DATAES-746 - Add store converters to convert binary data.

Original PR: spring-projects#394

Author: sothawo

src/main/java/org/springframework/data/elasticsearch/core/convert/ElasticsearchCustomConversions.java

@@ -17,6 +17,7 @@
 
 import java.math.BigDecimal;
 import java.util.ArrayList;
+import java.util.Base64;
 import java.util.Collection;
 import java.util.Collections;
 import java.util.List;
@@ -48,6 +49,8 @@ public class ElasticsearchCustomConversions extends CustomConversions {
 		converters.add(UUIDToStringConverter.INSTANCE);
 		converters.add(BigDecimalToDoubleConverter.INSTANCE);
 		converters.add(DoubleToBigDecimalConverter.INSTANCE);
+		converters.add(ByteArrayToBase64Converter.INSTANCE);
+		converters.add(Base64ToByteArrayConverter.INSTANCE);
 
 		STORE_CONVERTERS = Collections.unmodifiableList(converters);
 		STORE_CONVERSIONS = StoreConversions.of(ElasticsearchSimpleTypes.HOLDER, STORE_CONVERTERS);
@@ -117,4 +120,36 @@ public Double convert(BigDecimal source) {
 			return NumberUtils.convertNumberToTargetClass(source, Double.class);
 		}
 	}
+
+	/**
+	 * {@link Converter} to write a byte[] to a base64 encoded {@link String} value.
+	 * 
+	 * @since 4.0
+	 */
+	@WritingConverter
+	enum ByteArrayToBase64Converter implements Converter<byte[], String> {
+
+		INSTANCE,;
+
+		@Override
+		public String convert(byte[] source) {
+			return Base64.getEncoder().encodeToString(source);
+		}
+	}
+
+	/**
+	 * {@link Converter} to read a byte[] from a base64 encoded {@link String} value.
+	 * 
+	 * @since 4.0
+	 */
+	@ReadingConverter
+	enum Base64ToByteArrayConverter implements Converter<String, byte[]> {
+
+		INSTANCE;
+
+		@Override
+		public byte[] convert(String source) {
+			return Base64.getDecoder().decode(source);
+		}
+	}
 }

src/test/java/org/springframework/data/elasticsearch/core/convert/ElasticsearchCustomConversionsTest.java

@@ -0,0 +1,40 @@
+/*
+ * Copyright 2020 the original author or authors.
+ *
+ * Licensed 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
+ *
+ *      https://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.springframework.data.elasticsearch.core.convert;
+
+import static org.assertj.core.api.Assertions.*;
+
+import org.junit.jupiter.api.Test;
+import org.springframework.data.elasticsearch.core.convert.ElasticsearchCustomConversions.Base64ToByteArrayConverter;
+import org.springframework.data.elasticsearch.core.convert.ElasticsearchCustomConversions.ByteArrayToBase64Converter;
+
+/**
+ * @author Peter-Josef Meisch
+ */
+class ElasticsearchCustomConversionsTest {
+
+	private byte[] bytes = new byte[] { 0x01, 0x02, 0x03, 0x04 };
+	private String base64 = "AQIDBA==";
+
+	void shouldConvertFromByteArrayToBase64() {
+		assertThat(ByteArrayToBase64Converter.INSTANCE.convert(bytes)).isEqualTo(base64);
+	}
+
+	@Test
+	void shouldConvertFromStringToBase64() {
+		assertThat(Base64ToByteArrayConverter.INSTANCE.convert(base64)).isEqualTo(bytes);
+	}
+}