DATAJDBC-189 - Polishing.

Removed DefaultNamingStrategy since we don't have GA release breaking APIs is still ok.
Introduced an instance of NamingStrategy so we don't have to create a new class whereever we just want the default implementation.

JavaDoc.
Formatting

Original pull request: #36.

src/main/java/org/springframework/data/jdbc/mapping/model/DefaultNamingStrategy.java

@@ -1,30 +0,0 @@
-/*
- * Copyright 2017-2018 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.jdbc.mapping.model;
-
-/**
- * Basic implementation of {@link NamingStrategy} with no schema, table based on {@link Class} and
- * column name based on {@link JdbcPersistentProperty}.
- *
- * NOTE: Can also be used as an adapter. Create an anonymous subclass and override any settings to implement
- * a different strategy on the fly.
- *
- * @author Greg Turnquist
- * @author Michael Simons
- * @deprecated Use {@link NamingStrategy} for a default implementation and implement methods as needed
- */
-public class DefaultNamingStrategy implements NamingStrategy {
-}

src/main/java/org/springframework/data/jdbc/mapping/model/DelimiterNamingStrategy.java

@@ -22,14 +22,14 @@ import org.springframework.data.util.ParsingUtils;
  * column name based on {@link JdbcPersistentProperty}. The default delimiter is '_', resulting in snake case.
  *
  * @author Kazuki Shimizu
+ * @author Jens Schauder
  */
-public class DelimiterNamingStrategy extends DefaultNamingStrategy {
+public class DelimiterNamingStrategy implements NamingStrategy {
 
 	private final String delimiter;
 
 	/**
-	 * Construct a instance with '_' as delimiter.
-	 * This results in a snake case naming strategy.
+	 * Construct a instance with '_' as delimiter. This results in a snake case naming strategy.
 	 */
 	public DelimiterNamingStrategy() {
 		this("_");
@@ -49,7 +49,7 @@ public class DelimiterNamingStrategy extends DefaultNamingStrategy {
 	 */
 	@Override
 	public String getTableName(Class<?> type) {
-		return ParsingUtils.reconcatenateCamelCase(super.getTableName(type), delimiter);
+		return ParsingUtils.reconcatenateCamelCase(NamingStrategy.super.getTableName(type), delimiter);
 	}
 
 	/**
@@ -57,7 +57,7 @@ public class DelimiterNamingStrategy extends DefaultNamingStrategy {
 	 */
 	@Override
 	public String getColumnName(JdbcPersistentProperty property) {
-		return ParsingUtils.reconcatenateCamelCase(super.getColumnName(property), delimiter);
+		return ParsingUtils.reconcatenateCamelCase(NamingStrategy.super.getColumnName(property), delimiter);
 	}
 
 	/**

src/main/java/org/springframework/data/jdbc/mapping/model/JdbcMappingContext.java

@@ -71,7 +71,7 @@ public class JdbcMappingContext extends AbstractMappingContext<JdbcPersistentEnt
 	}
 
 	public JdbcMappingContext(NamedParameterJdbcOperations template) {
-		this(new DefaultNamingStrategy(), template, __ -> {});
+		this(NamingStrategy.INSTANCE, template, __ -> {});
 	}
 
 	@Override

src/main/java/org/springframework/data/jdbc/mapping/model/NamingStrategy.java

@@ -16,21 +16,28 @@
 package org.springframework.data.jdbc.mapping.model;
 
 /**
- * Interface and default implementation of a naming strategy. Defaults to no schema, 
- * table name based on {@link Class} and column name based on {@link JdbcPersistentProperty}.
- *
- * NOTE: Can also be used as an adapter. Create a lambda or an anonymous subclass and 
- * override any settings to implement a different strategy on the fly.
+ * Interface and default implementation of a naming strategy. Defaults to no schema, table name based on {@link Class}
+ * and column name based on {@link JdbcPersistentProperty}.
+ * <p>
+ * NOTE: Can also be used as an adapter. Create a lambda or an anonymous subclass and override any settings to implement
+ * a different strategy on the fly.
  * 
  * @author Greg Turnquist
  * @author Michael Simons
  */
 public interface NamingStrategy {
 
+	/**
+	 * Empty implementation of the interface utilizing only the default implementation.
+	 * <p>
+	 * Using this avoids creating essentially the same class over and over again.
+	 */
+	NamingStrategy INSTANCE = new NamingStrategy() {};
+
 	/**
 	 * Defaults to no schema.
 	 *
-	 * @return No schema
+	 * @return Empty String representing no schema
 	 */
 	default String getSchema() {
 		return "";
@@ -58,17 +65,19 @@ public interface NamingStrategy {
 	 * For a reference A -&gt; B this is the name in the table for B which references A.
 	 *
 	 * @param property The property who's column name in the owner table is required
-	 * @return a column name.
+	 * @return a column name. Must not be {@code null}.
 	 */
 	default String getReverseColumnName(JdbcPersistentProperty property) {
 		return property.getOwner().getTableName();
 	}
 
 	/**
-	 * For a map valued reference A -> Map&gt;X,B&lt; this is the name of the column in the tabel for B holding the key of the map.
-	 * @return
+	 * For a map valued reference A -> Map&gt;X,B&lt; this is the name of the column in the table for B holding the key of
+	 * the map.
+	 * 
+	 * @return name of the key column. Must not be {@code null}.
 	 */
-	default String getKeyColumn(JdbcPersistentProperty property){
+	default String getKeyColumn(JdbcPersistentProperty property) {
 		return getReverseColumnName(property) + "_key";
 	}
 

src/main/java/org/springframework/data/jdbc/repository/config/JdbcConfiguration.java

@@ -20,7 +20,6 @@ import java.util.Optional;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
 import org.springframework.data.jdbc.mapping.model.ConversionCustomizer;
-import org.springframework.data.jdbc.mapping.model.DefaultNamingStrategy;
 import org.springframework.data.jdbc.mapping.model.JdbcMappingContext;
 import org.springframework.data.jdbc.mapping.model.NamingStrategy;
 import org.springframework.jdbc.core.namedparam.NamedParameterJdbcTemplate;
@@ -35,9 +34,9 @@ public class JdbcConfiguration {
 
 	@Bean
 	JdbcMappingContext jdbcMappingContext(NamedParameterJdbcTemplate template, Optional<NamingStrategy> namingStrategy,
-										  Optional<ConversionCustomizer> conversionCustomizer) {
+			Optional<ConversionCustomizer> conversionCustomizer) {
 
-		return new JdbcMappingContext(
-				namingStrategy.orElse(new DefaultNamingStrategy()), template, conversionCustomizer.orElse(conversionService -> {}));
+		return new JdbcMappingContext(namingStrategy.orElse(NamingStrategy.INSTANCE), template,
+				conversionCustomizer.orElse(conversionService -> {}));
 	}
 }