storm-client/src/jvm/org/apache/storm/trident/operation/Filter.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.trident.operation;

import java.util.Map;
import org.apache.storm.trident.tuple.TridentTuple;

/**
 * Filters take in a tuple as input and decide whether or not to keep that tuple or not.
 *
 * <p>If the `isKeep()` method of a Filter returns `false` for a tuple, that tuple will be filtered out of the Stream
 *
 *
 * <p>### Configuration If your `Filter` implementation has configuration requirements, you will typically want to extend {@link
 * org.apache.storm.trident.operation.BaseFilter} and override the {@link org.apache.storm.trident.operation.Operation#prepare(Map,
 * TridentOperationContext)} method to perform your custom initialization.
 *
 * @see org.apache.storm.trident.Stream
 */
public interface Filter extends EachOperation {

    /**
     * Determines if a tuple should be filtered out of a stream.
     *
     * @param tuple the tuple being evaluated
     * @return `false` to drop the tuple, `true` to keep the tuple
     */
    boolean isKeep(TridentTuple tuple);
}