Consistent processing of binding/validation failures for data classes

Includes an extension of SmartValidator for candidate value validation, as well as nullability refinements in Validator and BindingResult.

Issue: SPR-16840
Issue: SPR-16841
Issue: SPR-16854

Author: jhoeller

spring-context/src/main/java/org/springframework/validation/AbstractBindingResult.java

@@ -222,7 +222,7 @@ public Object getFieldValue(String field) {
 		if (fieldError != null) {
 			Object value = fieldError.getRejectedValue();
 			// Do not apply formatting on binding failures like type mismatches.
-			return (fieldError.isBindingFailure() ? value : formatFieldValue(field, value));
+			return (fieldError.isBindingFailure() || getTarget() == null ? value : formatFieldValue(field, value));
 		}
 		else if (getTarget() != null) {
 			Object value = getActualFieldValue(fixedField(field));
@@ -321,9 +321,8 @@ public String[] resolveMessageCodes(String errorCode) {
 
 	@Override
 	public String[] resolveMessageCodes(String errorCode, @Nullable String field) {
-		Class<?> fieldType = (getTarget() != null ? getFieldType(field) : null);
 		return getMessageCodesResolver().resolveMessageCodes(
-				errorCode, getObjectName(), fixedField(field), fieldType);
+				errorCode, getObjectName(), fixedField(field), getFieldType(field));
 	}
 
 	@Override
@@ -332,7 +331,7 @@ public void addError(ObjectError error) {
 	}
 
 	@Override
-	public void recordFieldValue(String field, Class<?> type, Object value) {
+	public void recordFieldValue(String field, Class<?> type, @Nullable Object value) {
 		this.fieldTypes.put(field, type);
 		this.fieldValues.put(field, value);
 	}

spring-context/src/main/java/org/springframework/validation/BindException.java

@@ -275,7 +275,7 @@ public void addError(ObjectError error) {
 	}
 
 	@Override
-	public void recordFieldValue(String field, Class<?> type, Object value) {
+	public void recordFieldValue(String field, Class<?> type, @Nullable Object value) {
 		this.bindingResult.recordFieldValue(field, type, value);
 	}
 

spring-context/src/main/java/org/springframework/validation/BindingResult.java

@@ -143,7 +143,7 @@ public interface BindingResult extends Errors {
 	 * @param value the original value
 	 * @since 5.0.4
 	 */
-	default void recordFieldValue(String field, Class<?> type, Object value) {
+	default void recordFieldValue(String field, Class<?> type, @Nullable Object value) {
 	}
 
 	/**

spring-context/src/main/java/org/springframework/validation/DataBinder.java

@@ -853,25 +853,34 @@ protected void applyPropertyValues(MutablePropertyValues mpvs) {
 	 * @see #getBindingResult()
 	 */
 	public void validate() {
+		Object target = getTarget();
+		Assert.state(target != null, "No target to validate");
+		BindingResult bindingResult = getBindingResult();
+		// Call each validator with the same binding result
 		for (Validator validator : this.validators) {
-			validator.validate(getTarget(), getBindingResult());
+			validator.validate(target, bindingResult);
 		}
 	}
 
 	/**
 	 * Invoke the specified Validators, if any, with the given validation hints.
 	 * <p>Note: Validation hints may get ignored by the actual target Validator.
 	 * @param validationHints one or more hint objects to be passed to a {@link SmartValidator}
+	 * @since 3.1
 	 * @see #setValidator(Validator)
 	 * @see SmartValidator#validate(Object, Errors, Object...)
 	 */
 	public void validate(Object... validationHints) {
+		Object target = getTarget();
+		Assert.state(target != null, "No target to validate");
+		BindingResult bindingResult = getBindingResult();
+		// Call each validator with the same binding result
 		for (Validator validator : getValidators()) {
 			if (!ObjectUtils.isEmpty(validationHints) && validator instanceof SmartValidator) {
-				((SmartValidator) validator).validate(getTarget(), getBindingResult(), validationHints);
+				((SmartValidator) validator).validate(target, bindingResult, validationHints);
 			}
 			else if (validator != null) {
-				validator.validate(getTarget(), getBindingResult());
+				validator.validate(target, bindingResult);
 			}
 		}
 	}

spring-context/src/main/java/org/springframework/validation/SmartValidator.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2012 the original author or authors.
+ * Copyright 2002-2018 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.
@@ -39,11 +39,29 @@ public interface SmartValidator extends Validator {
 	 * <p>Note: Validation hints may get ignored by the actual target {@code Validator},
 	 * in which case this method should behave just like its regular
 	 * {@link #validate(Object, Errors)} sibling.
-	 * @param target the object that is to be validated (can be {@code null})
-	 * @param errors contextual state about the validation process (never {@code null})
+	 * @param target the object that is to be validated
+	 * @param errors contextual state about the validation process
 	 * @param validationHints one or more hint objects to be passed to the validation engine
-	 * @see ValidationUtils
+	 * @see javax.validation.Validator#validate(Object, Class[])
 	 */
-	void validate(@Nullable Object target, Errors errors, Object... validationHints);
+	void validate(Object target, Errors errors, Object... validationHints);
+
+	/**
+	 * Validate the supplied value for the specified field on the target type,
+	 * reporting the same validation errors as if the value would be bound to
+	 * the field on an instance of the target class.
+	 * @param targetType the target type
+	 * @param fieldName the name of the field
+	 * @param value the candidate value
+	 * @param errors contextual state about the validation process
+	 * @param validationHints one or more hint objects to be passed to the validation engine
+	 * @since 5.1
+	 * @see javax.validation.Validator#validateValue(Class, String, Object, Class[])
+	 */
+	default void validateValue(
+			Class<?> targetType, String fieldName, @Nullable Object value, Errors errors, Object... validationHints) {
+
+		throw new IllegalArgumentException("Cannot validate individual value for " + targetType);
+	}
 
 }

spring-context/src/main/java/org/springframework/validation/ValidationUtils.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2017 the original author or authors.
+ * Copyright 2002-2018 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.
@@ -45,47 +45,47 @@ public abstract class ValidationUtils {
 	/**
 	 * Invoke the given {@link Validator} for the supplied object and
 	 * {@link Errors} instance.
-	 * @param validator the {@code Validator} to be invoked (must not be {@code null})
-	 * @param obj the object to bind the parameters to
-	 * @param errors the {@link Errors} instance that should store the errors (must not be {@code null})
-	 * @throws IllegalArgumentException if either of the {@code Validator} or {@code Errors} arguments is
-	 * {@code null}, or if the supplied {@code Validator} does not {@link Validator#supports(Class) support}
-	 * the validation of the supplied object's type
+	 * @param validator the {@code Validator} to be invoked
+	 * @param target the object to bind the parameters to
+	 * @param errors the {@link Errors} instance that should store the errors
+	 * @throws IllegalArgumentException if either of the {@code Validator} or {@code Errors}
+	 * arguments is {@code null}, or if the supplied {@code Validator} does not
+	 * {@link Validator#supports(Class) support} the validation of the supplied object's type
 	 */
-	public static void invokeValidator(Validator validator, Object obj, Errors errors) {
-		invokeValidator(validator, obj, errors, (Object[]) null);
+	public static void invokeValidator(Validator validator, Object target, Errors errors) {
+		invokeValidator(validator, target, errors, (Object[]) null);
 	}
 
 	/**
 	 * Invoke the given {@link Validator}/{@link SmartValidator} for the supplied object and
 	 * {@link Errors} instance.
-	 * @param validator the {@code Validator} to be invoked (must not be {@code null})
-	 * @param obj the object to bind the parameters to
-	 * @param errors the {@link Errors} instance that should store the errors (must not be {@code null})
+	 * @param validator the {@code Validator} to be invoked
+	 * @param target the object to bind the parameters to
+	 * @param errors the {@link Errors} instance that should store the errors
 	 * @param validationHints one or more hint objects to be passed to the validation engine
-	 * @throws IllegalArgumentException if either of the {@code Validator} or {@code Errors} arguments is
-	 * {@code null}, or if the supplied {@code Validator} does not {@link Validator#supports(Class) support}
-	 * the validation of the supplied object's type
+	 * @throws IllegalArgumentException if either of the {@code Validator} or {@code Errors}
+	 * arguments is {@code null}, or if the supplied {@code Validator} does not
+	 * {@link Validator#supports(Class) support} the validation of the supplied object's type
 	 */
 	public static void invokeValidator(
-			Validator validator, @Nullable Object obj, Errors errors, @Nullable Object... validationHints) {
+			Validator validator, Object target, Errors errors, @Nullable Object... validationHints) {
 
 		Assert.notNull(validator, "Validator must not be null");
 		Assert.notNull(errors, "Errors object must not be null");
 
 		if (logger.isDebugEnabled()) {
 			logger.debug("Invoking validator [" + validator + "]");
 		}
-		if (obj != null && !validator.supports(obj.getClass())) {
+		if (!validator.supports(target.getClass())) {
 			throw new IllegalArgumentException(
-					"Validator [" + validator.getClass() + "] does not support [" + obj.getClass() + "]");
+					"Validator [" + validator.getClass() + "] does not support [" + target.getClass() + "]");
 		}
 
 		if (!ObjectUtils.isEmpty(validationHints) && validator instanceof SmartValidator) {
-			((SmartValidator) validator).validate(obj, errors, validationHints);
+			((SmartValidator) validator).validate(target, errors, validationHints);
 		}
 		else {
-			validator.validate(obj, errors);
+			validator.validate(target, errors);
 		}
 
 		if (logger.isDebugEnabled()) {

spring-context/src/main/java/org/springframework/validation/Validator.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2012 the original author or authors.
+ * Copyright 2002-2018 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.
@@ -16,8 +16,6 @@
 
 package org.springframework.validation;
 
-import org.springframework.lang.Nullable;
-
 /**
  * A validator for application-specific objects.
  *
@@ -61,6 +59,7 @@
  * application.
  *
  * @author Rod Johnson
+ * @see SmartValidator
  * @see Errors
  * @see ValidationUtils
  */
@@ -87,10 +86,10 @@ public interface Validator {
 	 * typically has (or would) return {@code true}.
 	 * <p>The supplied {@link Errors errors} instance can be used to report
 	 * any resulting validation errors.
-	 * @param target the object that is to be validated (can be {@code null})
-	 * @param errors contextual state about the validation process (never {@code null})
+	 * @param target the object that is to be validated
+	 * @param errors contextual state about the validation process
 	 * @see ValidationUtils
 	 */
-	void validate(@Nullable Object target, Errors errors);
+	void validate(Object target, Errors errors);
 
 }

spring-context/src/main/java/org/springframework/validation/beanvalidation/SpringValidatorAdapter.java

@@ -50,13 +50,17 @@
  * while also exposing the original JSR-303 Validator interface itself.
  *
  * <p>Can be used as a programmatic wrapper. Also serves as base class for
- * {@link CustomValidatorBean} and {@link LocalValidatorFactoryBean}.
+ * {@link CustomValidatorBean} and {@link LocalValidatorFactoryBean},
+ * and as the primary implementation of the {@link SmartValidator} interface.
  *
  * <p>As of Spring Framework 5.0, this adapter is fully compatible with
  * Bean Validation 1.1 as well as 2.0.
  *
  * @author Juergen Hoeller
  * @since 3.0
+ * @see SmartValidator
+ * @see CustomValidatorBean
+ * @see LocalValidatorFactoryBean
  */
 public class SpringValidatorAdapter implements SmartValidator, javax.validation.Validator {
 
@@ -99,26 +103,43 @@ public boolean supports(Class<?> clazz) {
 	}
 
 	@Override
-	public void validate(@Nullable Object target, Errors errors) {
+	public void validate(Object target, Errors errors) {
 		if (this.targetValidator != null) {
 			processConstraintViolations(this.targetValidator.validate(target), errors);
 		}
 	}
 
 	@Override
-	public void validate(@Nullable Object target, Errors errors, @Nullable Object... validationHints) {
+	public void validate(Object target, Errors errors, Object... validationHints) {
 		if (this.targetValidator != null) {
-			Set<Class<?>> groups = new LinkedHashSet<>();
-			if (validationHints != null) {
-				for (Object hint : validationHints) {
-					if (hint instanceof Class) {
-						groups.add((Class<?>) hint);
-					}
-				}
-			}
 			processConstraintViolations(
-					this.targetValidator.validate(target, ClassUtils.toClassArray(groups)), errors);
+					this.targetValidator.validate(target, asValidationGroups(validationHints)), errors);
+		}
+	}
+
+	@SuppressWarnings("unchecked")
+	@Override
+	public void validateValue(
+			Class<?> targetType, String fieldName, @Nullable Object value, Errors errors, Object... validationHints) {
+
+		if (this.targetValidator != null) {
+			processConstraintViolations(this.targetValidator.validateValue(
+					(Class) targetType, fieldName, value, asValidationGroups(validationHints)), errors);
+		}
+	}
+
+	/**
+	 * Turn the specified validation hints into JSR-303 validation groups.
+	 * @since 5.1
+	 */
+	private Class<?>[] asValidationGroups(Object... validationHints) {
+		Set<Class<?>> groups = new LinkedHashSet<>(4);
+		for (Object hint : validationHints) {
+			if (hint instanceof Class) {
+				groups.add((Class<?>) hint);
+			}
 		}
+		return ClassUtils.toClassArray(groups);
 	}
 
 	/**

spring-web/src/main/java/org/springframework/web/bind/support/WebExchangeBindException.java

@@ -261,7 +261,7 @@ public void addError(ObjectError error) {
 	}
 
 	@Override
-	public void recordFieldValue(String field, Class<?> type, Object value) {
+	public void recordFieldValue(String field, Class<?> type, @Nullable Object value) {
 		this.bindingResult.recordFieldValue(field, type, value);
 	}