User-defined tags are known as custom tags. In this section we will see how to create a custom tag and use it in JSP.
To create a custom tag we need three things:
1) Tag handler class: In this class we specify what our custom tag will do when
it is used in a JSP page.
2) TLD file: Tag descriptor file where we will specify our tag name, tag handler
class and tag attributes.
3) JSP page: A JSP page where we will be using our custom tag.
Example:
In the below example we are creating a custom tag Myindia which will display the
message “This is my india†when used in a JSP page.
Tag handler class:
A tag handler class should implement Tag/IterationTag/ BodyTag interface or it can also extend TagSupport/BodyTagSupport/SimpleTagSupport class. All the classes that support custom tags are present inside javax.servlet.jsp.tagext. In the below we are extending the class SimpleTagSupport.
example:
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test.java package jsptest.com; import javax.servlet.jsp.tagext.*; import javax.servlet.jsp.*; import java.io.*; public class Details extends Simplecustomtest { public void doTag() throws JspException, IOException { /*This is just to display a message, when * we will use our custom tag. This message * would be displayed JspWriter out = getJspContext().getOut(); out.println("This is my india");}} |
TLD File:
This file should present at the location: Project Name/WebContent/WEB-INF/ and
it should have a .tld extension.
Note:
example:
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note.tld <short-name>My Custom testshort-name> |
Using custom tag in JSP:
Above we have created a custom tag named
Myindia. Here we will be using it.
Note: taglib directive should have the TLD file path in uri field. Above we have
created the note.tld file so we have given the path of that file.
Choose any prefix and specify it in taglib directive’s prefix field. Here we
have specified it as myprefix.
Custom tag is called like this:
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<%@ taglib prefix="myprefix" uri="WEB-INF/note.tld"%> |