Package jakarta.servlet.jsp.jstl.core

Class ConditionalTagSupport

java.lang.Object

jakarta.servlet.jsp.tagext.TagSupport

jakarta.servlet.jsp.jstl.core.ConditionalTagSupport

All Implemented Interfaces:

IterationTag, JspTag, Tag, Serializable

public abstract class ConditionalTagSupport
extends TagSupport

Abstract class that facilitates implementation of conditional actions where the boolean result is exposed as a JSP scoped variable. The boolean result may then be used as the test condition in a <c:when> action.

This base class provides support for:

• Conditional processing of the action's body based on the returned value of the abstract method condition().
• Storing the result of condition() as a Boolean object into a JSP scoped variable identified by attributes var and scope.

Author:

Shawn Bayern

See Also:

• Serialized Form

Field Summary

Fields inherited from class jakarta.servlet.jsp.tagext.TagSupport

id, pageContext

Fields inherited from interface jakarta.servlet.jsp.tagext.IterationTag

EVAL_BODY_AGAIN

Fields inherited from interface jakarta.servlet.jsp.tagext.Tag

EVAL_BODY_INCLUDE, EVAL_PAGE, SKIP_BODY, SKIP_PAGE

Constructor Summary

Constructors

Constructor	Description
ConditionalTagSupport()	Base constructor to initialize local state.

Method Summary

Modifier and Type	Method	Description
protected abstract boolean	condition()	Subclasses implement this method to compute the boolean result of the conditional action.
int	doStartTag()	Includes its body if condition() evaluates to true.
void	release()	Releases any resources this ConditionalTagSupport may have (or inherit).
void	setScope(String scope)	Sets the 'scope' attribute.
void	setVar(String var)	Sets the 'var' attribute.

Methods inherited from class jakarta.servlet.jsp.tagext.TagSupport

doAfterBody, doEndTag, findAncestorWithClass, getId, getParent, getValue, getValues, removeValue, setId, setPageContext, setParent, setValue

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Details

ConditionalTagSupport

public ConditionalTagSupport()

Base constructor to initialize local state. As with TagSupport, subclasses should not implement constructors with arguments, and no-argument constructors implemented by subclasses must call the superclass constructor.

Method Details

condition

protected abstract boolean condition()
                              throws JspTagException

Subclasses implement this method to compute the boolean result of the conditional action. This method is invoked once per tag invocation by doStartTag().

Returns:

a boolean representing the condition that a particular subclass uses to drive its conditional logic.

Throws:

JspTagException - on failure

doStartTag

public int doStartTag()
               throws JspException

Includes its body if condition() evaluates to true.

Specified by:

doStartTag in interface Tag

Overrides:

doStartTag in class TagSupport

Returns:

SKIP_BODY

Throws:

JspException - if an error occurs while processing this tag

See Also:

• Tag.doStartTag()

release

public void release()

Releases any resources this ConditionalTagSupport may have (or inherit).

Specified by:

release in interface Tag

Overrides:

release in class TagSupport

See Also:

• Tag.release()

setVar

public void setVar(String var)

Sets the 'var' attribute.

Parameters:

var - Name of the exported scoped variable storing the result of condition().

setScope

public void setScope(String scope)

Sets the 'scope' attribute.

Parameters:

scope - Scope of the 'var' attribute