velocity-engine-core/src/main/java/org/apache/velocity/runtime/parser/node/ASTOrNode.java

package org.apache.velocity.runtime.parser.node;

/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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.
 */

import org.apache.velocity.context.InternalContextAdapter;
import org.apache.velocity.exception.MethodInvocationException;
import org.apache.velocity.runtime.parser.Parser;

/**
 * Please look at the Parser.jjt file which is
 * what controls the generation of this class.
 *
 * @author <a href="mailto:jvanzyl@apache.org">Jason van Zyl</a>
 * @author <a href="mailto:geirm@optonline.net">Geir Magnusson Jr.</a>
 * @version $Id$
*/
public class ASTOrNode extends ASTLogicalOperator
{
    /**
     * @param id
     */
    public ASTOrNode(int id)
    {
        super(id);
    }

    /**
     * @param p
     * @param id
     */
    public ASTOrNode(Parser p, int id)
    {
        super(p, id);
    }

    @Override
    public String getLiteralOperator()
    {
        return "||";
    }

    /**
     * @see org.apache.velocity.runtime.parser.node.SimpleNode#jjtAccept(org.apache.velocity.runtime.parser.node.ParserVisitor, java.lang.Object)
     */
    public Object jjtAccept(ParserVisitor visitor, Object data)
    {
        return visitor.visit(this, data);
    }

    /**
     *  Returns the value of the expression.
     *  Since the value of the expression is simply the boolean
     *  result of evaluate(), lets return that.
     * @param context
     * @return The Expression value.
     * @throws MethodInvocationException
     */
    public Object value(InternalContextAdapter context )
        throws MethodInvocationException
    {
        return evaluate(context) ? Boolean.TRUE : Boolean.FALSE;
    }

    /**
     *  the logical or :
     *    <pre>
     *      left || null -&gt; left
     *      null || right -&gt; right
     *      null || null -&gt; false
     *      left || right -&gt;  left || right
     *    </pre>
     * @param context
     * @return The evaluation result.
     * @throws MethodInvocationException
     */
    public boolean evaluate( InternalContextAdapter context)
        throws MethodInvocationException
    {
        Node left = jjtGetChild(0);
        Node right = jjtGetChild(1);

        /*
         *  if the left is not null and true, then true
         */

        if (left != null && left.evaluate( context ) )
            return true;

        /*
         *  same for right
         */

        return right != null && right.evaluate(context);
    }
}