DATAJDBC-296 - The value of the @Table annotation is now optional.

The default ("") is equivalent to no annotation at all, i.e. the `NamingStrategy` determines the table name.

Original pull request: #109.

src/main/java/org/springframework/data/relational/core/mapping/RelationalPersistentEntityImpl.java

@@ -21,12 +21,14 @@ import org.springframework.data.mapping.model.BasicPersistentEntity;
 import org.springframework.data.mapping.model.PersistentPropertyAccessorFactory;
 import org.springframework.data.util.Lazy;
 import org.springframework.data.util.TypeInformation;
+import org.springframework.util.StringUtils;
 
 /**
  * Meta data a repository might need for implementing persistence operations for instances of type {@code T}
  *
  * @author Jens Schauder
  * @author Greg Turnquist
+ * @author Bastian Wilhelm
  */
 class RelationalPersistentEntityImpl<T> extends BasicPersistentEntity<T, RelationalPersistentProperty>
 		implements RelationalPersistentEntity<T> {
@@ -44,7 +46,11 @@ class RelationalPersistentEntityImpl<T> extends BasicPersistentEntity<T, Relatio
 		super(information);
 
 		this.namingStrategy = namingStrategy;
-		this.tableName = Lazy.of(() -> Optional.ofNullable(findAnnotation(Table.class)).map(Table::value));
+		this.tableName = Lazy.of(() -> Optional.ofNullable( //
+				findAnnotation(Table.class)) //
+				.map(Table::value) //
+				.filter(StringUtils::hasText) //
+		);
 	}
 
 	/* 

src/main/java/org/springframework/data/relational/core/mapping/Table.java

@@ -26,6 +26,7 @@ import java.lang.annotation.Target;
  * The annotation to configure the mapping from a class to a database table.
  *
  * @author Kazuki Shimizu
+ * @author Bastian Wilhelm
  */
 @Retention(RetentionPolicy.RUNTIME)
 @Target(ElementType.TYPE)
@@ -36,5 +37,5 @@ public @interface Table {
 	/**
 	 * The mapping table name.
 	 */
-	String value();
+	String value() default "";
 }

src/test/java/org/springframework/data/relational/core/mapping/RelationalPersistentEntityWithoutNamesImplUnitTests.java

@@ -0,0 +1,52 @@
+/*
+ * Copyright 2018-2019 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.relational.core.mapping;
+
+import org.junit.Test;
+import org.springframework.data.annotation.Id;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * Unit tests for {@link RelationalPersistentEntityImpl} without names in {@link Column} and {@link Table}.
+ * 
+ * @author Bastian Wilhelm
+ */
+public class RelationalPersistentEntityWithoutNamesImplUnitTests {
+
+	RelationalMappingContext mappingContext = new RelationalMappingContext();
+
+	@Test // DATAJDBC-296
+	public void discoversAnnotatedTableName() {
+
+		RelationalPersistentEntity<?> entity = mappingContext.getPersistentEntity(DummySubEntity.class);
+
+		assertThat(entity.getTableName()).isEqualTo("dummy_sub_entity");
+	}
+
+	@Test // DATAJDBC-296
+	public void considerIdColumnName() {
+
+		RelationalPersistentEntity<?> entity = mappingContext.getPersistentEntity(DummySubEntity.class);
+
+		assertThat(entity.getIdColumn()).isEqualTo("id");
+	}
+
+	@Table()
+	static class DummySubEntity {
+		@Id @Column() Long id;
+	}
+}