1 /*
2  * Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
3  *
4  * Licensed under the Apache License, Version 2.0 (the "License").
5  * You may not use this file except in compliance with the License.
6  * A copy of the License is located at
7  *
8  *  http://aws.amazon.com/apache2.0
9  *
10  * or in the "license" file accompanying this file. This file is distributed
11  * on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either
12  * express or implied. See the License for the specific language governing
13  * permissions and limitations under the License.
14  */
15 
16 package software.amazon.awssdk.enhanced.dynamodb;
17 
18 import software.amazon.awssdk.annotations.SdkPublicApi;
19 import software.amazon.awssdk.annotations.ThreadSafe;
20 import software.amazon.awssdk.enhanced.dynamodb.extensions.ReadModification;
21 import software.amazon.awssdk.enhanced.dynamodb.extensions.WriteModification;
22 
23 /**
24  * Interface for extending the DynamoDb Enhanced client. Two hooks are provided, one that is called just before a record
25  * is written to the database, and one called just after a record is read from the database. This gives the extension the
26  * opportunity to act as an invisible layer between the application and the database and transform the data accordingly.
27  * <p>
28  * Multiple extensions can be used with the enhanced client, but the order in which they are loaded is important. For
29  * instance one extension may overwrite the value of an attribute that another extension then includes in a checksum
30  * calculation.
31  */
32 @SdkPublicApi
33 @ThreadSafe
34 public interface DynamoDbEnhancedClientExtension {
35     /**
36      * This hook is called just before an operation is going to write data to the database. The extension that
37      * implements this method can choose to transform the item itself, or add a condition to the write operation
38      * or both.
39      *
40      * @param context The {@link DynamoDbExtensionContext.BeforeWrite} context containing the state of the execution.
41      * @return A {@link WriteModification} object that can alter the behavior of the write operation.
42      */
beforeWrite(DynamoDbExtensionContext.BeforeWrite context)43     default WriteModification beforeWrite(DynamoDbExtensionContext.BeforeWrite context) {
44         return WriteModification.builder().build();
45     }
46 
47     /**
48      * This hook is called just after an operation that has read data from the database. The extension that
49      * implements this method can choose to transform the item, and then it is the transformed item that will be
50      * mapped back to the application instead of the item that was actually read from the database.
51      *
52      * @param context The {@link DynamoDbExtensionContext.AfterRead} context containing the state of the execution.
53      * @return A {@link ReadModification} object that can alter the results of a read operation.
54      */
afterRead(DynamoDbExtensionContext.AfterRead context)55     default ReadModification afterRead(DynamoDbExtensionContext.AfterRead context) {
56         return ReadModification.builder().build();
57     }
58 }
59