Support for default TypeResolver

See gh-154

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

@@ -0,0 +1,124 @@
+/*
+ * Copyright 2002-2021 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
+ *
+ *      https://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.graphql.execution;
+
+import java.util.LinkedHashMap;
+import java.util.Map;
+import java.util.function.Function;
+
+import graphql.TypeResolutionEnvironment;
+import graphql.schema.GraphQLObjectType;
+import graphql.schema.GraphQLSchema;
+import graphql.schema.TypeResolver;
+
+import org.springframework.lang.Nullable;
+import org.springframework.util.Assert;
+
+/**
+ * {@link TypeResolver} that tries to find a GraphQL Object type based on the
+ * class name of an Object. If necessary, it walks up the base class and
+ * interface hierarchy to find a match.
+ *
+ * @author Rossen Stoyanchev
+ * @since 1.0.0
+ */
+public class ClassNameTypeResolver implements TypeResolver {
+
+	private Function<Class<?>, String> classNameExtractor = Class::getSimpleName;
+
+	private final Map<Class<?>, String> mappings = new LinkedHashMap<>();
+
+
+	/**
+	 * Customize how the name of a class, or base class/interface, is determined.
+	 * An application can use this to adapt to a common naming convention, e.g.
+	 * removing "Impl" as a suffix, or "Base" as prefix, and so on.
+	 * <p>By default, this is {@link Class#getSimpleName()}.
+	 * @param classNameExtractor the function to use
+	 */
+	public void setClassNameExtractor(Function<Class<?>, String> classNameExtractor) {
+		Assert.notNull(classNameExtractor, "'classNameExtractor' is required");
+		this.classNameExtractor = classNameExtractor;
+	}
+
+	/**
+	 * Add a mapping from a Java {@link Class} to a GraphQL Object type. The
+	 * given class can be a base class or an interface, in which case the mapping
+	 * applies to sub-classes too.
+	 * @param clazz the Java class to map
+	 * @param graphQlTypeName the matching GraphQL object type
+	 */
+	public void addMapping(Class<?> clazz, String graphQlTypeName) {
+		this.mappings.put(clazz, graphQlTypeName);
+	}
+
+
+	@Override
+	public GraphQLObjectType getType(TypeResolutionEnvironment environment) {
+		Class<?> clazz = environment.getObject().getClass();
+		GraphQLObjectType type = getTypeForClass(clazz, environment.getSchema());
+		Assert.state(type != null, "No GraphQL Object type for class: " + clazz.getName());
+		return type;
+	}
+
+	@Nullable
+	private GraphQLObjectType getTypeForClass(Class<?> clazz, GraphQLSchema schema) {
+		if (clazz.getName().startsWith("java.")) {
+			return null;
+		}
+
+		String name = getMapping(clazz);
+		if (name != null) {
+			GraphQLObjectType objectType = schema.getObjectType(name);
+			if (objectType == null) {
+				throw new IllegalStateException(
+						"Invalid mapping for " + clazz.getName() + ". " +
+								"No GraphQL Object type with name '" + name + "'.");
+			}
+			return objectType;
+		}
+
+		name = this.classNameExtractor.apply(clazz);
+		if (schema.containsType(name)) {
+			return schema.getObjectType(name);
+		}
+
+		for (Class<?> interfaceType : clazz.getInterfaces()) {
+			GraphQLObjectType objectType = getTypeForClass(interfaceType, schema);
+			if (objectType != null) {
+				return objectType;
+			}
+		}
+
+		Class<?> superclass = clazz.getSuperclass();
+		if (superclass != Object.class && superclass != null) {
+			return getTypeForClass(superclass, schema);
+		}
+
+		return null;
+	}
+
+	@Nullable
+	private String getMapping(Class<?> targetClass) {
+		for (Map.Entry<Class<?>, String> entry : this.mappings.entrySet()) {
+			if (entry.getKey().isAssignableFrom(targetClass)) {
+				return entry.getValue();
+			}
+		}
+		return null;
+	}
+
+}

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

@@ -29,10 +29,13 @@ import java.util.function.Consumer;
 import graphql.GraphQL;
 import graphql.execution.instrumentation.ChainedInstrumentation;
 import graphql.execution.instrumentation.Instrumentation;
+import graphql.language.InterfaceTypeDefinition;
+import graphql.language.UnionTypeDefinition;
 import graphql.schema.GraphQLCodeRegistry;
 import graphql.schema.GraphQLSchema;
 import graphql.schema.GraphQLTypeVisitor;
 import graphql.schema.SchemaTraverser;
+import graphql.schema.TypeResolver;
 import graphql.schema.idl.RuntimeWiring;
 import graphql.schema.idl.SchemaGenerator;
 import graphql.schema.idl.SchemaParser;
@@ -55,6 +58,9 @@ class DefaultGraphQlSourceBuilder implements GraphQlSource.Builder {
 
 	private final List<RuntimeWiringConfigurer> runtimeWiringConfigurers = new ArrayList<>();
 
+	@Nullable
+	private TypeResolver defaultTypeResolver;
+
 	private final List<DataFetcherExceptionResolver> exceptionResolvers = new ArrayList<>();
 
 	private final List<GraphQLTypeVisitor> typeVisitors = new ArrayList<>();
@@ -80,6 +86,12 @@ class DefaultGraphQlSourceBuilder implements GraphQlSource.Builder {
 		return this;
 	}
 
+	@Override
+	public GraphQlSource.Builder defaultTypeResolver(TypeResolver typeResolver) {
+		this.defaultTypeResolver = typeResolver;
+		return this;
+	}
+
 	@Override
 	public GraphQlSource.Builder exceptionResolvers(List<DataFetcherExceptionResolver> resolvers) {
 		this.exceptionResolvers.addAll(resolvers);
@@ -122,9 +134,12 @@ class DefaultGraphQlSourceBuilder implements GraphQlSource.Builder {
 		this.runtimeWiringConfigurers.forEach(configurer -> configurer.configure(runtimeWiringBuilder));
 		RuntimeWiring runtimeWiring = runtimeWiringBuilder.build();
 
+		registerDefaultTypeResolver(registry, runtimeWiring);
+
 		GraphQLSchema schema = (this.schemaFactory != null ?
 				this.schemaFactory.apply(registry, runtimeWiring) :
 				new SchemaGenerator().makeExecutableSchema(registry, runtimeWiring));
+
 		schema = applyTypeVisitors(schema);
 
 		GraphQL.Builder builder = GraphQL.newGraphQL(schema);
@@ -139,6 +154,14 @@ class DefaultGraphQlSourceBuilder implements GraphQlSource.Builder {
 		return new CachedGraphQlSource(graphQl, schema);
 	}
 
+	private void registerDefaultTypeResolver(TypeDefinitionRegistry registry, RuntimeWiring runtimeWiring) {
+		TypeResolver typeResolver =
+				(this.defaultTypeResolver != null ? this.defaultTypeResolver : new ClassNameTypeResolver());
+		registry.types().values().stream()
+				.filter(def -> def instanceof UnionTypeDefinition || def instanceof InterfaceTypeDefinition)
+				.forEach(def -> runtimeWiring.getTypeResolvers().putIfAbsent(def.getName(), typeResolver));
+	}
+
 	private TypeDefinitionRegistry parseSchemaResource(Resource schemaResource) {
 		Assert.notNull(schemaResource, "'schemaResource' not provided");
 		Assert.isTrue(schemaResource.exists(), "'schemaResource' does not exist");

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

@@ -25,6 +25,7 @@ import graphql.GraphQL;
 import graphql.execution.instrumentation.Instrumentation;
 import graphql.schema.GraphQLSchema;
 import graphql.schema.GraphQLTypeVisitor;
+import graphql.schema.TypeResolver;
 import graphql.schema.idl.RuntimeWiring;
 import graphql.schema.idl.TypeDefinitionRegistry;
 
@@ -89,6 +90,25 @@ public interface GraphQlSource {
 		 */
 		Builder configureRuntimeWiring(RuntimeWiringConfigurer configurer);
 
+		/**
+		 * Configure the default {@link TypeResolver} to use for GraphQL Interface
+		 * and Union types that don't already have such a registration after all
+		 * {@link #configureRuntimeWiring(RuntimeWiringConfigurer) RuntimeWiringConfigurer's}
+		 * have been applied.
+		 * <p>A GraphQL {@code TypeResolver} is used to determine the GraphQL Object
+		 * type of values returned from DataFetcher's of GraphQL Interface or
+		 * Union fields.
+		 * <p>By default this is set to {@link ClassNameTypeResolver}, which
+		 * tries to match the simple class name of the Object value to a GraphQL
+		 * Object type, and it also tries the same for supertypes (base classes
+		 * and interfaces). See the Javadoc of {@code ClassNameTypeResolver} for
+		 * further ways to customize matching a Java class to a GraphQL Object type.
+		 * @param typeResolver the {@code TypeResolver} to use
+		 * @return the current builder
+		 * @see ClassNameTypeResolver
+		 */
+		Builder defaultTypeResolver(TypeResolver typeResolver);
+
 		/**
 		 * Add {@link DataFetcherExceptionResolver}'s to use for resolving exceptions from
 		 * {@link graphql.schema.DataFetcher}'s.

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

@@ -0,0 +1,279 @@
+/*
+ * Copyright 2002-2021 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
+ *
+ *      https://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.graphql.execution;
+
+import java.util.Arrays;
+import java.util.List;
+import java.util.Map;
+
+import graphql.ExecutionResult;
+import org.junit.jupiter.api.Test;
+
+import org.springframework.graphql.GraphQlTestUtils;
+import org.springframework.graphql.RequestInput;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * Tests for interface and union type resolution via {@link ClassNameTypeResolver}.
+ * @author Rossen Stoyanchev
+ * @since 1.0.0
+ */
+public class ClassNameTypeResolverTests {
+
+	private static final List<Animal> animalList = Arrays.asList(new Dog(), new Penguin());
+
+	private static final List<?> animalAndPlantList = Arrays.asList(new GrayWolf(), new GiantRedwood());
+
+	private static final String schema = "" +
+			"type Query {" +
+			"    animals: [Animal!]!," +
+			"    sightings: [Sighting!]!" +
+			"}" +
+			"interface Animal {" +
+			"    name: String!" +
+			"}" +
+			"type Bird implements Animal {" +
+			"    name: String!" +
+			"    flightless: Boolean!" +
+			"}" +
+			"type Mammal implements Animal {" +
+			"    name: String!" +
+			"    herbivore: Boolean!" +
+			"}" +
+			"type Plant {" +
+			"    family: String!" +
+			"}" +
+			"type Vegetable {" +
+			"    family: String!" +
+			"}" +
+			"union Sighting = Bird | Mammal | Plant | Vegetable ";
+
+
+	@Test
+	void typeResolutionViaSuperHierarchy() {
+
+		GraphQlSource graphQlSource =
+				GraphQlTestUtils.initGraphQlSource(schema, "Query", "animals", env -> animalList).build();
+
+		String query = "" +
+				"query Animals {" +
+				"  animals {" +
+				"    __typename" +
+				"    name" +
+				"    ... on Bird {" +
+				"      flightless" +
+				"    }" +
+				"    ... on Mammal {" +
+				"      herbivore" +
+				"    }" +
+				"  }" +
+				"}";
+
+		ExecutionResult result = new ExecutionGraphQlService(graphQlSource)
+				.execute(new RequestInput(query, null, null))
+				.block();
+
+		List<Map<String, Object>> actualAnimals = GraphQlTestUtils.checkErrorsAndGetData(result, "animals");
+
+		for (int i = 0; i < animalList.size(); i++) {
+			Map<String, Object> actualAnimal = actualAnimals.get(i);
+			Animal animal = animalList.get(i);
+			assertThat(actualAnimal.get("name")).isEqualTo(animal.getName());
+
+			if (animal instanceof Bird) {
+				assertThat(actualAnimal.get("flightless")).isEqualTo(((Bird) animal).isFlightless());
+			}
+			else if (animal instanceof Mammal) {
+				assertThat(actualAnimal.get("herbivore")).isEqualTo(((Mammal) animal).isHerbivore());
+			}
+			else {
+				throw new IllegalStateException();
+			}
+		}
+	}
+
+	@Test
+	void typeResolutionViaMapping() {
+
+		ClassNameTypeResolver typeResolver = new ClassNameTypeResolver();
+		typeResolver.addMapping(Tree.class, "Plant");
+
+		GraphQlSource graphQlSource =
+				GraphQlTestUtils.initGraphQlSource(schema, "Query", "sightings", env -> animalAndPlantList)
+						.defaultTypeResolver(typeResolver)
+						.build();
+
+		String query = "" +
+				"query Sightings {" +
+				"  sightings {" +
+				"    __typename" +
+				"    ... on Bird {" +
+				"      name" +
+				"    }" +
+				"    ... on Mammal {" +
+				"      name" +
+				"    }" +
+				"    ... on Plant {" +
+				"      family" +
+				"    }" +
+				"  }" +
+				"}";
+
+		ExecutionResult result = new ExecutionGraphQlService(graphQlSource)
+				.execute(new RequestInput(query, null, null))
+				.block();
+
+		List<Map<String, Object>> actualSightings = GraphQlTestUtils.checkErrorsAndGetData(result, "sightings");
+
+		for (int i = 0; i < animalAndPlantList.size(); i++) {
+			Map<String, Object> actualSighting = actualSightings.get(i);
+			Object sighting = animalAndPlantList.get(i);
+
+			if (sighting instanceof Animal) {
+				assertThat(actualSighting.get("name")).isEqualTo(((Animal) sighting).getName());
+			}
+			else if (sighting instanceof Tree) {
+				assertThat(actualSighting.get("family")).isEqualTo(((Tree) sighting).getFamily());
+			}
+			else {
+				throw new IllegalStateException();
+			}
+		}
+	}
+
+
+	interface Animal {
+
+		String getName();
+
+	}
+
+
+	interface Bird extends Animal {
+
+		boolean isFlightless();
+
+	}
+
+
+	interface Mammal extends Animal {
+
+		boolean isHerbivore();
+
+	}
+
+
+	static class BaseAnimal implements Animal {
+
+		final String name;
+
+		BaseAnimal(String name) {
+			this.name = name;
+		}
+
+		@Override
+		public String getName() {
+			return this.name;
+		}
+
+	}
+
+
+	static class BaseBird extends BaseAnimal implements Bird {
+
+		private final boolean flightless;
+
+		BaseBird(String name, boolean flightless) {
+			super(name);
+			this.flightless = flightless;
+		}
+
+		@Override
+		public boolean isFlightless() {
+			return this.flightless;
+		}
+
+	}
+
+
+	static class BaseMammal extends BaseAnimal implements Mammal {
+
+		private final boolean isHerbivore;
+
+		BaseMammal(String name, boolean isHerbivore) {
+			super(name);
+			this.isHerbivore = isHerbivore;
+		}
+
+		@Override
+		public boolean isHerbivore() {
+			return this.isHerbivore;
+		}
+
+	}
+
+
+	static class Penguin extends BaseBird {
+
+		Penguin() {
+			super("Penguin", true);
+		}
+
+	}
+
+
+	static class Dog extends BaseMammal {
+
+		Dog() {
+			super("Dog", false);
+		}
+
+	}
+
+
+	static class GrayWolf extends BaseMammal {
+
+		GrayWolf() {
+			super("Gray Wolf", false);
+		}
+
+	}
+
+
+	static class Tree {
+
+		private final String family;
+
+		Tree(String family) {
+			this.family = family;
+		}
+
+		public String getFamily() {
+			return family;
+		}
+	}
+
+
+	static class GiantRedwood extends Tree {
+
+		GiantRedwood() {
+			super("Redwood");
+		}
+
+	}
+
+}