vmreferencemungevisitor.java

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package org.apache.velocity.runtime.visitor;

/*
 * 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 java.util.Map;

import org.apache.velocity.runtime.parser.node.ASTReference;

/**
 *  This class is a visitor used by the VM proxy to change the
 *  literal representation of a reference in a VM.  The reason is
 *  to preserve the 'render literal if null' behavior w/o making
 *  the VMProxy stuff more complicated than it is already.
 *
 * @author <a href="mailto:[e-mail]">Geir Magnusson Jr.</a>
 * @version $Id: VMReferenceMungeVisitor.java 463298 2006-10-12 16:10:32Z henning $
 */
public class VMReferenceMungeVisitor extends BaseVisitor
{
    /**
     *  Map containing VM arg to instance-use reference
     *  Passed in with CTOR
     */
    private Map argmap = null;

    /**
     *  CTOR - takes a map of args to reference
     * @param map
     */
    public VMReferenceMungeVisitor( Map map )
    {
        argmap = map;
    }

    /**
     *  Visitor method - if the literal is right, will
     *  set the literal in the ASTReference node
     *
     *  @param node ASTReference to work on
     *  @param data Object to pass down from caller
     * @return A visitor object result.
     */
    public Object visit( ASTReference node, Object data)
    {
        /*
         *  see if there is an override value for this
         *  reference
         */
        String override = (String) argmap.get( node.literal().substring(1) );

        /*
         *  if so, set in the node
         */
        if( override != null)
        {
            node.setLiteral( override );
        }

        /*
         *  feed the children...
         */
        data = node.childrenAccept(this, data);

        return data;
    }
}