笔记之_Java的自定义标签 

自定义类：
import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.jsp.JspException;
import javax.servlet.jsp.tagext.TagSupport;
public class CalcTag extends TagSupport {
    private int numA;
    private int numB;
    public int getNumA() {
        return numA;
    }
    public void setNumA(int numA) {
        this.numA = numA;
    }
    public int getNumB() {
        return numB;
    }
    public void setNumB(int numB) {
        this.numB = numB;
    }
    @Override
    public int doStartTag() throws JspException {
        ServletResponse sr=  super.pageContext.getResponse();
         try {
            PrintWriter out=sr.getWriter();
            out.println("<h1>");
            out.print(numA);
            out.print("+");
            out.print(numB);
            out.print("=");
            out.println(numA+numB);
            out.println("</h1>");
            out.flush();
            out.close();
            
        } catch (IOException e) { 
            e.printStackTrace();
        }
        return SKIP_BODY;
    }
}

创建后缀为tld的文件：
<?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 web-jsptaglibrary_2_0.xsd">

    <tlib-version>1.0</tlib-version>
    <jsp-version>2.0</jsp-version>
    <short-name>Example TLD with Body</short-name>
    <tag>
        <name>calc</name>
        <tag-class>com.wisezone.tag.CalcTag</tag-class>
        <body-content>empty</body-content>
        <attribute>
            <name>numA</name>
            <required>true</required>
            <rtexprvalue>true</rtexprvalue>
        </attribute>
        <attribute>
            <name>numB</name>//变量名首字母不能大写
            <required>true</required>
            <rtexprvalue>true</rtexprvalue>
        </attribute> 
    </tag>
</taglib>
web.xml中配置注册：
<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://xmlns.jcp.org/xml/ns/javaee" xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd" id="WebApp_ID" version="3.1">
  <display-name>tagweb</display-name>
  <welcome-file-list>
    <welcome-file>index.html</welcome-file>
  </welcome-file-list>
  <!-- 注册 -->
  <jsp-config>
    <taglib>
        <taglib-uri>/wisezone</taglib-uri>
        <taglib-location>/WEB-INF/mytag.tld</taglib-location>
    </taglib>
  </jsp-config>
</web-app>

jsp页面使用：
<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<%@taglib uri="/wisezone" prefix="c" %>    
<!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>
</head>
<body>
    <c:calc numB="${5+3 }"numA="${8+2 }"/> 
</body>
</html>

 

posted @ 2017-11-19 16:25  莫轩ASL  阅读(154)  评论(0)    收藏  举报