#16 - Add abstract configuration class for R2DBC.

We now provide an abstract R2DBC configuration that registers beans required for R2DBC's DatabaseClient.

Original pull request: #17.

src/main/java/org/springframework/data/r2dbc/repository/config/AbstractR2dbcConfiguration.java

@@ -0,0 +1,84 @@
+package org.springframework.data.r2dbc.repository.config;
+
+import io.r2dbc.spi.ConnectionFactory;
+
+import java.util.Optional;
+
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.data.r2dbc.function.DatabaseClient;
+import org.springframework.data.r2dbc.function.DefaultReactiveDataAccessStrategy;
+import org.springframework.data.r2dbc.function.ReactiveDataAccessStrategy;
+import org.springframework.data.r2dbc.support.R2dbcExceptionTranslator;
+import org.springframework.data.r2dbc.support.SqlErrorCodeR2dbcExceptionTranslator;
+import org.springframework.data.relational.core.conversion.BasicRelationalConverter;
+import org.springframework.data.relational.core.mapping.NamingStrategy;
+import org.springframework.data.relational.core.mapping.RelationalMappingContext;
+
+/**
+ * Base class for Spring Data R2DBC configuration containing bean declarations that must be registered for Spring Data
+ * R2DBC to work.
+ *
+ * @author Mark Paluch
+ * @see ConnectionFactory
+ * @see DatabaseClient
+ * @see EnableR2dbcRepositories
+ */
+@Configuration
+public abstract class AbstractR2dbcConfiguration {
+
+	/**
+	 * Return a R2DBC {@link ConnectionFactory}. Annotate with {@link Bean} in case you want to expose a
+	 * {@link ConnectionFactory} instance to the {@link org.springframework.context.ApplicationContext}.
+	 *
+	 * @return the configured {@link ConnectionFactory}.
+	 */
+	public abstract ConnectionFactory connectionFactory();
+
+	/**
+	 * Register a {@link DatabaseClient} using {@link #connectionFactory()} and {@link RelationalMappingContext}.
+	 *
+	 * @return must not be {@literal null}.
+	 */
+	@Bean
+	public DatabaseClient databaseClient(ReactiveDataAccessStrategy dataAccessStrategy,
+			R2dbcExceptionTranslator exceptionTranslator) {
+
+		return DatabaseClient.builder().connectionFactory(connectionFactory()).dataAccessStrategy(dataAccessStrategy)
+				.exceptionTranslator(exceptionTranslator).build();
+	}
+
+	/**
+	 * Register a {@link RelationalMappingContext} and apply an optional {@link NamingStrategy}.
+	 *
+	 * @param namingStrategy optional {@link NamingStrategy}. Use {@link NamingStrategy#INSTANCE} as fallback.
+	 * @return must not be {@literal null}.
+	 */
+	@Bean
+	public RelationalMappingContext r2dbcMappingContext(Optional<NamingStrategy> namingStrategy) {
+		return new RelationalMappingContext(namingStrategy.orElse(NamingStrategy.INSTANCE));
+	}
+
+	/**
+	 * Creates a {@link ReactiveDataAccessStrategy} using the configured {@link #r2dbcMappingContext(Optional)}.
+	 *
+	 * @param mappingContext the configured {@link RelationalMappingContext}.
+	 * @return must not be {@literal null}.
+	 * @see #r2dbcMappingContext(Optional)
+	 */
+	@Bean
+	public ReactiveDataAccessStrategy reactiveDataAccessStrategy(RelationalMappingContext mappingContext) {
+		return new DefaultReactiveDataAccessStrategy(new BasicRelationalConverter(mappingContext));
+	}
+
+	/**
+	 * Creates a {@link R2dbcExceptionTranslator} using the configured {@link #connectionFactory()}.
+	 *
+	 * @return must not be {@literal null}.
+	 * @see #connectionFactory()
+	 */
+	@Bean
+	public R2dbcExceptionTranslator exceptionTranslator() {
+		return new SqlErrorCodeR2dbcExceptionTranslator(connectionFactory());
+	}
+}