fix: create clients only if necessary (#187)

Author: imabhichow

src/main/java/software/amazon/encryption/s3/S3AsyncEncryptionClient.java

@@ -251,7 +251,7 @@ public void close() {
     // This is very similar to the S3EncryptionClient builder
     // Make sure to keep both clients in mind when adding new builder options
     public static class Builder {
-        private S3AsyncClient _wrappedClient = S3AsyncClient.builder().build();
+        private S3AsyncClient _wrappedClient;
         private CryptographicMaterialsManager _cryptoMaterialsManager;
         private Keyring _keyring;
         private SecretKey _aesKey;
@@ -507,6 +507,10 @@ public S3AsyncEncryptionClient build() {
                 _bufferSize = DEFAULT_BUFFER_SIZE_BYTES;
             }
 
+            if (_wrappedClient == null) {
+                _wrappedClient = S3AsyncClient.create();
+            }
+
             if (_keyring == null) {
                 if (_aesKey != null) {
                     _keyring = AesKeyring.builder()

src/main/java/software/amazon/encryption/s3/materials/KmsKeyring.java

@@ -230,7 +230,7 @@ protected Map<String, DecryptDataKeyStrategy> decryptDataKeyStrategies() {
     }
 
     public static class Builder extends S3Keyring.Builder<KmsKeyring, Builder> {
-        private KmsClient _kmsClient = KmsClient.builder().build();
+        private KmsClient _kmsClient;
         private String _wrappingKeyId;
 
         private Builder() {
@@ -258,6 +258,10 @@ public Builder wrappingKeyId(String wrappingKeyId) {
         }
 
         public KmsKeyring build() {
+            if (_kmsClient == null) {
+                _kmsClient = KmsClient.create();
+            }
+
             return new KmsKeyring(this);
         }
     }