DATAJPA-506 - Add support for conversion of Blob values to byte[] in native queries.

JpaQueryExecution no applies type conversion for Blob instances to be able to return byte[] from repository calls.

Original pull request: #72.

src/main/java/org/springframework/data/jpa/repository/query/JpaQueryExecution.java

@@ -24,6 +24,7 @@ import javax.persistence.Query;
 import javax.persistence.StoredProcedureQuery;
 import javax.persistence.TypedQuery;
 
+import org.springframework.core.convert.support.DefaultConversionService;
 import org.springframework.data.domain.PageImpl;
 import org.springframework.data.domain.Pageable;
 import org.springframework.data.domain.Slice;
@@ -43,6 +44,12 @@ import org.springframework.util.Assert;
  */
 public abstract class JpaQueryExecution {
 
+	private static final DefaultConversionService conversionService = new DefaultConversionService();
+
+	static {
+		conversionService.addConverter(JpaResultConverters.BlobToByteArrayConverter.INSTANCE);
+	}
+
 	/**
 	 * Executes the given {@link AbstractStringBasedJpaQuery} with the given {@link ParameterBinder}.
 	 * 
@@ -55,11 +62,26 @@ public abstract class JpaQueryExecution {
 		Assert.notNull(query);
 		Assert.notNull(values);
 
+		Object result;
+
 		try {
-			return doExecute(query, values);
+			result = doExecute(query, values);
 		} catch (NoResultException e) {
 			return null;
 		}
+
+		if (result == null) {
+			return null;
+		}
+
+		JpaQueryMethod queryMethod = query.getQueryMethod();
+		Class<?> requiredType = queryMethod.getReturnType();
+
+		if (void.class.equals(requiredType) || requiredType.isAssignableFrom(result.getClass())) {
+			return result;
+		}
+
+		return conversionService.convert(result, requiredType);
 	}
 
 	/**

src/main/java/org/springframework/data/jpa/repository/query/JpaResultConverters.java

@@ -0,0 +1,87 @@
+/*
+ * Copyright 2014 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
+ *
+ *      http://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.jpa.repository.query;
+
+import java.io.ByteArrayOutputStream;
+import java.io.IOException;
+import java.io.InputStream;
+import java.sql.Blob;
+import java.sql.SQLException;
+
+import org.springframework.core.convert.converter.Converter;
+import org.springframework.dao.CleanupFailureDataAccessException;
+import org.springframework.dao.DataRetrievalFailureException;
+import org.springframework.util.StreamUtils;
+
+/**
+ * Container for additional JPA result {@link Converter}s.
+ * 
+ * @author Thomas Darimont
+ * @since 1.6
+ */
+class JpaResultConverters {
+
+	/**
+	 * {@code private} to prevent instantiation.
+	 */
+	private JpaResultConverters() {}
+
+	/**
+	 * Converts the given {@link Blob} into a {@code byte[]}.
+	 * 
+	 * @author Thomas Darimont
+	 */
+	enum BlobToByteArrayConverter implements Converter<Blob, byte[]> {
+
+		INSTANCE;
+
+		@Override
+		public byte[] convert(Blob source) {
+
+			if (source == null) {
+				return null;
+			}
+
+			InputStream blobStream = null;
+			try {
+
+				blobStream = source.getBinaryStream();
+
+				if (blobStream != null) {
+
+					ByteArrayOutputStream baos = new ByteArrayOutputStream();
+					StreamUtils.copy(blobStream, baos);
+					return baos.toByteArray();
+				}
+
+			} catch (SQLException e) {
+				throw new DataRetrievalFailureException("Couldn't retrieve data from blob.", e);
+			} catch (IOException e) {
+				throw new DataRetrievalFailureException("Couldn't retrieve data from blob.", e);
+			} finally {
+				if (blobStream != null) {
+					try {
+						blobStream.close();
+					} catch (IOException e) {
+						throw new CleanupFailureDataAccessException("Couldn't close binary stream for given blob.", e);
+					}
+				}
+			}
+
+			return null;
+		}
+	}
+}

src/test/java/org/springframework/data/jpa/repository/UserRepositoryTests.java

@@ -1390,6 +1390,23 @@ public class UserRepositoryTests {
 		flushTestUsers();
 
 		byte[] result = null; // repository.findBinaryDataByIdJpaQl(firstUser.getId());
+
+		assertThat(result.length, is(data.length));
+		assertThat(result, is(data));
+	}
+
+	/**
+	 * @see DATAJPA-506
+	 */
+	@Test
+	public void findBinaryDataByIdNative() throws Exception {
+
+		byte[] data = "Woho!!".getBytes("UTF-8");
+		firstUser.setBinaryData(data);
+
+		flushTestUsers();
+
+		byte[] result = repository.findBinaryDataByIdNative(firstUser.getId());
 		assertThat(result.length, is(data.length));
 		assertThat(result, is(data));
 	}

src/test/java/org/springframework/data/jpa/repository/sample/UserRepository.java

@@ -445,4 +445,10 @@ public interface UserRepository extends JpaRepository<User, Integer>, JpaSpecifi
 	 * @see DATAJPA-551
 	 */
 	Slice<User> findTop2UsersBy(Pageable page);
+	
+	/**
+	 * @see DATAJPA-506
+	 */
+	@Query(value = "select u.binaryData from User u where u.id = ?", nativeQuery = true)
+	byte[] findBinaryDataByIdNative(Integer id);
 }