external/storm-cassandra/src/main/java/org/apache/storm/cassandra/query/ContextQuery.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.query;

import org.apache.storm.tuple.ITuple;

import java.io.Serializable;
import java.util.Map;

/**
 * This interface may be used to retrieve a cassandra bound query either from storm config
 * or the tuple being proceed.
 *
 */
public interface ContextQuery extends Serializable {

    /**
     * Resolves a cassandra bound query.
     *
     * @param config the storm configuration
     * @param tuple the tuple being proceed.
     *
     * @return a string bound query.
     */
    public String resolves(Map config, ITuple tuple);

    /**
     * Static implementation of {@link ContextQuery} interface.
     */
    public static final class StaticContextQuery implements ContextQuery {
        private final String value;

        /**
         * Creates a new {@link StaticContextQuery} instance.
         * @param value
         */
        public StaticContextQuery(String value) {
            this.value = value;
        }

        @Override
        public String resolves(Map config, ITuple tuple) {
            return value;
        }
    }

    /**
     * Default {@link BoundQueryContext} implementation to retrieve a bound query
     * identified by the provided key.
     */
    public static final class BoundQueryContext implements ContextQuery {
        private String key;

        public BoundQueryContext(String key) {
            this.key = key;
        }

        @Override
        public String resolves(Map config, ITuple tuple) {
            if (config.containsKey(key)) return (String) config.get(key);

            throw new IllegalArgumentException("Bound query '" + key + "' does not exist in configuration");
        }
    }

    /**
     * Default {@link BoundQueryNamedByFieldContext} implementation to retrieve a bound query named by
     * the value of a specified tuple field.
     */
    public static final class BoundQueryNamedByFieldContext implements ContextQuery {

        private String fieldName;

        public BoundQueryNamedByFieldContext(String fieldName) {
            this.fieldName = fieldName;
        }

        @Override
        public String resolves(Map config, ITuple tuple) {
            String name = tuple.getStringByField(fieldName);
            if (config.containsKey(name)) return (String) config.get(name);
            throw new IllegalArgumentException("Bound query '" + name + "' does not exist in configuration");
        }
    }
}