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Custom tag - JSP tag Foundation

2022-06-23 08:57:00 【An Li Jiu Ge】

Catalog

Preface

One 、 know jsp Label and its characteristics

Two 、 The development of user-defined label and its application steps

         1、 know tld file ​ edit

        2、 .tld Configuration file method ：

         3、jsp adopt taglib Instruction import label Library  

         4、 Create helper class

        5、 change tld In the document tag

3、 ... and 、 Tag life cycle

Four 、 Case study

        1、z:if label

        2、z:set label    z:out label

                1、set

        2 、out

summary

Preface

Last time we shared reflections , Today's sharing is about custom tags .

One 、 know jsp Label and its characteristics

1、 form

< The start tag attribute =" Property value "> Tagging body </ End tag >

2、 classification

  1. Empty label         for example ：br,hr
  2. ui label         for example ：input,table
  3. Control tags         for example ：if.foreach （ A label that has no label body but has an output function ）
  4. Data labels         for example ：out label
     

Two 、 The development of user-defined label and its application steps

         1、 know tld file

  Click on c Tag we can jump to c.tld In file , and c.tld The document is c Tag library definition profile .

So we want to customize the label , First of all, we need Customize the definition profile of this tag .tld

        2、 .tld Configuration file method ：

                1） newly build .tld file

         2） modify uri label

         3、jsp adopt taglib Instruction import label Library  

Find your own definition uri

 <uri>http://jsp.zhwLouis</uri>

  Next is the custom tag code ：

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
  <%@taglib prefix="z" uri="http://jsp.zhwLouis"%>
<!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>
	<!-- 
	1. Custom label library and tld relevant 
	2. Tags in tag library and tld Medium tag of , Follow tag Element is related to the corresponding helper class 
	 -->
<z:if test="true">true</z:if>
<z:if test="false">false</z:if>
<z:set var="name" value=" Li Si "></z:set>
<z:out value="${name }"></z:out>
</body>
</html>

The operation results are as follows ：

 

         4、 Create helper class

Custom labels above , We just changed uri and short-name, Now it's time to define your own label

                1） Must inherit bodytagSupport

package com.zhw.tag;

import javax.servlet.jsp.JspException;
import javax.servlet.jsp.tagext.BodyTagSupport;

/**
 *  Helper    Must inherit bodytagSupport
 * @author zhw
 *
 */
public class Demo1Tag extends BodyTagSupport{
	@Override
	public int doStartTag() throws JspException {
		System.out.println("============doStartTag=============");
		return super.doStartTag();
	}
	
	@Override
	public int doAfterBody() throws JspException {
		System.out.println("============doAfterBody=============");
		return super.doAfterBody();
	}
	
	@Override
	public int doEndTag() throws JspException {
		System.out.println("============doEndTag=============");
		return super.doEndTag();
	}
}

        5、 change tld In the document tag

<?xml version="1.0" encoding="UTF-8" ?>

<taglib 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 http://java.sun.com/xml/ns/j2ee/web-jsptaglibrary_2_0.xsd"
    version="2.0">
    
  <description>JSTL 1.1 core library</description>
  <display-name>JSTL core</display-name>
  <tlib-version>1.1</tlib-version>
  <short-name>zz</short-name>
  <uri>http://jsp.zhwLouis</uri>

  <validator>
    <validator-class>
        org.apache.taglibs.standard.tlv.JstlCoreTLV
    </validator-class>
  </validator>

  <tag>
    <name>demo</name>
    <tag-class>com.zhw.tag.Demo1Tag</tag-class>
    <body-content>JSP</body-content>
    <attribute>
        <name>var</name>
        <required>false</required>
        <rtexprvalue>false</rtexprvalue>
    </attribute>
  </tag>
</taglib>

Let's try it out ：

 

We are zz There is only one defined in demo So it just shows demo 

3、 ... and 、 Tag life cycle

Four 、 Case study

        1、z:if label

                        Helper 

package com.zhw.tag;

import javax.servlet.jsp.JspException;
import javax.servlet.jsp.tagext.BodyTagSupport;
/**
* if label ：
*  analysis 
	*  If the conditions are met , Just print the label body --->doStartTag The return value of ：EVAL_BODY_INCLUDE
	*  If you don't do that , The label body is not output --->doStartTag The return value of ：SKIP_BODY
*  You need to get the result value of whether the condition is met , Then the tag has an attribute , The property value is boolean
*/
public class IfTag extends BodyTagSupport{
	private boolean test;
	
	public boolean isTest() {
		return test;
	}

	public void setTest(boolean test) {
		this.test = test;
	}


	@Override
	public int doStartTag() throws JspException {
//		 If you don't do that , The label body is not output ->dostarttag The return value of skip_body
//		 You need to get the result set that meets the conditions , Then the tag has an attribute , The property value is boolean
		return test?EVAL_BODY_INCLUDE:SKIP_BODY;
	}

}

         .tld File configuration 

<?xml version="1.0" encoding="UTF-8" ?>

<taglib 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 http://java.sun.com/xml/ns/j2ee/web-jsptaglibrary_2_0.xsd"
    version="2.0">
    
  <description>JSTL 1.1 core library</description>
  <display-name>JSTL core</display-name>
  <tlib-version>1.1</tlib-version>
  <short-name>zz</short-name>
  <uri>http://jsp.zhwLouis</uri>

  <validator>
    <validator-class>
        org.apache.taglibs.standard.tlv.JstlCoreTLV
    </validator-class>
  </validator>

  <tag>
    <name>demo</name>
    <tag-class>com.zhw.tag.Demo1Tag</tag-class>
    <body-content>JSP</body-content>
    <attribute>
        <name>var</name>
        <required>false</required>
        <rtexprvalue>false</rtexprvalue>
    </attribute>
  </tag>
  
   <tag>
    <name>if</name>
    <tag-class>com.zhw.tag.IfTag</tag-class>
    <body-content>JSP</body-content>
    <attribute>
        <name>test</name>
        <required>true</required>
        <rtexprvalue>true</rtexprvalue>
    </attribute>
  </tag>
</taglib>

  The trial code is as follows ：

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<%@ taglib uri="http://jsp.zhwLouis" prefix="zz" %>
<!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>
	<zz:if test="true">true</zz:if>
</body>
</html>

give the result as follows ：

        2、z:set label    z:out label

                1、set

Helper ：

package com.zhw.tag;
 
import javax.servlet.jsp.JspException;
import javax.servlet.jsp.tagext.BodyTagSupport;
 
public class SetTag extends BodyTagSupport{
	private String var;
	private Object value;
	
	public String getVar() {
		return var;
	}
 
	public void setVar(String var) {
		this.var = var;
	}
 
	public Object getValue() {
		return value;
	}
 
	public void setValue(Object value) {
		this.value = value;
	}
 
 
	@Override
	public int doStartTag() throws JspException {
//		 To store data , One key value pairs , From analysis , The label has 2 Attributes 
		pageContext.setAttribute(var, value);
		return super.doStartTag();
	}
}

.tld file ：

<?xml version="1.0" encoding="UTF-8" ?>

<taglib 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 http://java.sun.com/xml/ns/j2ee/web-jsptaglibrary_2_0.xsd"
    version="2.0">
    
  <description>JSTL 1.1 core library</description>
  <display-name>JSTL core</display-name>
  <tlib-version>1.1</tlib-version>
  <short-name>zz</short-name>
  <uri>http://jsp.zhwLouis</uri>

  <validator>
    <validator-class>
        org.apache.taglibs.standard.tlv.JstlCoreTLV
    </validator-class>
  </validator>

  <tag>
    <name>demo</name>
    <tag-class>com.zhw.tag.Demo1Tag</tag-class>
    <body-content>JSP</body-content>
    <attribute>
        <name>var</name>
        <required>false</required>
        <rtexprvalue>false</rtexprvalue>
    </attribute>
  </tag>
  
   <tag>
    <name>if</name>
    <tag-class>com.zhw.tag.IfTag</tag-class>
    <body-content>JSP</body-content>
    <attribute>
        <name>test</name>
        <required>true</required>
        <rtexprvalue>true</rtexprvalue>
    </attribute>
  </tag>
  
  <tag>
    <name>set</name>
    <tag-class>com.zhw.tag.SetTag</tag-class>
    <body-content>JSP</body-content>
    <attribute>
        <name>var</name>
        <required>false</required>
        <rtexprvalue>false</rtexprvalue>
    </attribute>
    <attribute>
        <name>value</name>
        <required>false</required>
        <rtexprvalue>true</rtexprvalue>
    </attribute>
  </tag>
</taglib>

        2 、out

Helper ：

package com.zhw.tag;
 
import java.io.IOException;
 
import javax.servlet.jsp.JspException;
import javax.servlet.jsp.JspWriter;
import javax.servlet.jsp.tagext.BodyTagSupport;
 
public class OutTag extends BodyTagSupport {
	private Object value;
	 
	public Object getValue() {
		return value;
	}
 
	public void setValue(Object value) {
		this.value = value;
	}
	
	@Override
	public int doStartTag() throws JspException {
		JspWriter out = pageContext.getOut();
		try {
			out.print(value);
		} catch (IOException e) {
			e.printStackTrace();
		}
		return super.doStartTag();
	}
	
 
}

.tld file ：

<?xml version="1.0" encoding="UTF-8" ?>

<taglib 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 http://java.sun.com/xml/ns/j2ee/web-jsptaglibrary_2_0.xsd"
    version="2.0">
    
  <description>JSTL 1.1 core library</description>
  <display-name>JSTL core</display-name>
  <tlib-version>1.1</tlib-version>
  <short-name>zz</short-name>
  <uri>http://jsp.zhwLouis</uri>

  <validator>
    <validator-class>
        org.apache.taglibs.standard.tlv.JstlCoreTLV
    </validator-class>
  </validator>

  <tag>
    <name>demo</name>
    <tag-class>com.zhw.tag.Demo1Tag</tag-class>
    <body-content>JSP</body-content>
    <attribute>
        <name>var</name>
        <required>false</required>
        <rtexprvalue>false</rtexprvalue>
    </attribute>
  </tag>
  
   <tag>
    <name>if</name>
    <tag-class>com.zhw.tag.IfTag</tag-class>
    <body-content>JSP</body-content>
    <attribute>
        <name>test</name>
        <required>true</required>
        <rtexprvalue>true</rtexprvalue>
    </attribute>
  </tag>
  
  <tag>
    <name>set</name>
    <tag-class>com.zhw.tag.SetTag</tag-class>
    <body-content>JSP</body-content>
    <attribute>
        <name>var</name>
        <required>false</required>
        <rtexprvalue>false</rtexprvalue>
    </attribute>
    <attribute>
        <name>value</name>
        <required>false</required>
        <rtexprvalue>true</rtexprvalue>
    </attribute>
  </tag>
  
   <tag>
    <name>out</name>
    <tag-class>com.zhw.tag.OutTag</tag-class>
    <body-content>JSP</body-content>
    <attribute>
        <name>value</name>
        <required>true</required>
        <rtexprvalue>true</rtexprvalue>
    </attribute>
  </tag>
</taglib>

Trial code ：

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<%@ taglib uri="http://jsp.zhwLouis" prefix="zz" %>
<!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>
	<zz:if test="true">true</zz:if>
	<zz:set var="name" value=" Zhang San "></zz:set>
	<zz:out value="${name }"></zz:out>
</body>
</html>

give the result as follows ：

 

summary

The content shared this time is the basis of custom tag library , I hope it can help you , In the next issue, the user-defined label library will be enhanced .

I'm nine songs , A programmer who likes programming .

If there is any mistake, please correct it , Thank you very much! .

原网站

版权声明
本文为[An Li Jiu Ge]所创，转载请带上原文链接，感谢
https://yzsam.com/2022/174/202206230839534164.html

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