Order ControllerAdvice beans in controller support

Prior to this commit, the `AnnotatedControllerExceptionResolver` would
scan the application context for `@ControllerAdvice` beans and cache the
results in an unordered Map. It's later iterating over the entries to
resolve an exception handler at runtime.

This commit ensures that such entries are now stored in an ordered map,
using the `OrderComparator.INSTANCE` comparator. `ControllerAdvice`
beans will be iterated over the order specified by the `Ordered`
contract or the `@Order` annotation.

Fixes gh-830

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

@@ -23,6 +23,7 @@ import java.util.Collections;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
+import java.util.TreeMap;
 import java.util.concurrent.ConcurrentHashMap;
 
 import graphql.GraphQLError;
@@ -36,6 +37,7 @@ import org.springframework.core.ExceptionDepthComparator;
 import org.springframework.core.KotlinDetector;
 import org.springframework.core.MethodIntrospector;
 import org.springframework.core.MethodParameter;
+import org.springframework.core.OrderComparator;
 import org.springframework.core.annotation.AnnotatedElementUtils;
 import org.springframework.graphql.data.method.HandlerMethod;
 import org.springframework.graphql.data.method.HandlerMethodArgumentResolverComposite;
@@ -80,7 +82,7 @@ final class AnnotatedControllerExceptionResolver {
 
 	private final Map<Class<?>, MethodResolver> controllerCache = new ConcurrentHashMap<>(64);
 
-	private final Map<ControllerAdviceBean, MethodResolver> controllerAdviceCache = new ConcurrentHashMap<>(64);
+	private final Map<ControllerAdviceBean, MethodResolver> controllerAdviceCache = new TreeMap<>(OrderComparator.INSTANCE);
 
 
 	AnnotatedControllerExceptionResolver(HandlerMethodArgumentResolverComposite resolvers) {

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

@@ -31,6 +31,8 @@ import org.springframework.aop.target.SingletonTargetSource;
 import org.springframework.context.ApplicationContext;
 import org.springframework.context.annotation.AnnotationConfigApplicationContext;
 import org.springframework.context.support.StaticApplicationContext;
+import org.springframework.core.Ordered;
+import org.springframework.core.annotation.Order;
 import org.springframework.graphql.data.method.HandlerMethodArgumentResolverComposite;
 import org.springframework.graphql.data.method.annotation.GraphQlExceptionHandler;
 import org.springframework.lang.Nullable;
@@ -121,6 +123,20 @@ public class AnnotatedControllerExceptionResolverTests {
 		assertThat(actual.get(0).getMessage()).isEqualTo("handle: Bad input");
 	}
 
+	@Test
+	void resolveWithOrderedControllerAdvice() {
+		AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext();
+		context.register(TestControllerAdvice.class);
+		context.register(OrderedTestControllerAdvice.class);
+		context.refresh();
+
+		Exception ex = new IllegalArgumentException("Bad input");
+		List<GraphQLError> actual = exceptionResolver(context).resolveException(ex, this.environment, null).block();
+
+		assertThat(actual).hasSize(1);
+		assertThat(actual.get(0).getMessage()).isEqualTo("ordered handle: Bad input");
+	}
+
 	@Test
 	void invalidReturnType() {
 		assertThatIllegalStateException().isThrownBy(() ->
@@ -235,6 +251,19 @@ public class AnnotatedControllerExceptionResolverTests {
 	}
 
 
+	@SuppressWarnings("unused")
+	@ControllerAdvice
+	@Order(Ordered.HIGHEST_PRECEDENCE)
+	private static class OrderedTestControllerAdvice {
+
+		@GraphQlExceptionHandler
+		GraphQLError handle(IllegalArgumentException ex) {
+			return GraphQLError.newError().message("ordered handle: " + ex.getMessage()).build();
+		}
+
+	}
+
+
 	private static class InvalidReturnTypeController {
 
 		@GraphQlExceptionHandler