Support custom controller method argument resolvers

Closes gh-603

Author: rstoyanchev

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

@@ -18,6 +18,7 @@
 import java.lang.annotation.Annotation;
 import java.lang.reflect.Method;
 import java.lang.reflect.Type;
+import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collection;
 import java.util.Collections;
@@ -121,6 +122,8 @@ public class AnnotatedControllerConfigurer
 
 	private final FormattingConversionService conversionService = new DefaultFormattingConversionService();
 
+	private final List<HandlerMethodArgumentResolver> customArgumentResolvers = new ArrayList<>(8);
+
 	@Nullable
 	private HandlerMethodArgumentResolverComposite argumentResolvers;
 
@@ -147,6 +150,18 @@ public void addFormatterRegistrar(FormatterRegistrar registrar) {
 		registrar.registerFormatters(this.conversionService);
 	}
 
+	/**
+	 * Add {@link HandlerMethodArgumentResolver}'s for custom controller method
+	 * arguments. Such custom resolvers are ordered after built-in resolvers
+	 * except for {@link SourceMethodArgumentResolver}, which is always last.
+	 *
+	 * @param resolvers the resolvers to add.
+	 * @since 1.2
+	 */
+	public void setCustomArgumentResolver(List<HandlerMethodArgumentResolver> resolvers) {
+		this.customArgumentResolvers.addAll(resolvers);
+	}
+
 	HandlerMethodArgumentResolverComposite getArgumentResolvers() {
 		Assert.notNull(this.argumentResolvers,
 				"HandlerMethodArgumentResolverComposite is not yet initialized, was afterPropertiesSet called?");
@@ -243,6 +258,8 @@ private HandlerMethodArgumentResolverComposite initArgumentResolvers() {
 			resolvers.addResolver(new ContinuationHandlerMethodArgumentResolver());
 		}
 
+		this.customArgumentResolvers.forEach(resolvers::addResolver);
+
 		// This works as a fallback, after all other resolvers
 		resolvers.addResolver(new SourceMethodArgumentResolver());
 

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

@@ -0,0 +1,56 @@
+/*
+ * Copyright 2002-2023 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.support;
+
+import java.util.Collections;
+import java.util.List;
+
+import org.junit.jupiter.api.Test;
+
+import org.springframework.context.support.StaticApplicationContext;
+import org.springframework.graphql.data.method.HandlerMethodArgumentResolver;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.mockito.Mockito.mock;
+
+/**
+ * Unit tests for {@link AnnotatedControllerConfigurer}.
+ *
+ * @author Rossen Stoyanchev
+ * @since 1.2
+ */
+public class AnnotatedControllerConfigurerTests {
+
+
+	@Test
+	void customArgumentResolvers() {
+		HandlerMethodArgumentResolver customResolver1 = mock(HandlerMethodArgumentResolver.class);
+		HandlerMethodArgumentResolver customResolver2 = mock(HandlerMethodArgumentResolver.class);
+
+		AnnotatedControllerConfigurer configurer = new AnnotatedControllerConfigurer();
+		configurer.setCustomArgumentResolver(Collections.singletonList(customResolver1));
+		configurer.setCustomArgumentResolver(Collections.singletonList(customResolver2));
+		configurer.setApplicationContext(new StaticApplicationContext());
+		configurer.afterPropertiesSet();
+
+		List<HandlerMethodArgumentResolver> resolvers = configurer.getArgumentResolvers().getResolvers();
+		int size = resolvers.size();
+		assertThat(resolvers).element(size -1).isInstanceOf(SourceMethodArgumentResolver.class);
+		assertThat(resolvers).element(size -2).isSameAs(customResolver2);
+		assertThat(resolvers).element(size -3).isSameAs(customResolver1);
+	}
+
+}