RC9/qpid/java/client/src/main/java/org/apache/qpid/filter/LogicExpression.java

/* 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.
 */
package org.apache.qpid.filter;

import org.apache.qpid.QpidException;
import org.apache.qpid.client.message.AbstractJMSMessage;


/**
 * A filter performing a comparison of two objects
 */
public abstract class LogicExpression extends BinaryExpression implements BooleanExpression
{

    public static BooleanExpression createOR(BooleanExpression lvalue, BooleanExpression rvalue)
    {
        return new LogicExpression(lvalue, rvalue)
            {

                public Object evaluate(AbstractJMSMessage message) throws QpidException
                {

                    Boolean lv = (Boolean) left.evaluate(message);
                    // Can we do an OR shortcut??
                    if ((lv != null) && lv.booleanValue())
                    {
                        return Boolean.TRUE;
                    }

                    Boolean rv = (Boolean) right.evaluate(message);

                    return (rv == null) ? null : rv;
                }

                public String getExpressionSymbol()
                {
                    return "OR";
                }
            };
    }

    public static BooleanExpression createAND(BooleanExpression lvalue, BooleanExpression rvalue)
    {
        return new LogicExpression(lvalue, rvalue)
            {

                public Object evaluate(AbstractJMSMessage message) throws QpidException
                {

                    Boolean lv = (Boolean) left.evaluate(message);

                    // Can we do an AND shortcut??
                    if (lv == null)
                    {
                        return null;
                    }

                    if (!lv.booleanValue())
                    {
                        return Boolean.FALSE;
                    }

                    Boolean rv = (Boolean) right.evaluate(message);

                    return (rv == null) ? null : rv;
                }

                public String getExpressionSymbol()
                {
                    return "AND";
                }
            };
    }

    /**
     * @param left
     * @param right
     */
    public LogicExpression(BooleanExpression left, BooleanExpression right)
    {
        super(left, right);
    }

    public abstract Object evaluate(AbstractJMSMessage message) throws QpidException;

    public boolean matches(AbstractJMSMessage message) throws QpidException
    {
        Object object = evaluate(message);

        return (object != null) && (object == Boolean.TRUE);
    }

}