JSP自定义不带属性和标签体的简单标签

2018-05-28

1. 新建HelloTag类

2. 添加额外的Jar包

    (1). 右键项目 -> Build Path -> Configure Build Path ->  Libraries -> Add External JARs 
    (2). 定位到tomcat安装目录的lib文件夹下（我的是：C:\Program Files\Apache Software Foundation\Tomcat 9.0\lib）选择jsp-api.jar，确定

3. HelloTag类的详细代码

package bid.zhazhapan.fims.tag;
import java.io.IOException;
import javax.servlet.jsp.JspException;
import javax.servlet.jsp.JspWriter;
import javax.servlet.jsp.PageContext;
import javax.servlet.jsp.tagext.Tag;
public class HelloTag implements Tag {
	private PageContext pageContext;// 定义页面隐式对象
	private Tag parent;// 定义上一级标签
	// 将页面隐式对象传入到标签中
	public void setPageContext(PageContext pageContext) {
		this.pageContext = pageContext;
	}
	// 设置上一级标签
	public void setParent(Tag parent) {
		this.parent = parent;
	}
	// 标签开始时调用
	public int doStartTag() throws JspException {
		return this.SKIP_BODY;
	}
	// 标签结束时调用
	public int doEndTag() throws JspException {
		// 通过隐式对象pageContext获得隐式对象out
		JspWriter out = pageContext.getOut();
		try {
			// 向客户端输出
			out.write("Hello World<br />");
		} catch (IOException e) {
			throw new JspException("IO Error " + e.getMessage());
		}
		// 计算页面其他部分
		return this.EVAL_PAGE;
	}
	// 销毁前调用，用于释放资源
	public void release() {
	}
	public Tag getParent() {
		return null;
	}
}

4. 新建xml配置文件

    (1). 在WEB-INF下新建文件夹tlds
    (2). 新建xml文件
        Step 1
        
        Step 2
        
        Step 3
        
        Step 4
        
    (3). 配置xml文件


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11 <?xml version="1.0" encoding="UTF-8"?>
<javaee:taglib version="2.1" xmlns:javaee="http://java.sun.com/xml/ns/javaee" xmlns:xml="http://www.w3.org/XML/1998/namespace" 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 ">
  <javaee:tlib-version>1.0</javaee:tlib-version>
  <javaee:short-name>demo</javaee:short-name>
  <javaee:uri>/demo</javaee:uri>
  <javaee:tag>
  	<javaee:name>hello</javaee:name>
  	<javaee:tag-class>bid.zhazhapan.fims.tag.HelloTag</javaee:tag-class><!-- 类所在的路径 -->
  	<javaee:body-content>empty</javaee:body-content><!-- 表示无标签体内容 -->
  </javaee:tag>
</javaee:taglib>

5. 新建一个test.jsp来测试标签

    详细代码

<%@ page language="java" contentType="text/html; charset=ISO-8859-1" pageEncoding="ISO-8859-1"%>
<%@ taglib uri="WEB-INF/tlds/mytag.tld" prefix="mytag" %><!-- 这里是重点 -->
<!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=ISO-8859-1">
<title>Insert title here</title>
</head>
<body>
<mytag:hello/>
</body>
</html>

    输出内容: Hello World