Apply validation only when annotations detected

Closes gh-445

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

@@ -71,7 +71,7 @@ public class DataFetcherHandlerMethod extends InvocableHandlerMethodSupport {
 		super(handlerMethod, executor);
 		Assert.isTrue(!resolvers.getResolvers().isEmpty(), "No argument resolvers");
 		this.resolvers = resolvers;
-		this.validator = validator;
+		this.validator = (validator != null && validator.requiresValidation(handlerMethod) ? validator : null);
 		this.subscription = subscription;
 	}
 

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

@@ -19,12 +19,17 @@ package org.springframework.graphql.data.method.annotation.support;
 import java.lang.annotation.Annotation;
 import java.util.Set;
 
+import javax.validation.Constraint;
 import javax.validation.ConstraintViolation;
 import javax.validation.ConstraintViolationException;
+import javax.validation.Valid;
 import javax.validation.Validator;
+import javax.validation.metadata.BeanDescriptor;
 
 import org.springframework.context.ApplicationContext;
+import org.springframework.core.MethodParameter;
 import org.springframework.core.annotation.AnnotationUtils;
+import org.springframework.core.annotation.MergedAnnotations;
 import org.springframework.graphql.data.method.HandlerMethod;
 import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
@@ -97,6 +102,34 @@ final class HandlerMethodValidationHelper {
 		return annotation;
 	}
 
+	/**
+	 * Whether the given method requires standard bean validation. This is the
+	 * case if the method or one of its parameters are annotated with
+	 * {@link Valid} or {@link Validated}, or if any method parameter is declared
+	 * with a {@link Constraint constraint}, or the method parameter type is
+	 * itself {@link BeanDescriptor#isBeanConstrained() constrained}.
+	 * @param method the handler method to check
+	 * @return {@code true} if validation is required, {@code false} otherwise
+	 */
+	public boolean requiresValidation(HandlerMethod method) {
+		if (findAnnotation(method, Validated.class) != null || findAnnotation(method, Valid.class) != null) {
+			return true;
+		}
+		for (MethodParameter parameter : method.getMethodParameters()) {
+			for (Annotation annotation : parameter.getParameterAnnotations()) {
+				MergedAnnotations merged = MergedAnnotations.from(annotation);
+				if (merged.isPresent(Valid.class) || merged.isPresent(Constraint.class) || merged.isPresent(Validated.class)) {
+					return true;
+				}
+			}
+			Class<?> paramType = parameter.nestedIfOptional().getNestedParameterType();
+			if (this.validator.getConstraintsForClass(paramType).isBeanConstrained()) {
+				return true;
+			}
+		}
+		return false;
+	}
+
 
 	/**
 	 * Factory method for {@link HandlerMethodValidationHelper} if a

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

@@ -20,9 +20,11 @@ import java.lang.annotation.Retention;
 import java.lang.annotation.RetentionPolicy;
 import java.lang.reflect.Method;
 import java.util.Arrays;
+import java.util.Optional;
 
 import javax.validation.ConstraintViolation;
 import javax.validation.ConstraintViolationException;
+import javax.validation.Valid;
 import javax.validation.Validation;
 import javax.validation.constraints.Max;
 import javax.validation.constraints.NotNull;
@@ -36,6 +38,7 @@ import org.springframework.beans.BeanUtils;
 import org.springframework.graphql.data.method.HandlerMethod;
 import org.springframework.validation.annotation.Validated;
 
+import static org.assertj.core.api.Assertions.assertThat;
 import static org.assertj.core.api.Assertions.assertThatNoException;
 import static org.assertj.core.api.Assertions.assertThatThrownBy;
 
@@ -80,6 +83,27 @@ class HandlerMethodValidationHelperTests {
 				.anyMatch(violation -> violation.getPropertyPath().toString().equals("myValidMethodWithGroupOnType.arg0"));
 	}
 
+	@Test
+	void shouldRecognizeMethodsThatRequireValidation() {
+		HandlerMethod method = findHandlerMethod(RequiresValidationBean.class, "processConstrainedValue");
+		assertThat(validator.requiresValidation(method)).isTrue();
+
+		method = findHandlerMethod(RequiresValidationBean.class, "processValidInput");
+		assertThat(validator.requiresValidation(method)).isTrue();
+
+		method = findHandlerMethod(RequiresValidationBean.class, "processValidatedInput");
+		assertThat(validator.requiresValidation(method)).isTrue();
+
+		method = findHandlerMethod(RequiresValidationBean.class, "processInputWithConstrainedValue");
+		assertThat(validator.requiresValidation(method)).isTrue();
+
+		method = findHandlerMethod(RequiresValidationBean.class, "processOptionalInputWithConstrainedValue");
+		assertThat(validator.requiresValidation(method)).isTrue();
+
+		method = findHandlerMethod(RequiresValidationBean.class, "processValue");
+		assertThat(validator.requiresValidation(method)).isFalse();
+	}
+
 
 	private HandlerMethod findHandlerMethod(Class<?> handlerType, String methodName) {
 		Object handler = BeanUtils.instantiateClass(handlerType);
@@ -147,4 +171,47 @@ class HandlerMethodValidationHelperTests {
 
 	}
 
+
+	@SuppressWarnings("unused")
+	private static class RequiresValidationBean {
+
+		public void processConstrainedValue(@Max(99) int i) {
+		}
+
+		public void processValidInput(@Valid MyInput input) {
+		}
+
+		public void processValidatedInput(@Validated MyInput input) {
+		}
+
+		public void processInputWithConstrainedValue(MyConstrainedInput input) {
+		}
+
+		public void processOptionalInputWithConstrainedValue(Optional<MyConstrainedInput> input) {
+		}
+
+		public void processValue(int i) {
+		}
+
+	}
+
+
+	private static class MyInput {
+	}
+
+	private static class MyConstrainedInput {
+
+		@Max(99)
+		private int i;
+
+		public int getI() {
+			return this.i;
+		}
+
+		public void setI(int i) {
+			this.i = i;
+		}
+
+	}
+
 }