Home › JSP custom tags example with body

JSP custom tags example with body 

Fang
Joined:
08/13/2009
Posts:
164

January 28, 2012 13:24:09    Last update: January 28, 2012 13:31:22
This is a simple JSP custom tags library with tag body. Just like the JSF counterpart, it splits a string and repeats the body for each word, i.e., with this markup: 
<%@ taglib uri="http://custom.tag.com/demo" prefix="my"%>
<html>
<body>
<my:iterate var="name" value="Tigger Kanga Roo">
	<p>Hello ${name}!</p>
</my:iterate>
</body>
</html>

output: 
<html>
<body>
	<p>Hello Tigger!</p>
	<p>Hello Kanga!</p>
	<p>Hello Roo!</p>
</body>
</html>

With Maven, this is the directory structure: 
./src
./src/main
./src/main/resources
./src/main/resources/META-INF
./src/main/resources/META-INF/demotag.tld
./src/main/java
./src/main/java/tagdemo
./src/main/java/tagdemo/IterateTag.java
./pom.xml

There are three files to write:
  1. pom.xml: 
    <project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <groupId>tag-demo</groupId>
    <artifactId>jsp-tags</artifactId>
    <packaging>jar</packaging>
    <version>1.0</version>
    <name>JSP Custom tag demo</name>
    <url>http://custom.tag.com</url>

    <dependencies>
	<dependency>
	    <groupId>javax</groupId>
	    <artifactId>javaee-api</artifactId>
	    <version>6.0</version>
	    <scope>provided</scope>
	</dependency>
    </dependencies>
</project>

  2. src/main/java/tagdemo/IterateTag.java: 
    package tagdemo;

import java.io.IOException;

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

public class IterateTag extends BodyTagSupport {
	private String value;
	private String var;
	private String[] vals = null;
	private int index = 0;

	public String getValue() {
		return this.value;
	}

	public void setValue(String value) {
		this.value = value;
		this.vals = value.split("\\s+");
	}

	public String getVar() {
		return this.var;
	}

	public void setVar(String var) {
		this.var = var;
	}

	public int doStartTag() throws JspException {
		if (this.vals.length < 1) {
			return SKIP_BODY;
		}

		pageContext.setAttribute(getVar(), vals[0]);
		this.index = 1;
		return EVAL_BODY_BUFFERED;
	}

	public int doAfterBody() throws JspException {
		if (this.index < this.vals.length) {
			pageContext.setAttribute(getVar(), vals[this.index]);
			this.index++;
			return EVAL_BODY_AGAIN;
		}

		try {
			BodyContent bc = getBodyContent();
			bc.writeOut(getPreviousOut());
		}
		catch (IOException e) {
			throw new JspException(e);
		}

		return SKIP_BODY;
	}
}

  3. src/main/resources/META-INF/demotag.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>cust</short-name>
    <uri>http://custom.tag.com/demo</uri>
    <display-name>Custom Tag Example</display-name>
    <description>Custom tag examples</description>

    <tag>
	<name>iterate</name>
        <tagclass>
            tagdemo.IterateTag
        </tagclass>
        <bodycontent>JSP</bodycontent>
        <description>
            <![CDATA[
            <p><strong>Split a String and repeat body for each</strong></p>
            ]]>
        </description>
        <attribute>
            <name>value</name>
            <required>true</required>
            <rtexprvalue>true</rtexprvalue>
            <description>
                <![CDATA[
                  <p>The String value to split</p>
                  ]]>
            </description>
        </attribute>
        <attribute>
            <name>var</name>
            <required>true</required>
            <rtexprvalue>true</rtexprvalue>
            <description>
                <![CDATA[
                  <p>Name of the variable for each iteration.</p>
                ]]>
            </description>
        </attribute>
    </tag>
</taglib>



Build with: 
mvn clean install


To use it as a dependency in other Maven projects: 
<dependency>
	    <groupId>tag-demo</groupId>
	    <artifactId>jsp-tags</artifactId>
	    <version>1.0</version>
	    <scope>runtime</scope>
</dependency>
Share |
| Comment  | Tags
 

Related Notes