第九章自定义标签第四节自定义有标签体的标签
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2022-06-09 09:18:02
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IterateTag.jsp
<%@page import="java.util.*"%>
<%@ page language="java" contentType="text/html; charset=utf-8"
pageEncoding="utf-8"%>
<%@ taglib prefix="please" uri="/WEB-INF/lang.tld"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<title>Insert title here</title>
<%
List people = new ArrayList();
people.add("王小二");
people.add("思思光");
people.add("*");
pageContext.setAttribute("people", people);
%>
</head>
<body>
<please:iterate items="people" var="p">
<h2>${p }</h2>
</please:iterate>
</body>
</html>iterateTag.java
package com.lang.tag;
import java.util.List;
import java.io.IOException;
import java.util.Iterator;
import javax.servlet.jsp.JspException;
import javax.servlet.jsp.JspWriter;
import javax.servlet.jsp.tagext.TagSupport;
public class IterateTag extends TagSupport{
/**
*
*/
private static final long serialVersionUID = 1L;
private String var;
private String items;
private Iterator iter;
public String getVar() {
return var;
}
public void setVar(String var) {
this.var = var;
}
public String getItems() {
return items;
}
public void setItems(String items) {
this.items = items;
}
public Iterator getIter() {
return iter;
}
public void setIter(Iterator iter) {
this.iter = iter;
}
@Override
public int doStartTag() throws JspException {
Object value = this.pageContext.getAttribute(items);
if (value!=null && value instanceof List) {
this.iter = ((List)value).iterator();
if(iter.hasNext()) {
this.pageContext.setAttribute(var, iter.next());
return TagSupport.EVAL_BODY_INCLUDE; //执行标签体
}else {
return TagSupport.SKIP_BODY; //退出标签执行
}
}else {
return TagSupport.SKIP_BODY;
}
}
@Override
public int doAfterBody() throws JspException {
if(iter.hasNext()) {
this.pageContext.setAttribute(var, iter.next());
return TagSupport.EVAL_BODY_AGAIN; //在执行一次标签体
}else {
return TagSupport.SKIP_BODY; //退出标签
}
}
}
lang.tld
<?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">
<tlib-version>1.0</tlib-version>
<short-name>pleaseTag</short-name>
<tag>
<name>iterate</name>
<tag-class>
com.lang.tag.IterateTag
</tag-class>
<body-content>JSP</body-content>
<attribute>
<name>var</name>
<required>true</required>
<rtexprvalue>true</rtexprvalue>
</attribute>
<attribute>
<name>items</name>
<required>true</required>
<rtexprvalue>true</rtexprvalue>
</attribute>
</tag>
</taglib>运行结果：