Replace argument type with @Source to determine source/parent

Closes spring-projectsgh-296

spring-graphql-docs/src/docs/asciidoc/index.adoc

@@ -1009,7 +1009,7 @@ parent type name, and the field name:
 	public class BookController {
 
 		@SchemaMapping(typeName="Book", field="author")
-		public Author getAuthor(Book book) {
+		public Author getAuthor(@Source Book book) {
 			// ...
 		}
 	}
@@ -1026,7 +1026,7 @@ defaults to type "Book" and field "author":
 	public class BookController {
 
 		@SchemaMapping
-		public Author author(Book book) {
+		public Author author(@Source Book book) {
 			// ...
 		}
 	}
@@ -1098,7 +1098,7 @@ See <<controllers-schema-mapping-arguments>>.
 | For access to field arguments through a project interface.
 See <<controllers-schema-mapping-projectedpayload-argument>>.
 
-| Source
+| @Source
 | For access to the source (i.e. parent/container) instance of the field.
 See <<controllers-schema-mapping-source>>.
 
@@ -1287,19 +1287,19 @@ For example:
 
 
 [[controllers-schema-mapping-source]]
-==== Source
+==== @Source
 
 In GraphQL Java, the `DataFetchingEnvironment` provides access to the source (i.e.
 parent/container) instance of the field. To access this, simply declare a method parameter
-of the expected target type.
+annotated with `@Source`.
 
 [source,java,indent=0,subs="verbatim,quotes"]
 ----
 	@Controller
 	public class BookController {
 
 		@SchemaMapping
-		public Author author(Book book) {
+		public Author author(@Source Book book) {
 			// ...
 		}
 	}

spring-graphql/src/main/java/org/springframework/graphql/data/method/annotation/Source.java

@@ -0,0 +1,38 @@
+/*
+ * Copyright 2002-2022 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.data.method.annotation;
+
+import graphql.schema.DataFetchingEnvironment;
+
+import java.lang.annotation.Documented;
+import java.lang.annotation.ElementType;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
+
+/**
+ * Annotation to bind a method parameter to the
+ * {@link DataFetchingEnvironment#getSource() source/parent} instance of the field.
+ *
+ * @author Genkui Du
+ * @since 1.0.0
+ */
+@Target(ElementType.PARAMETER)
+@Retention(RetentionPolicy.RUNTIME)
+@Documented
+public @interface Source {
+
+}

spring-graphql/src/main/java/org/springframework/graphql/data/method/annotation/support/SourceMethodArgumentResolver.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2021 the original author or authors.
+ * Copyright 2002-2022 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.
@@ -15,32 +15,26 @@
  */
 package org.springframework.graphql.data.method.annotation.support;
 
-import java.util.Collection;
-
 import graphql.schema.DataFetchingEnvironment;
 
-import org.springframework.beans.BeanUtils;
 import org.springframework.core.MethodParameter;
 import org.springframework.graphql.data.method.HandlerMethodArgumentResolver;
+import org.springframework.graphql.data.method.annotation.Source;
 import org.springframework.util.Assert;
 
 /**
  * Resolver for the source/parent of a field, obtained via
  * {@link DataFetchingEnvironment#getSource()}.
  *
- * <p>This resolver supports any non-simple value type, also excluding arrays
- * and collections, and therefore must be ordered last, in a fallback mode,
- * allowing other resolvers to resolve the argument first.
- *
  * @author Rossen Stoyanchev
+ * @author Genkui Du
  * @since 1.0.0
  */
 public class SourceMethodArgumentResolver implements HandlerMethodArgumentResolver {
 
 	@Override
 	public boolean supportsParameter(MethodParameter parameter) {
-		Class<?> type = parameter.getParameterType();
-		return (!BeanUtils.isSimpleValueType(type) && !type.isArray() && !Collection.class.isAssignableFrom(type));
+		return parameter.getParameterAnnotation(Source.class) != null;
 	}
 
 	@Override
@@ -49,7 +43,7 @@ public Object resolveArgument(MethodParameter parameter, DataFetchingEnvironment
 		Assert.isInstanceOf(parameter.getParameterType(), source,
 				"The declared parameter of type '" + parameter.getParameterType() + "' " +
 						"does not match the type of the source Object '" + source.getClass() + "'.");
-		return source;
+		return environment.getSource();
 	}
 
 }

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

@@ -21,6 +21,7 @@
 import graphql.schema.DataFetchingEnvironment;
 import graphql.schema.idl.RuntimeWiring;
 import org.junit.jupiter.api.Test;
+import org.springframework.graphql.data.method.annotation.Source;
 import reactor.core.publisher.Flux;
 
 import org.springframework.context.annotation.AnnotationConfigApplicationContext;
@@ -118,7 +119,7 @@ public Book bookById(@Argument String id) {
 		}
 
 		@MutationMapping
-		public void saveBook(Book book) {
+		public void saveBook(@Source Book book) {
 		}
 
 		@SubscriptionMapping
@@ -127,7 +128,7 @@ public Flux<Book> bookSearch(@Argument String author) {
 		}
 
 		@SchemaMapping
-		public Author author(DataFetchingEnvironment environment, Book book) {
+		public Author author(DataFetchingEnvironment environment, @Source Book book) {
 			return null;
 		}
 
@@ -139,7 +140,7 @@ public Book bookByIdWithNonMatchingMethodName(@Argument String id) {
 		}
 
 		@MutationMapping("saveBookCustomized")
-		public void saveBookWithNonMatchingMethodName(Book book) {
+		public void saveBookWithNonMatchingMethodName(@Source Book book) {
 		}
 
 		@SubscriptionMapping("bookSearchCustomized")
@@ -148,7 +149,7 @@ public Flux<Book> bookSearchWithNonMatchingMethodName(@Argument String author) {
 		}
 
 		@SchemaMapping("authorCustomized")
-		public Author authorWithNonMatchingMethodName(Book book) {
+		public Author authorWithNonMatchingMethodName(@Source Book book) {
 			return null;
 		}
 	}

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

@@ -23,6 +23,7 @@
 import graphql.schema.DataFetchingEnvironment;
 import org.dataloader.DataLoader;
 import org.junit.jupiter.api.Test;
+import org.springframework.graphql.data.method.annotation.Source;
 import reactor.core.publisher.Flux;
 import reactor.core.publisher.Mono;
 import reactor.test.StepVerifier;
@@ -251,7 +252,7 @@ public List<Book> booksByProjectedCriteria(@Argument BookProjection criteria) {
 		}
 
 		@SchemaMapping
-		public CompletableFuture<Author> author(Book book, DataLoader<Long, Author> dataLoader) {
+		public CompletableFuture<Author> author(@Source Book book, DataLoader<Long, Author> dataLoader) {
 			return dataLoader.load(book.getAuthorId());
 		}