org.apache.taglibs.standard.tag.el.core.WhenTag Maven / Gradle / Ivy

Show more of this group Show more artifacts with this name
Show all versions of jakarta.servlet.jsp.jstl Show documentation

Jakarta Standard Tag Library Implementation

There is a newer version: 3.0.1

Show newest version

/*
 * Copyright (c) 1997-2020 Oracle and/or its affiliates. All rights reserved.
 * Copyright 2004 The Apache Software Foundation
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.taglibs.standard.tag.el.core;

import jakarta.servlet.jsp.JspException;
import jakarta.servlet.jsp.JspTagException;

import org.apache.taglibs.standard.lang.support.ExpressionEvaluatorManager;
import org.apache.taglibs.standard.tag.common.core.NullAttributeException;
import org.apache.taglibs.standard.tag.common.core.WhenTagSupport;

/**
 * Tag handler for <when> in JSTL's expression-evaluating
 * library.
 *
 * @author Shawn Bayern
 */

public class WhenTag extends WhenTagSupport {

    //*********************************************************************
    // Constructor and lifecycle management

    // initialize inherited and local state
    public WhenTag() {
        super();
        init();
    }

    // Releases any resources we may have (or inherit)
    public void release() {
        super.release();
        init();
    }


    //*********************************************************************
    // Supplied conditional logic

    protected boolean condition() throws JspTagException {
        try { 
            Object r = ExpressionEvaluatorManager.evaluate(
                "test", test, Boolean.class, this, pageContext);
            if (r == null)
	        throw new NullAttributeException("when", "test");
            else
                return (((Boolean) r).booleanValue());
	} catch (JspException ex) {
	    throw new JspTagException(ex.toString(), ex);
	}
    }


    //*********************************************************************
    // Private state

    private String test;               // the value of the 'test' attribute


    //*********************************************************************
    // Accessors

    // receives the tag's 'test' attribute
    public void setTest(String test) {
        this.test = test;
    }


    //*********************************************************************
    // Private utility methods

    // resets internal state
    private void init() {
        test = null;
    }
}