class BlockTag extends TagSupport{    private static final long serialVersionUID = -8246166191638588615L;    private String name;    public void setName(String name) {        this.name = name;    }    /**     * @return EVAL_BODY_INCLUDE or EVAL_BODY_BUFFERED or SKIP_BODY     */    @Override    public int doStartTag() throws JspException {        return getOverriedContent() == null ? EVAL_BODY_INCLUDE : SKIP_BODY;    }    /**     * @return EVAL_PAGE or SKIP_PAGE     */    @Override    public int doEndTag() throws JspException {        String overriedContent = getOverriedContent();        if(overriedContent == null) {            return EVAL_PAGE;        }        try {            pageContext.getOut().write(overriedContent);        } catch (IOException e) {            throw new JspException("write overridedContent occer IOException,block name:"+name,e);        }        return EVAL_PAGE;    }    private String getOverriedContent() {        String varName = Utils.getOverrideVariableName(name);        return (String)pageContext.getRequest().getAttribute(varName);    }}

OverrideTag:import javax.servlet.jsp.JspException;import javax.servlet.jsp.tagext.BodyContent;import javax.servlet.jsp.tagext.BodyTagSupport;public class OverrideTag extends BodyTagSupport {    private static final long serialVersionUID = -8379959647039117369L;    private String name;    public void setName(String name) {        this.name = name;    }    @Override    public int doStartTag() throws JspException {        return isOverrided() ? SKIP_BODY : EVAL_BODY_BUFFERED;    }    @Override    public int doEndTag() throws JspException {        if (isOverrided()) {            return EVAL_PAGE;        }        BodyContent b = getBodyContent();        // System.out.println("Override.content:"+b.getString());        String varName = Utils.getOverrideVariableName(name);        pageContext.getRequest().setAttribute(varName, b.getString());        return EVAL_PAGE;    }    private boolean isOverrided() {        String varName = Utils.getOverrideVariableName(name);        return pageContext.getRequest().getAttribute(varName) != null;    }}

Utils:class Utils {    public static String BLOCK = "__jsp_override__";    static String getOverrideVariableName(String name) {        return BLOCK + name;    }}

jsp_layout.tld:<?xml version="1.0" encoding="UTF-8" ?><taglib xmlns="http://java.sun.com/xml/ns/j2ee" xmlns:xsi="http://www.w3g.org/2001/XMLSchema-instance"    xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee web-jsptaglibrary_2_0.xsd"    version="2.0">    <tlib-version>1.2</tlib-version>    <jsp-version>1.2</jsp-version>    <short-name>Taglib</short-name>    <uri>jsp_layout.tld</uri>    <description>jsp模板继承</description>    <tag>        <name>block</name><!--tag的名字 -->        <tag-class>org.study.web.tags.BlockTag</tag-class><!--其中对应的java类 -->        <body-content>jsp</body-content>        <!-- JSP,empty,scriptless,tagdependent JSP:接受所有JSP语法，如定制的或内部的tag、scripts、静态HTML、脚本元素、             JSP指令和动作 empty:空标记，即起始标记和结束标记之间没有内容 scriptless:接受文本、EL和JSP动作。如<%=request.getProtocol()%>使用             <body-content> scriptless </body-content>则报错 tagdependent:标签体内容直接被写入BodyContent，由自定义标签类来进行处理，而不被JSP容器解释 -->        <attribute><!--tag的参数 -->            <name>name</name><!--参数名 -->            <required>true</required><!-- 是否是必填选项 -->            <rtexprvalue>true</rtexprvalue><!--是否可以动态赋值 -->            <type>java.lang.String</type><!--参数类型 -->        </attribute>        <!-- 支持动态属性(必须实现DynamicAttributes接口) <dynamic-attributes>true</dynamic-attributes> -->    </tag>    <tag>        <name>override</name>        <tag-class>org.study.web.tags.OverrideTag</tag-class>        <body-content>jsp</body-content>        <attribute>            <name>name</name>            <required>true</required>            <rtexprvalue>true</rtexprvalue>            <type>java.lang.String</type>        </attribute>    </tag></taglib>

layout.jsp:<%@ page language="java" import="java.util.*" pageEncoding="utf-8"%><%    String path = request.getContextPath();    String basePath = request.getScheme() + "://" + request.getServerName() + ":" + request.getServerPort()            + path + "/";%><%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c"%><%@ taglib uri="jsp_layout.tld" prefix="rapid"%><!DOCTYPE html><html lang="zh-CN"><head><base href="<%=basePath%>"><rapid:block name="head">    <meta charset="utf-8">    <meta http-equiv="X-UA-Compatible" content="IE=edge">    <meta name="viewport" content="width=device-width, initial-scale=1">    <!-- 上述3个meta标签*必须*放在最前面，任何其他内容都*必须*跟随其后！ -->    <meta name="description" content="">    <meta name="author" content="">    <link rel="icon" href="../../favicon.ico">    <title>Starter Template for Bootstrap</title>    <!-- Bootstrap core CSS -->    <link href="frameworks/bootstrap3/css/bootstrap.min.css"        rel="stylesheet">    <!-- Custom styles for this template -->    <link href="custom/css/plugin/starter-template.css" rel="stylesheet">    <!-- Just for debugging purposes. Don't actually copy these 2 lines! -->    <!--[if lt IE 9]><script src="frameworks/bootstrap/js/ie8-responsive-file-warning.js"></script><![endif]-->    <script src="frameworks/bootstrap3/js/ie-emulation-modes-warning.js"></script>    <!-- HTML5 shim and Respond.js for IE8 support of HTML5 elements and media queries -->    <!--[if lt IE 9]>      <script src="frameworks/bootstrap3/js/html5shiv.min.js"></script>      <script src="frameworks/bootstrap3/js/respond.min.js"></script>    <![endif]--></rapid:block></head><body>    <nav class="navbar navbar-inverse navbar-fixed-top">        <div class="container">            <div class="navbar-header">                <button type="button" class="navbar-toggle collapsed"                    data-toggle="collapse" data-target="#navbar" aria-expanded="false"                    aria-controls="navbar">                    <span class="sr-only">Toggle navigation</span> <span                        class="icon-bar"></span> <span class="icon-bar"></span> <span                        class="icon-bar"></span>                </button>                <a class="navbar-brand" href="#">Bootstrap theme</a>            </div>            <div id="navbar" class="navbar-collapse collapse">                <ul class="nav navbar-nav">                    <li class="active"><a href="#">Home</a></li>                    <li><a href="#about">About</a></li>                    <li><a href="#contact">Contact</a></li>                    <li class="dropdown"><a href="#" class="dropdown-toggle"                        data-toggle="dropdown" role="button" aria-haspopup="true"                        aria-expanded="false">Dropdown <span class="caret"></span></a>                        <ul class="dropdown-menu">                            <li><a href="#">Action</a></li>                            <li><a href="#">Another action</a></li>                            <li><a href="#">Something else here</a></li>                            <li role="separator" class="divider"></li>                            <li class="dropdown-header">Nav header</li>                            <li><a href="#">Separated link</a></li>                            <li><a href="#">One more separated link</a></li>                        </ul></li>                </ul>            </div>            <!--/.nav-collapse -->        </div>    </nav>    <div class="container">        <rapid:block name="body">            <div class="starter-template">                <h1>Bootstrap starter template</h1>                <p class="lead">                    Use this document as a way to quickly start any new project.<br>                    All you get is this text and a mostly barebones HTML document.                </p>            </div>        </rapid:block>    </div>    <!-- /.container -->    <rapid:block name="script">        <!-- Bootstrap core JavaScript    ================================================== -->        <!-- Placed at the end of the document so the pages load faster -->        <script src="frameworks/bootstrap3/js/jquery.min.js"></script>        <script src="frameworks/bootstrap3/js/bootstrap.min.js"></script>        <!-- IE10 viewport hack for Surface/desktop Windows 8 bug -->        <script src="frameworks/bootstrap3/js/ie10-viewport-bug-workaround.js"></script>    </rapid:block></body></html>

home.jsp:<%@ taglib uri="jsp_layout.tld" prefix="rapid"%><rapid:override name="body">    Youth is not a time of life, it is a state of mind.青春不是生命的一瞬，而是一种自然的心境。</rapid:override><%@ include file="../layout/layout.jsp"%>