Allow fallback on field access for argument binding

Closes gh-599

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

@@ -1514,6 +1514,10 @@ accordingly. For example:
 	}
 ----
 
+TIP: If the target object doesn't have setters, and you can't change that, you can use a
+property on `AnnotatedControllerConfigurer` to allow falling back on binding via direct
+field access.
+
 By default, if the method parameter name is available (requires the `-parameters` compiler
 flag with Java 8+ or debugging info from the compiler), it is used to look up the argument.
 If needed, you can customize the name through the annotation, e.g. `@Argument("bookInput")`.

spring-graphql/src/main/java/org/springframework/graphql/data/GraphQlArgumentBinder.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2020-2022 the original author or authors.
+ * Copyright 2020-2023 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.
@@ -17,6 +17,7 @@
 package org.springframework.graphql.data;
 
 import java.lang.reflect.Constructor;
+import java.lang.reflect.Field;
 import java.util.Collection;
 import java.util.Collections;
 import java.util.Map;
@@ -39,8 +40,10 @@ import org.springframework.core.MethodParameter;
 import org.springframework.core.ResolvableType;
 import org.springframework.core.convert.ConversionService;
 import org.springframework.core.convert.TypeDescriptor;
+import org.springframework.data.util.DirectFieldAccessFallbackBeanWrapper;
 import org.springframework.lang.Nullable;
 import org.springframework.util.ClassUtils;
+import org.springframework.util.ReflectionUtils;
 import org.springframework.validation.AbstractBindingResult;
 import org.springframework.validation.BindException;
 import org.springframework.validation.DataBinder;
@@ -78,22 +81,34 @@ public class GraphQlArgumentBinder {
 	@Nullable
 	private final SimpleTypeConverter typeConverter;
 
+	private final boolean fallBackOnDirectFieldAccess;
+
 
 	public GraphQlArgumentBinder() {
 		this(null);
 	}
 
 	public GraphQlArgumentBinder(@Nullable ConversionService conversionService) {
-		if (conversionService != null) {
-			this.typeConverter = new SimpleTypeConverter();
-			this.typeConverter.setConversionService(conversionService);
-		}
-		else {
-			//  Not thread-safe when using PropertyEditors
-			this.typeConverter = null;
-		}
+		this(conversionService, false);
 	}
 
+	public GraphQlArgumentBinder(@Nullable ConversionService conversionService, boolean fallBackOnDirectFieldAccess) {
+		this.typeConverter = initTypeConverter(conversionService);
+		this.fallBackOnDirectFieldAccess = fallBackOnDirectFieldAccess;
+	}
+
+	@Nullable
+	private static SimpleTypeConverter initTypeConverter(@Nullable ConversionService conversionService) {
+		if (conversionService == null) {
+			//  Not thread-safe when using PropertyEditors
+			return null;
+		}
+		SimpleTypeConverter typeConverter = new SimpleTypeConverter();
+		typeConverter.setConversionService(conversionService);
+		return typeConverter;
+	}
+
+
 
 	/**
 	 * Add a {@link DataBinder} consumer that initializes the binder instance
@@ -297,11 +312,18 @@ public class GraphQlArgumentBinder {
 			ArgumentsBindingResult bindingResult) {
 
 		Object target = BeanUtils.instantiateClass(constructor);
-		BeanWrapper beanWrapper = PropertyAccessorFactory.forBeanPropertyAccess(target);
+		BeanWrapper beanWrapper = (this.fallBackOnDirectFieldAccess ?
+				new DirectFieldAccessFallbackBeanWrapper(target) : PropertyAccessorFactory.forBeanPropertyAccess(target));
 
 		for (Map.Entry<String, Object> entry : rawMap.entrySet()) {
 			String key = entry.getKey();
 			TypeDescriptor typeDescriptor = beanWrapper.getPropertyTypeDescriptor(key);
+			if (typeDescriptor == null && this.fallBackOnDirectFieldAccess) {
+				Field field = ReflectionUtils.findField(beanWrapper.getWrappedClass(), key);
+				if (field != null) {
+					typeDescriptor = new TypeDescriptor(field);
+				}
+			}
 			if (typeDescriptor == null) {
 				// Ignore unknown property
 				continue;

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

@@ -139,6 +139,8 @@ public class AnnotatedControllerConfigurer implements ApplicationContextAware, I
 
 	private final FormattingConversionService conversionService = new DefaultFormattingConversionService();
 
+	private boolean fallBackOnDirectFieldAccess;
+
 	private final List<HandlerMethodArgumentResolver> customArgumentResolvers = new ArrayList<>(8);
 
 	@Nullable
@@ -167,6 +169,17 @@ public class AnnotatedControllerConfigurer implements ApplicationContextAware, I
 		registrar.registerFormatters(this.conversionService);
 	}
 
+	/**
+	 * Whether binding GraphQL arguments onto
+	 * {@link org.springframework.graphql.data.method.annotation.Argument @Argument}
+	 * should falls back to direct field access in case the target object does
+	 * not use accessor methods.
+	 * @since 1.2
+	 */
+	public void setFallBackOnDirectFieldAccess(boolean fallBackOnDirectFieldAccess) {
+		this.fallBackOnDirectFieldAccess = fallBackOnDirectFieldAccess;
+	}
+
 	/**
 	 * Add a {@link HandlerMethodArgumentResolver} for custom controller method
 	 * arguments. Such custom resolvers are ordered after built-in resolvers
@@ -257,7 +270,10 @@ public class AnnotatedControllerConfigurer implements ApplicationContextAware, I
 			// Must be ahead of ArgumentMethodArgumentResolver
 			resolvers.addResolver(new ProjectedPayloadMethodArgumentResolver(obtainApplicationContext()));
 		}
-		GraphQlArgumentBinder argumentBinder = new GraphQlArgumentBinder(this.conversionService);
+
+		GraphQlArgumentBinder argumentBinder =
+				new GraphQlArgumentBinder(this.conversionService, this.fallBackOnDirectFieldAccess);
+
 		resolvers.addResolver(new ArgumentMethodArgumentResolver(argumentBinder));
 		resolvers.addResolver(new ArgumentsMethodArgumentResolver(argumentBinder));
 		resolvers.addResolver(new ContextValueMethodArgumentResolver());

spring-graphql/src/test/java/org/springframework/graphql/data/GraphQlArgumentBinderTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2020-2022 the original author or authors.
+ * Copyright 2020-2023 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.
@@ -17,6 +17,7 @@
 package org.springframework.graphql.data;
 
 import java.lang.reflect.Method;
+import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collections;
 import java.util.HashMap;
@@ -118,6 +119,19 @@ class GraphQlArgumentBinderTests {
 		assertThat(((ItemListHolder) result).getItems()).hasSize(0);
 	}
 
+	@Test // gh-599
+	void dataBindingWithDirectFieldAccess() throws Exception {
+
+		Object result = bind(
+				new GraphQlArgumentBinder(new DefaultFormattingConversionService(), true /* fallBackOnFieldAccess */),
+				"{\"items\":[{\"name\":\"first\"},{\"name\":\"second\"}]}",
+				ResolvableType.forClass(DirectFieldAccessItemListHolder.class));
+
+		assertThat(result).isNotNull().isInstanceOf(DirectFieldAccessItemListHolder.class);
+		DirectFieldAccessItemListHolder holder = (DirectFieldAccessItemListHolder) result;
+		assertThat(holder.items).hasSize(2).extracting("name").containsExactly("first", "second");
+	}
+
 	@Test // gh-349
 	void dataBindingToBeanWithEnumGenericType() throws Exception {
 
@@ -389,14 +403,19 @@ class GraphQlArgumentBinderTests {
 		assertThat(input.enums()).hasSize(2).containsExactly(FancyEnum.ONE, FancyEnum.TWO);
 	}
 
-	@SuppressWarnings("unchecked")
 	@Nullable
 	private Object bind(String json, ResolvableType targetType) throws Exception {
+		return bind(this.binder, json, targetType);
+	}
+
+	@SuppressWarnings("unchecked")
+	@Nullable
+	private Object bind(GraphQlArgumentBinder binder, String json, ResolvableType targetType) throws Exception {
 		DataFetchingEnvironment environment =
 				DataFetchingEnvironmentImpl.newDataFetchingEnvironment()
 						.arguments(this.mapper.readValue("{\"key\":" + json + "}", Map.class))
 						.build();
-		return this.binder.bind(environment, "key", targetType);
+		return binder.bind(environment, "key", targetType);
 	}
 
 
@@ -607,6 +626,17 @@ class GraphQlArgumentBinderTests {
 	}
 
 
+	static class DirectFieldAccessItemListHolder {
+
+		private List<Item> items = new ArrayList<>();
+
+		public DirectFieldAccessItemListHolder addItem(Item item) {
+			this.items.add(item);
+			return this;
+		}
+	}
+
+
 	@SuppressWarnings("unused")
 	static class Item {