Improve class mapping in SchemaMappingInspector

spring-graphql-docs/modules/ROOT/pages/request-execution.adoc

@@ -280,21 +280,26 @@ For unions, the inspection iterates over member types and tries to find the corr
 classes. For interfaces, the inspection iterates over implementation types and looks
 for the corresponding classes.
 
-By default, corresponding `Class` can be found if the class name matches that of the
-GraphQL union member of interface implementation type, _and_ the `Class` is located in
-the same package (and/or outer class) as the return type of the controller method for the
-union or interface. In addition, if `ClassNameTypeResolver` is configured as a
+By default, corresponding Java classes can be detected out-of-the-box in the following cases:
+
+- The ``Class``'s simple name matches the GraphQL union member of interface implementation
+type name, _and_ the `Class` is located in the same package as the return type of the
+controller method, or controller class, mapped to the union or interface field.
+- The `Class` is inspected in other parts of the schema where the mapped field is of a
+concrete union member or interface implementation type.
+- You have registered a
 xref:request-execution.adoc#execution.graphqlsource.default-type-resolver[TypeResolver]
-with explicit class mapping registrations, those are also checked.
+that has explicit `Class` to GraphQL type mappings .
 
-If a union member or an interface implementation type is listed as skipped, you have
-the following additional options:
+In none the above help, and GraphQL types are reported as skipped in the schema inspection
+report, you can make the following customizations:
 
-- Register a function to resolve the `Class` name for a given GraphQL type to account
-for class naming conventions.
-- Register a `ClassResolver` with any custom resolution logic.
+- Explicitly map a GraphQL type name to a Java class or classes.
+- Configure a function that customizes how a GraphQL type name is adapted to a simple
+`Class` name. This can help with a specific Java class naming conventions.
+- Provide a `ClassNameTypeResolver` to map a GraphQL type a Java classes.
 
-Use the following for such customizations:
+For example:
 
 [source,java,indent=0,subs="verbatim,quotes"]
 ----
@@ -302,10 +307,8 @@ GraphQlSource.Builder builder = ...
 
 builder.schemaResources(..)
 	.inspectSchemaMappings(
-		initializer -> initializer.classNameFunction(type -> type.getName() + "Impl")
-		report -> {
-			logger.debug(report);
-		})
+		initializer -> initializer.classMapping("Author", Author.class)
+		logger::debug);
 ----
 
 

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

@@ -238,10 +238,7 @@ final class DefaultSchemaResourceGraphQlSourceBuilder
 		// Add explicit mappings from ClassNameTypeResolver's
 		runtimeWiring.getTypeResolvers().values().stream().distinct().forEach((resolver) -> {
 			if (resolver instanceof ClassNameTypeResolver cntr) {
-				Map<Class<?>, String> mappings = cntr.getMappings();
-				if (!mappings.isEmpty()) {
-					initializer.classResolver(SchemaMappingInspector.ClassResolver.create(mappings));
-				}
+				cntr.getMappings().forEach((aClass, name) -> initializer.classMapping(name, aClass));
 			}
 		});
 

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

@@ -302,20 +302,43 @@ public final class SchemaMappingInspector {
 	public interface Initializer {
 
 		/**
-		 * Provide a function to derive the simple class name that corresponds to a
-		 * GraphQL union member type, or a GraphQL interface implementation type.
-		 * This is then used to find a Java class in the same package as that of
-		 * the return type of the controller method for the interface or union.
-		 * <p>The default, {@link GraphQLObjectType#getName()} is used
+		 * Provide an explicit mapping between a GraphQL type name and the Java
+		 * class(es) that represent it at runtime to help inspect union member
+		 * and interface implementation types when those associations cannot be
+		 * discovered otherwise.
+		 * <p>Out of the box, there a several ways through which schema inspection
+		 * can locate such types automatically:
+		 * <ul>
+		 * <li>Java class representations are located in the same package as the
+		 * type returned from the controller method for a union or interface field,
+		 * and their {@link Class#getSimpleName() simple class names} match GraphQL
+		 * type names, possibly with the help of a {@link #classNameFunction}.
+		 * <li>Java class representations are located in the same package as the
+		 * declaring class of the controller method for a union or interface field.
+		 * <li>Controller methods return the Java class representations of schema
+		 * fields for concrete union member or interface implementation types.
+		 * </ul>
+		 * @param graphQlTypeName the name of a GraphQL Object type
+		 * @param aClass one or more Java class representations
+		 * @return the same initializer instance
+		 */
+		Initializer classMapping(String graphQlTypeName, Class<?>... aClass);
+
+		/**
+		 * Help to derive the {@link Class#getSimpleName() simple class name} for
+		 * the Java representation of a GraphQL union member or interface implementing
+		 * type. For more details, see {@link #classMapping(String, Class[])}.
+		 * <p>By default, {@link GraphQLObjectType#getName()} is used.
 		 * @param function the function to use
 		 * @return the same initializer instance
 		 */
 		Initializer classNameFunction(Function<GraphQLObjectType, String> function);
 
 		/**
-		 * Add a custom {@link ClassResolver} to use to find the Java class for a
-		 * GraphQL union member type, or a GraphQL interface implementation type.
-		 * @param resolver the resolver to add
+		 * Alternative to {@link #classMapping(String, Class[])} with a custom
+		 * {@link ClassResolver} to find the Java class(es) for a GraphQL union
+		 * member or interface implementation type.
+		 * @param resolver the resolver to use to find associated Java classes
 		 * @return the same initializer instance
 		 */
 		Initializer classResolver(ClassResolver resolver);
@@ -345,14 +368,6 @@ public final class SchemaMappingInspector {
 		 */
 		List<Class<?>> resolveClass(GraphQLObjectType objectType, GraphQLNamedOutputType interfaceOrUnionType);
 
-
-		/**
-		 * Create a resolver from the given mappings.
-		 * @param mappings from Class to GraphQL type name
-		 */
-		static ClassResolver create(Map<Class<?>, String> mappings) {
-			return new MappingClassResolver(mappings);
-		}
 	}
 
 
@@ -365,6 +380,8 @@ public final class SchemaMappingInspector {
 
 		private final List<ClassResolver> classResolvers = new ArrayList<>();
 
+		private final MultiValueMap<String, Class<?>> classMappings = new LinkedMultiValueMap<>();
+
 		@Override
 		public Initializer classNameFunction(Function<GraphQLObjectType, String> function) {
 			this.classNameFunction = function;
@@ -377,14 +394,20 @@ public final class SchemaMappingInspector {
 			return this;
 		}
 
+		@Override
+		public Initializer classMapping(String graphQlTypeName, Class<?>... classes) {
+			for (Class<?> aClass : classes) {
+				this.classMappings.add(graphQlTypeName, aClass);
+			}
+			return this;
+		}
+
 		@Override
 		public SchemaReport inspect(GraphQLSchema schema, Map<String, Map<String, DataFetcher>> fetchers) {
 
-			ReflectionClassResolver reflectionResolver =
-					ReflectionClassResolver.create(schema, fetchers, this.classNameFunction);
-
 			List<ClassResolver> resolvers = new ArrayList<>(this.classResolvers);
-			resolvers.add(reflectionResolver);
+			resolvers.add(new MappingClassResolver(this.classMappings));
+			resolvers.add(ReflectionClassResolver.create(schema, fetchers, this.classNameFunction));
 
 			InterfaceUnionLookup lookup = InterfaceUnionLookup.create(schema, resolvers);
 
@@ -399,15 +422,15 @@ public final class SchemaMappingInspector {
 	 */
 	private static final class MappingClassResolver implements ClassResolver {
 
-		private final MultiValueMap<String, Class<?>> map = new LinkedMultiValueMap<>();
+		private final MultiValueMap<String, Class<?>> mappings = new LinkedMultiValueMap<>();
 
-		MappingClassResolver(Map<Class<?>, String> mappings) {
-			mappings.forEach((key, value) -> this.map.add(value, key));
+		MappingClassResolver(MultiValueMap<String, Class<?>> mappings) {
+			this.mappings.putAll(mappings);
 		}
 
 		@Override
 		public List<Class<?>> resolveClass(GraphQLObjectType objectType, GraphQLNamedOutputType interfaceOrUnionType) {
-			return this.map.getOrDefault(objectType.getName(), Collections.emptyList());
+			return this.mappings.getOrDefault(objectType.getName(), Collections.emptyList());
 		}
 	}
 
@@ -478,7 +501,7 @@ public final class SchemaMappingInspector {
 						if (PACKAGE_PREDICATE.test(clazz.getPackageName())) {
 							addClassPrefix(outputTypeName, clazz, classPrefixes);
 						}
-						else if (dataFetcher instanceof SelfDescribingDataFetcher<?> selfDescribing) {
+						if (dataFetcher instanceof SelfDescribingDataFetcher<?> selfDescribing) {
 							if (selfDescribing.getReturnType().getSource() instanceof MethodParameter param) {
 								addClassPrefix(outputTypeName, param.getDeclaringClass(), classPrefixes);
 							}

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

@@ -17,13 +17,11 @@
 package org.springframework.graphql.execution;
 
 import java.util.List;
-import java.util.Map;
 
 import org.junit.jupiter.api.Nested;
 import org.junit.jupiter.api.Test;
 
 import org.springframework.graphql.data.method.annotation.QueryMapping;
-import org.springframework.graphql.execution.SchemaMappingInspector.ClassResolver;
 import org.springframework.stereotype.Controller;
 
 /**
@@ -103,10 +101,8 @@ public class SchemaMappingInspectorInterfaceTests extends SchemaMappingInspector
 		@Test
 		void classNameTypeResolver() {
 
-			Map<Class<?>, String> mappings = Map.of(CarImpl.class, "Car");
-
 			SchemaReport report = inspectSchema(schema,
-					initializer -> initializer.classResolver(ClassResolver.create(mappings)),
+					initializer -> initializer.classMapping("Car", CarImpl.class),
 					VehicleController.class);
 
 			assertThatReport(report)

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

@@ -17,14 +17,12 @@
 package org.springframework.graphql.execution;
 
 import java.util.List;
-import java.util.Map;
 
 import org.junit.jupiter.api.Nested;
 import org.junit.jupiter.api.Test;
 
 import org.springframework.graphql.data.method.annotation.Argument;
 import org.springframework.graphql.data.method.annotation.QueryMapping;
-import org.springframework.graphql.execution.SchemaMappingInspector.ClassResolver;
 import org.springframework.stereotype.Controller;
 
 /**
@@ -129,10 +127,8 @@ public class SchemaMappingInspectorUnionTests extends SchemaMappingInspectorTest
 		@Test
 		void classNameTypeResolver() {
 
-			Map<Class<?>, String> mappings = Map.of(PhotoImpl.class, "Photo");
-
 			SchemaReport report = inspectSchema(schema,
-					initializer -> initializer.classResolver(ClassResolver.create(mappings)),
+					initializer -> initializer.classMapping("Photo", PhotoImpl.class),
 					SearchController.class);
 
 			assertThatReport(report)