org.apache.taglibs.standard.tag.common.core.ChooseTag Maven / Gradle / Ivy
/*
* The contents of this file are subject to the terms
* of the Common Development and Distribution License
* (the "License"). You may not use this file except
* in compliance with the License.
*
* You can obtain a copy of the license at
* glassfish/bootstrap/legal/CDDLv1.0.txt or
* https://glassfish.dev.java.net/public/CDDLv1.0.html.
* See the License for the specific language governing
* permissions and limitations under the License.
*
* When distributing Covered Code, include this CDDL
* HEADER in each file and include the License file at
* glassfish/bootstrap/legal/CDDLv1.0.txt. If applicable,
* add the following below this CDDL HEADER, with the
* fields enclosed by brackets "[]" replaced with your
* own identifying information: Portions Copyright [yyyy]
* [name of copyright owner]
*
* Copyright 2005 Sun Microsystems, Inc. All rights reserved.
*
* Portions Copyright Apache Software Foundation.
*/
package org.apache.taglibs.standard.tag.common.core;
import javax.servlet.jsp.JspException;
import javax.servlet.jsp.tagext.TagSupport;
import org.apache.taglibs.standard.resources.Resources;
/**
* Tag handler for <choose> in JSTL.
*
* <choose> is a very simple tag that acts primarily as a container;
* it always includes its body and allows exactly one of its child
* <when> tags to run. Since this tag handler doesn't have any
* attributes, it is common.core to both the rtexprvalue and expression-
* evaluating versions of the JSTL library.
*
* @author Shawn Bayern
*/
public class ChooseTag extends TagSupport {
//*********************************************************************
// Constructor and lifecycle management
// initialize inherited and local state
public ChooseTag() {
super();
init();
}
// Releases any resources we may have (or inherit)
public void release() {
super.release();
init();
}
//*********************************************************************
// Private state
private boolean subtagGateClosed; // has one subtag already executed?
//*********************************************************************
// Public methods implementing exclusivity checks
/**
* Returns status indicating whether a subtag should run or not.
*
* @return true if the subtag should evaluate its condition
* and decide whether to run, false otherwise.
*/
public synchronized boolean gainPermission() {
return (!subtagGateClosed);
}
/**
* Called by a subtag to indicate that it plans to evaluate its
* body.
*/
public synchronized void subtagSucceeded() {
if (subtagGateClosed)
throw new IllegalStateException(
Resources.getMessage("CHOOSE_EXCLUSIVITY"));
subtagGateClosed = true;
}
//*********************************************************************
// Tag logic
// always include body
public int doStartTag() throws JspException {
subtagGateClosed = false; // when we start, no children have run
return EVAL_BODY_INCLUDE;
}
//*********************************************************************
// Private utility methods
private void init() {
subtagGateClosed = false; // reset flag
}
}