JSP 自定义标签学习

自定义标签执行顺序实验：

doStartTag()中的

return EVAL_BODY_INCLUDE

顺序：

setPageContext()
SetParent()
doStartTag()
doAfterBody()
doEndTag()

return SKIP_BODY

setPageContext()
setParent()
doStartTag()
doEndTag()

return EVAL_PAGE

执行顺序：

setPageContext()
setParent()
doStartTag()
setBodyContent()
doinitBody()
doAfterBody()
doEndTag()

release()

package com.chen.tag;

import javax.servlet.jsp.JspException;
import javax.servlet.jsp.PageContext;
import javax.servlet.jsp.tagext.BodyContent;
import javax.servlet.jsp.tagext.BodyTag;
import javax.servlet.jsp.tagext.Tag;

public class HelloTag implements BodyTag {
    private PageContext pageContext;
    private Tag parent;
	public int doAfterBody() throws JspException {
		System.out.println("doAfterBody()");
		return 0;
	}

	public int doEndTag() throws JspException {
		System.out.println("doEndTag()");
		try {
			pageContext.getOut().println("hello world!");
		} catch (Exception e) {
			// TODO: handle exception
		}
		return 0;
	}

	public int doStartTag() throws JspException {
		System.out.println("doStartTag()");
		//EVAL_BODY_INCLUDE 表示显示标签之间的内容
		//<mytag:hello>God</mytag:hello>
		//Godhello world!
		//SKIP_BODY的话，则不显示了
		//return EVAL_PAGE
		
		return SKIP_BODY;
	}

	public Tag getParent() {
		System.out.println("getParent()");
		return null;
	}

	public void release() {
		System.out.println("release()");
	}

	public void setPageContext(PageContext pageContext) {
		System.out.println("setPageContext()");
		this.pageContext=pageContext;
	}

	public void setParent(Tag tag) {
		System.out.println("SetParent()");
		this.parent=tag;
	}

	public void doInitBody() throws JspException {
		System.out.println("doinitBody()");
	}

	public void setBodyContent(BodyContent arg0) {
		System.out.println("setBodyContent()");
	}

}

index.jsp

<%@ page language="java" contentType="text/html; charset=utf-8"
    pageEncoding="utf-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<%@ taglib uri="/WEB-INF/hellotag.tld" prefix="mytag" %>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<title>Insert title here</title>
</head>
<body>
  
  <mytag:hello>dongdong</mytag:hello>
</body>
</html>

WEB-INF/hellotag.tld

<?xml version="1.0" encoding="utf-8"?>
<!--DOCTYPE taglib PUBLIC "-//Sun Microsystems, Inc.//DTD JSP Tag Library 1.2//EN" "http://java.sun.com/dtd/web-jsptaglibrary_1_2.dtd"-->
<taglib>
	<tlib-version>1.0</tlib-version>
	<jsp-version>1.2</jsp-version>
	<short-name>tagSample</short-name>
	<uri>/hellotag</uri>

<tag>
	<name>hello</name>
	<tag-class>com.chen.tag.HelloTag</tag-class>
	<body-content>JSP</body-content>
</tag>
</taglib>

后续：

比如使用：

<mytag:hello id="hello" name="mygod">dongdong</mytag:hello>

那么执行顺序会是：

setPageContext()
SetParent()
setID()
setName()

...[如果还有其他属性设置的话]

doStartTag()

JSP 自定义标签 学习

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