_br-ode-1.X.svn/bpel-runtime/src/main/java/org/apache/ode/bpel/intercept/ThrottlingInterceptor.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.ode.bpel.intercept;

import org.apache.ode.bpel.iapi.MyRoleMessageExchange;
import org.w3c.dom.Node;
import org.w3c.dom.Text;

import javax.xml.namespace.QName;
import java.util.Map;

/**
 * An example of a  simple interceptor providing a "throttling"  capability - that is an 
 * ability to limit the number of instances created for a given process.
 * 
 * @author Maciej Szefler
 */
public class ThrottlingInterceptor extends NoOpInterceptor {
    /** Name of process property that control the maximum number of instances. */
    private static final QName PROP_MAX_INSTANCES = new QName("urn:org.apache.ode.bpel.intercept", "maxInstances");

    @Override
    public void onNewInstanceInvoked(MyRoleMessageExchange mex,
                                     InterceptorContext ic) throws FailMessageExchangeException {
        int maxInstances;
        try {
            maxInstances = Integer.valueOf(getSimpleProperty(PROP_MAX_INSTANCES, ic));
        } catch (Exception ex) {
            return;
        }

        if (ic.getProcessDAO().getNumInstances() >= maxInstances)
            throw new FailMessageExchangeException("Too many instances.");
    }


    /**
     * Get the value of a simple process property
     * @param propertyName name of the property
     * @param ic interceptor context
     * @return value of the property, or <code>null</code> if not set
     */
    private String getSimpleProperty(QName propertyName, InterceptorContext ic) {
        Map<QName, Node> props =  ic.getProcessConf().getProcessProperties();
        for (Map.Entry<QName, Node> prop : props.entrySet()) {
            if (prop.getKey().equals(propertyName))
                return ((Text)prop.getValue()).getWholeText();
        }
        return null;
    }
}