Register batch load function by name

This is an alternative to providing the key and value types, which are
only used to form the DataLoader name.

See gh-130

Author: rstoyanchev

spring-graphql/src/main/java/org/springframework/graphql/execution/BatchLoaderRegistry.java

@@ -44,16 +44,39 @@
 public interface BatchLoaderRegistry {
 
 	/**
-	 * Start the registration of a new function for batch loading data values by
-	 * specifying the key and value types.
-	 * @param keyType the type of the key that identifies the value
-	 * @param valueType the type of the data value
+	 * Begin the registration of a new batch load function by specifying the
+	 * types of the keys and values that will be used as input and output.
+	 *
+	 * <p>When this method is used, the name for the
+	 * {@link org.dataloader.DataLoader} is automatically set as defined in
+	 * {@link RegistrationSpec#withName(String)}, and likewise,
+	 * {@code @SchemaMapping} handler methods can transparenly locate and
+	 * inject a {@code DataLoader<T>} argument based on the generic type
+	 * {@code <T>}.
+	 *
+	 * @param keyType the type of keys that will be used as input
+	 * @param valueType the type of value that will be returned as output
 	 * @param <K> the key type
 	 * @param <V> the value type
 	 * @return a spec to complete the registration
 	 */
 	<K, V> RegistrationSpec<K, V> forTypePair(Class<K> keyType, Class<V> valueType);
 
+	/**
+	 * Begin the registration of a new batch load function by specifying the
+	 * name for the {@link org.dataloader.DataLoader}.
+	 *
+	 * <p><strong>Note:</strong> when this method is used, the parameter name
+	 * of a {@code DataLoader<T>} argument in a {@code @SchemaMapping} handler
+	 * method needs to match the name given here.
+	 *
+	 * @param name the name to use to register a {@code DataLoader}
+	 * @param <K> the type of keys that will be used as input
+	 * @param <V> the type of values that will be used as output
+	 * @return a spec to complete the registration
+	 */
+	<K, V> RegistrationSpec<K, V> forName(String name);
+
 
 	/**
 	 * Spec to complete the registration of a batch loading function.
@@ -66,7 +89,8 @@ interface RegistrationSpec<K, V> {
 		/**
 		 * Customize the name under which the {@link org.dataloader.DataLoader}
 		 * is registered and can be accessed in the data layer.
-		 * <p>By default, this is the full class name of the value type.
+		 * <p>By default, this is the full class name of the value type, if the
+		 * value type is specified via {@link #forTypePair(Class, Class)}.
 		 * @param name the name to use
 		 * @return a spec to complete the registration
 		 */

spring-graphql/src/main/java/org/springframework/graphql/execution/DefaultBatchLoaderRegistry.java

@@ -33,6 +33,10 @@
 import reactor.core.publisher.Flux;
 import reactor.core.publisher.Mono;
 
+import org.springframework.lang.Nullable;
+import org.springframework.util.Assert;
+import org.springframework.util.StringUtils;
+
 /**
  * A default implementation of {@link BatchLoaderRegistry} that accepts
  * registrations, and also an implementation of {@link DataLoaderRegistrar} to
@@ -50,7 +54,12 @@ public class DefaultBatchLoaderRegistry implements BatchLoaderRegistry, DataLoad
 
 	@Override
 	public <K, V> RegistrationSpec<K, V> forTypePair(Class<K> keyType, Class<V> valueType) {
-		return new DefaultRegistrationSpec<>(valueType.getName());
+		return new DefaultRegistrationSpec<>(valueType);
+	}
+
+	@Override
+	public <K, V> RegistrationSpec<K, V> forName(String name) {
+		return new DefaultRegistrationSpec<>(name);
 	}
 
 	@Override
@@ -75,12 +84,21 @@ private void registerDataLoader(String name, DataLoader<?, ?> dataLoader, DataLo
 
 	private class DefaultRegistrationSpec<K, V> implements RegistrationSpec<K, V> {
 
+		@Nullable
+		private final Class<?> valueType;
+
+		@Nullable
 		private String name;
 
 		private DataLoaderOptions options = DataLoaderOptions.newOptions();
 
+		public DefaultRegistrationSpec(Class<V> valueType) {
+			this.valueType = valueType;
+		}
+
 		public DefaultRegistrationSpec(String name) {
 			this.name = name;
+			this.valueType = null;
 		}
 
 		@Override
@@ -104,13 +122,21 @@ public RegistrationSpec<K, V> withOptions(DataLoaderOptions options) {
 		@Override
 		public void registerBatchLoader(BiFunction<List<K>, BatchLoaderEnvironment, Flux<V>> loader) {
 			DefaultBatchLoaderRegistry.this.loaders.add(
-					new ReactorBatchLoader<>(this.name, loader, this.options));
+					new ReactorBatchLoader<>(initName(), loader, this.options));
 		}
 
 		@Override
 		public void registerMappedBatchLoader(BiFunction<Set<K>, BatchLoaderEnvironment, Mono<Map<K, V>>> loader) {
 			DefaultBatchLoaderRegistry.this.mappedLoaders.add(
-					new ReactorMappedBatchLoader<>(this.name, loader, this.options));
+					new ReactorMappedBatchLoader<>(initName(), loader, this.options));
+		}
+
+		private String initName() {
+			if (StringUtils.hasText(this.name)) {
+				return this.name;
+			}
+			Assert.notNull(this.valueType, "Value type not available to select a default DataLoader name.");
+			return (StringUtils.hasText(this.name) ? this.name : this.valueType.getName());
 		}
 	}
 

spring-graphql/src/test/java/org/springframework/graphql/data/method/annotation/support/DataLoaderArgumentResolverTests.java

@@ -28,7 +28,6 @@
 import org.springframework.core.DefaultParameterNameDiscoverer;
 import org.springframework.core.MethodParameter;
 import org.springframework.graphql.Author;
-import org.springframework.graphql.Book;
 import org.springframework.graphql.execution.BatchLoaderRegistry;
 import org.springframework.graphql.execution.DefaultBatchLoaderRegistry;
 import org.springframework.util.ClassUtils;
@@ -57,6 +56,7 @@ void supportsParameter() {
 
 	@Test
 	void resolveArgument() {
+
 		DataFetchingEnvironment environment = initEnvironment(registry ->
 				registry.forTypePair(Long.class, Author.class).registerBatchLoader((ids, env) -> Flux.empty()));
 
@@ -67,9 +67,7 @@ void resolveArgument() {
 	@Test
 	void resolveArgumentViaParameterName() {
 		DataFetchingEnvironment environment = initEnvironment(registry ->
-				registry.forTypePair(Long.class, Author.class)
-						.withName("namedDataLoader")
-						.registerBatchLoader((ids, env) -> Flux.empty()));
+				registry.forName("namedDataLoader").registerBatchLoader((ids, env) -> Flux.empty()));
 
 		MethodParameter parameter = initParameter(1);
 		parameter.initParameterNameDiscovery(new DefaultParameterNameDiscoverer());
@@ -90,9 +88,7 @@ void resolveArgumentFailureWithoutGenericType() {
 	@Test
 	void resolveArgumentFailureWithoutParameterName() {
 		DataFetchingEnvironment environment = initEnvironment(registry ->
-				registry.forTypePair(Long.class, Author.class)
-						.withName("namedDataLoader")
-						.registerBatchLoader((ids, env) -> Flux.empty()));
+				registry.forName("namedDataLoader").registerBatchLoader((ids, env) -> Flux.empty()));
 
 		MethodParameter parameter = initParameter(1);
 		// Skip ParameterNameDiscovery
@@ -104,9 +100,7 @@ void resolveArgumentFailureWithoutParameterName() {
 	@Test
 	void resolveArgumentFailureNoMatch() {
 		DataFetchingEnvironment environment = initEnvironment(registry ->
-				registry.forTypePair(Long.class, Book.class)
-						.withName("bookDataLoader")
-						.registerBatchLoader((ids, env) -> Flux.empty()));
+				registry.forName("bookDataLoader").registerBatchLoader((ids, env) -> Flux.empty()));
 
 		MethodParameter parameter = initParameter(0);
 		parameter.initParameterNameDiscovery(new DefaultParameterNameDiscoverer());

spring-graphql/src/test/java/org/springframework/graphql/execution/DefaultBatchLoaderRegistryTests.java

@@ -65,9 +65,7 @@ void batchLoaderWithCustomNameAndOptions() {
 		String name = "myLoader";
 		StatisticsCollector collector = new NoOpStatisticsCollector();
 
-		this.batchLoaderRegistry
-				.forTypePair(String.class, Book.class)
-				.withName(name)
+		this.batchLoaderRegistry.forName(name)
 				.withOptions(options -> options.setStatisticsCollector(() -> collector))
 				.registerBatchLoader((keys, environment) -> Flux.empty());