Adding a simple example of data key caching

src/examples/java/com/amazonaws/crypto/examples/datakeycaching/SimpleDataKeyCachingExample.java

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+/*
+ * Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"). You may not use this file except
+ * in compliance with the License. A copy of the License is located at
+ *
+ * http://aws.amazon.com/apache2.0
+ *
+ * or in the "license" file accompanying this file. This file 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 com.amazonaws.crypto.examples.datakeycaching;
+
+import com.amazonaws.encryptionsdk.AwsCrypto;
+import com.amazonaws.encryptionsdk.CryptoMaterialsManager;
+import com.amazonaws.encryptionsdk.EncryptRequest;
+import com.amazonaws.encryptionsdk.caching.CachingCryptoMaterialsManager;
+import com.amazonaws.encryptionsdk.caching.CryptoMaterialsCache;
+import com.amazonaws.encryptionsdk.caching.LocalCryptoMaterialsCache;
+import com.amazonaws.encryptionsdk.keyrings.Keyring;
+import com.amazonaws.encryptionsdk.keyrings.StandardKeyrings;
+import com.amazonaws.encryptionsdk.kms.AwsKmsCmkId;
+
+import java.nio.charset.StandardCharsets;
+import java.util.Collections;
+import java.util.Map;
+import java.util.concurrent.TimeUnit;
+
+/**
+ * <p>
+ * Encrypts a string using an AWS KMS customer master key (CMK) and data key caching
+ *
+ * <p>
+ * Arguments:
+ * <ol>
+ * <li>KMS CMK ARN: To find the Amazon Resource Name of your AWS KMS customer master key (CMK),
+ *     see 'Viewing Keys' at http://docs.aws.amazon.com/kms/latest/developerguide/viewing-keys.html
+ * </ol>
+ */
+public class SimpleDataKeyCachingExample {
+
+    /*
+     *  The maximum number of data keys in the cache (required).
+     *  When the cache is full, the oldest entry is evicted to
+     *  make room for a newer one.
+     */
+    private static final int CAPACITY = 10;
+
+    /*
+     *  The maximum number of messages encrypted under a single data key.
+     *  This value is optional, but you should configure the lowest practical value.
+     */
+    private static final int MAX_ENTRY_MESSAGES = 100;
+
+    /*
+     *  The time in seconds that an entry is cached (required).
+     *  The cache actively removes entries that have exceeded the thresholds.
+     */
+    private static final int MAX_ENTRY_AGE_IN_SECONDS = 60;
+
+    /*
+     *  Example data to encrypt
+     */
+    private static final byte[] EXAMPLE_DATA = "Hello World".getBytes(StandardCharsets.UTF_8);
+
+    public static void main(final String[] args) {
+        encryptWithCaching(AwsKmsCmkId.fromString(args[0]));
+    }
+
+    static byte[] encryptWithCaching(AwsKmsCmkId kmsCmkArn) {
+
+        // Instantiate the SDK
+        final AwsCrypto crypto = new AwsCrypto();
+
+        // Create an encryption context
+        final Map<String, String> encryptionContext = Collections.singletonMap("purpose", "test");
+
+        // Create a keyring
+        final Keyring keyring = StandardKeyrings.awsKms(kmsCmkArn);
+
+        // Create a cache
+        final CryptoMaterialsCache cache = new LocalCryptoMaterialsCache(CAPACITY);
+
+        // Create a caching CMM
+        final CryptoMaterialsManager cachingCmm =
+                CachingCryptoMaterialsManager.newBuilder()
+                        .withKeyring(keyring)
+                        .withCache(cache)
+                        .withMaxAge(MAX_ENTRY_AGE_IN_SECONDS, TimeUnit.SECONDS)
+                        .withMessageUseLimit(MAX_ENTRY_MESSAGES)
+                        .build();
+
+        // When the call to encrypt specifies a caching CMM,
+        // the encryption operation uses the data key cache
+        return crypto.encrypt(EncryptRequest.builder()
+                .cryptoMaterialsManager(cachingCmm)
+                .plaintext(EXAMPLE_DATA)
+                .encryptionContext(encryptionContext)
+                .build()).getResult();
+    }
+}

src/test/java/com/amazonaws/crypto/examples/datakeycaching/SimpleDataKeyCachingExampleTest.java

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+/*
+ * Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"). You may not use this file except
+ * in compliance with the License. A copy of the License is located at
+ *
+ * http://aws.amazon.com/apache2.0
+ *
+ * or in the "license" file accompanying this file. This file 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 com.amazonaws.crypto.examples.datakeycaching;
+
+import com.amazonaws.encryptionsdk.TestUtils;
+import com.amazonaws.encryptionsdk.kms.AwsKmsCmkId;
+import com.amazonaws.encryptionsdk.kms.KMSTestFixtures;
+import org.junit.jupiter.api.Tag;
+import org.junit.jupiter.api.Test;
+
+@Tag(TestUtils.TAG_INTEGRATION)
+class SimpleDataKeyCachingExampleTest {
+
+    @Test
+    void testEncryptWithCaching() {
+        SimpleDataKeyCachingExample.encryptWithCaching(AwsKmsCmkId.fromString(KMSTestFixtures.TEST_KEY_IDS[0]));
+    }
+}