fc38177ae173bb2c5d161be05ecc7ce4afe7cc36
[samza.git] / samza-api / src / main / java / org / apache / samza / operators / functions / JoinFunction.java
1 /*
2 * Licensed to the Apache Software Foundation (ASF) under one
3 * or more contributor license agreements. See the NOTICE file
4 * distributed with this work for additional information
5 * regarding copyright ownership. The ASF licenses this file
6 * to you under the Apache License, Version 2.0 (the
7 * "License"); you may not use this file except in compliance
8 * with the License. You may obtain a copy of the License at
9 *
10 * http://www.apache.org/licenses/LICENSE-2.0
11 *
12 * Unless required by applicable law or agreed to in writing,
13 * software distributed under the License is distributed on an
14 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
15 * KIND, either express or implied. See the License for the
16 * specific language governing permissions and limitations
17 * under the License.
18 */
19 package org.apache.samza.operators.functions;
20
21 import org.apache.samza.annotation.InterfaceStability;
22
23
24 /**
25 * A function that joins messages from two {@link org.apache.samza.operators.MessageStream}s and produces
26 * a joined message.
27 * @param <K> type of the join key
28 * @param <M> type of the input message
29 * @param <JM> type of the message to join with
30 * @param <RM> type of the joined message
31 */
32 @InterfaceStability.Unstable
33 public interface JoinFunction<K, M, JM, RM> extends InitableFunction {
34
35 /**
36 * Join the provided input messages and produces the joined messages.
37 * @param message the input message
38 * @param otherMessage the message to join with
39 * @return the joined message
40 */
41 RM apply(M message, JM otherMessage);
42
43 /**
44 * Method to get the join key in the messages from the first input stream
45 *
46 * @param message the input message from the first input stream
47 * @return the join key
48 */
49 K getFirstKey(M message);
50
51 /**
52 * Method to get the join key in the messages from the second input stream
53 *
54 * @param message the input message from the second input stream
55 * @return the join key
56 */
57 K getSecondKey(JM message);
58
59 }