external/storm-cassandra/src/main/java/org/apache/storm/cassandra/context/BaseBeanFactory.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.storm.cassandra.context;

import java.util.Map;

/**
 * Base BeanProvider implementation.
 */
public abstract class BaseBeanFactory<T> implements BeanFactory<T> {

    protected WorkerCtx context;

    protected volatile T instance;

    /**
     * {@inheritDoc}
     */
    @Override
    public void setStormContext(WorkerCtx context) {
        this.context = context;
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public synchronized T get(Map<String, Object> topoConf) {
        if (instance != null) {
            return instance;
        }
        return instance = make(topoConf);
    }

    /**
     * Return a new instance of T.
     */
    protected abstract T make(Map<String, Object> topoConf);

    /**
     * {@inheritDoc}
     */
    @Override
    public BeanFactory<T> newInstance() {
        Class<? extends BaseBeanFactory> clazz = this.getClass();
        try {
            BaseBeanFactory factory = clazz.newInstance();
            factory.setStormContext(this.context);
            return factory;
        } catch (IllegalAccessException | InstantiationException e) {
            throw new RuntimeException("Cannot create a new instance of " + clazz.getSimpleName(), e);
        }
    }
}