Merge pull request #29890 from making:support-biconsumer-validator

* gh-29890:
  Polish contribution
  Introduce functional factory methods in Validator

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

@@ -0,0 +1,63 @@
+/*
+ * 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.validation;
+
+import java.util.function.BiConsumer;
+import java.util.function.Predicate;
+
+import org.springframework.util.Assert;
+
+/**
+ * Validator instance returned by {@link Validator#forInstanceOf(Class, BiConsumer)}
+ * and {@link Validator#forType(Class, BiConsumer)}.
+ *
+ * @author Toshiaki Maki
+ * @author Arjen Poutsma
+ * @since 6.1
+ * @param <T> the target object type
+ */
+final class TypedValidator<T> implements Validator {
+
+	private final Class<T> targetClass;
+
+	private final Predicate<Class<?>> supports;
+
+	private final BiConsumer<T, Errors> validate;
+
+
+	public TypedValidator(Class<T> targetClass, Predicate<Class<?>> supports, BiConsumer<T, Errors> validate) {
+		Assert.notNull(targetClass, "TargetClass must not be null");
+		Assert.notNull(supports, "Supports function must not be null");
+		Assert.notNull(validate, "Validate function must not be null");
+
+		this.targetClass = targetClass;
+		this.supports = supports;
+		this.validate = validate;
+	}
+
+
+	@Override
+	public boolean supports(Class<?> clazz) {
+		return this.supports.test(clazz);
+	}
+
+	@Override
+	public void validate(Object target, Errors errors) {
+		this.validate.accept(this.targetClass.cast(target), errors);
+	}
+
+}

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2021 the original author or authors.
+ * 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.
@@ -16,6 +16,8 @@
 
 package org.springframework.validation;
 
+import java.util.function.BiConsumer;
+
 /**
  * A validator for application-specific objects.
  *
@@ -26,39 +28,33 @@ package org.springframework.validation;
  * of an application, and supports the encapsulation of validation
  * logic as a first-class citizen in its own right.
  *
- * <p>Find below a simple but complete {@code Validator}
+ * <p>Implementations can be created via the static factory methods
- * implementation, which validates that the various {@link String}
+ * {@link #forInstanceOf(Class, BiConsumer)} or
- * properties of a {@code UserLogin} instance are not empty
+ * {@link #forType(Class, BiConsumer)}.
- * (that is they are not {@code null} and do not consist
+ * Below is a simple but complete {@code Validator} that validates that the
+ * various {@link String} properties of a {@code UserLogin} instance are not
+ * empty (they are not {@code null} and do not consist
  * wholly of whitespace), and that any password that is present is
  * at least {@code 'MINIMUM_PASSWORD_LENGTH'} characters in length.
  *
- * <pre class="code">public class UserLoginValidator implements Validator {
+ * <pre class="code">Validator userLoginValidator = Validator.forInstance(UserLogin.class, (login, errors) -> {
- *
+ *   ValidationUtils.rejectIfEmptyOrWhitespace(errors, "userName", "field.required");
- *    private static final int MINIMUM_PASSWORD_LENGTH = 6;
+ *   ValidationUtils.rejectIfEmptyOrWhitespace(errors, "password", "field.required");
- *
+ *   if (login.getPassword() != null
- *    public boolean supports(Class clazz) {
+ *         &amp;&amp; login.getPassword().trim().length() &lt; MINIMUM_PASSWORD_LENGTH) {
- *       return UserLogin.class.isAssignableFrom(clazz);
+ *      errors.rejectValue("password", "field.min.length",
- *    }
+ *            new Object[]{Integer.valueOf(MINIMUM_PASSWORD_LENGTH)},
- *
+ *            "The password must be at least [" + MINIMUM_PASSWORD_LENGTH + "] characters in length.");
- *    public void validate(Object target, Errors errors) {
+ *   }
- *       ValidationUtils.rejectIfEmptyOrWhitespace(errors, "userName", "field.required");
+ * });</pre>
- *       ValidationUtils.rejectIfEmptyOrWhitespace(errors, "password", "field.required");
- *       UserLogin login = (UserLogin) target;
- *       if (login.getPassword() != null
- *             &amp;&amp; login.getPassword().trim().length() &lt; MINIMUM_PASSWORD_LENGTH) {
- *          errors.rejectValue("password", "field.min.length",
- *                new Object[]{Integer.valueOf(MINIMUM_PASSWORD_LENGTH)},
- *                "The password must be at least [" + MINIMUM_PASSWORD_LENGTH + "] characters in length.");
- *       }
- *    }
- * }</pre>
  *
  * <p>See also the Spring reference manual for a fuller discussion of
  * the {@code Validator} interface and its role in an enterprise
  * application.
  *
  * @author Rod Johnson
+ * @author Toshiaki Maki
+ * @author Arjen Poutsma
  * @see SmartValidator
  * @see Errors
  * @see ValidationUtils
@@ -92,4 +88,54 @@ public interface Validator {
 	 */
 	void validate(Object target, Errors errors);
 
+
+	/**
+	 * Return a {@code Validator} that checks whether the target object
+	 * {@linkplain Class#isAssignableFrom(Class) is an instance of}
+	 * {@code targetClass}, resorting to {@code delegate} to populate
+	 * {@link Errors} if it is.
+	 *
+	 * <p>For instance:
+	 * <pre class="code">Validator passwordEqualsValidator = Validator.forInstanceOf(PasswordResetForm.class, (form, errors) -> {
+	 *   if (!Objects.equals(form.getPassword(), form.getConfirmPassword())) {
+	 * 	   errors.rejectValue("confirmPassword",
+	 * 	         "PasswordEqualsValidator.passwordResetForm.password",
+	 * 	         "password and confirm password must be same.");
+	 * 	   }
+	 * 	 });</pre>
+	 * @param targetClass the class supported by the returned validator
+	 * @param delegate function invoked with the target object, if it is an
+	 * instance of type T
+	 * @param <T> the target object type
+	 * @return the created {@code Validator}
+	 * @since 6.1
+	 */
+	static <T> Validator forInstanceOf(Class<T> targetClass, BiConsumer<T, Errors> delegate) {
+		return new TypedValidator<>(targetClass, targetClass::isAssignableFrom, delegate);
+	}
+
+	/**
+	 * Return a {@code Validator} that checks whether the target object's class
+	 * is identical to {@code targetClass}, resorting to {@code delegate} to
+	 * populate {@link Errors} if it is.
+	 *
+	 * <p>For instance:
+	 * <pre class="code">Validator passwordEqualsValidator = Validator.forType(PasswordResetForm.class, (form, errors) -> {
+	 *   if (!Objects.equals(form.getPassword(), form.getConfirmPassword())) {
+	 * 	   errors.rejectValue("confirmPassword",
+	 * 	         "PasswordEqualsValidator.passwordResetForm.password",
+	 * 	         "password and confirm password must be same.");
+	 * 	   }
+	 * 	 });</pre>
+	 * @param targetClass the exact class supported by the returned validator (no subclasses)
+	 * @param delegate function invoked with the target object, if it is an
+	 * instance of type T
+	 * @param <T> the target object type
+	 * @return the created {@code Validator}
+	 * @since 6.1
+	 */
+	static <T> Validator forType(Class<T> targetClass, BiConsumer<T, Errors> delegate) {
+		return new TypedValidator<>(targetClass, targetClass::equals, delegate);
+	}
+
 }

spring-context/src/test/java/org/springframework/validation/DataBinderTests.java

@@ -82,6 +82,16 @@ import static org.assertj.core.api.Assertions.entry;
  */
 class DataBinderTests {
 
+	private final Validator spouseValidator = Validator.forInstanceOf(TestBean.class, (tb, errors) -> {
+				if (tb == null || "XXX".equals(tb.getName())) {
+					errors.rejectValue("", "SPOUSE_NOT_AVAILABLE");
+					return;
+				}
+				if (tb.getAge() < 32) {
+					errors.rejectValue("age", "TOO_YOUNG", "simply too young");
+				}
+			});
+
 	@Test
 	void bindingNoErrors() throws BindException {
 		TestBean rod = new TestBean();
@@ -1144,7 +1154,6 @@ class DataBinderTests {
 		errors.setNestedPath("spouse");
 		assertThat(errors.getNestedPath()).isEqualTo("spouse.");
 		assertThat(errors.getFieldValue("age")).isEqualTo("argh");
-		Validator spouseValidator = new SpouseValidator();
 		spouseValidator.validate(tb.getSpouse(), errors);
 
 		errors.setNestedPath("");
@@ -1195,7 +1204,6 @@ class DataBinderTests {
 
 		errors.setNestedPath("spouse.");
 		assertThat(errors.getNestedPath()).isEqualTo("spouse.");
-		Validator spouseValidator = new SpouseValidator();
 		spouseValidator.validate(tb.getSpouse(), errors);
 
 		errors.setNestedPath("");
@@ -1267,7 +1275,6 @@ class DataBinderTests {
 
 		errors.setNestedPath("spouse.");
 		assertThat(errors.getNestedPath()).isEqualTo("spouse.");
-		Validator spouseValidator = new SpouseValidator();
 		spouseValidator.validate(tb.getSpouse(), errors);
 
 		errors.setNestedPath("");
@@ -1332,7 +1339,6 @@ class DataBinderTests {
 		testValidator.validate(tb, errors);
 		errors.setNestedPath("spouse.");
 		assertThat(errors.getNestedPath()).isEqualTo("spouse.");
-		Validator spouseValidator = new SpouseValidator();
 		spouseValidator.validate(tb.getSpouse(), errors);
 		errors.setNestedPath("");
 
@@ -1348,7 +1354,6 @@ class DataBinderTests {
 		TestBean tb = new TestBean();
 		tb.setName("XXX");
 		Errors errors = new BeanPropertyBindingResult(tb, "tb");
-		Validator spouseValidator = new SpouseValidator();
 		spouseValidator.validate(tb, errors);
 
 		assertThat(errors.hasGlobalErrors()).isTrue();
@@ -2160,28 +2165,6 @@ class DataBinderTests {
 		}
 	}
 
-
-	private static class SpouseValidator implements Validator {
-
-		@Override
-		public boolean supports(Class<?> clazz) {
-			return TestBean.class.isAssignableFrom(clazz);
-		}
-
-		@Override
-		public void validate(@Nullable Object obj, Errors errors) {
-			TestBean tb = (TestBean) obj;
-			if (tb == null || "XXX".equals(tb.getName())) {
-				errors.rejectValue("", "SPOUSE_NOT_AVAILABLE");
-				return;
-			}
-			if (tb.getAge() < 32) {
-				errors.rejectValue("age", "TOO_YOUNG", "simply too young");
-			}
-		}
-	}
-
-
 	@SuppressWarnings("unused")
 	private static class GrowingList<E> extends AbstractList<E> {
 

spring-context/src/test/java/org/springframework/validation/ValidationUtilsTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2019 the original author or authors.
+ * 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.
@@ -19,7 +19,6 @@ package org.springframework.validation;
 import org.junit.jupiter.api.Test;
 
 import org.springframework.beans.testfixture.beans.TestBean;
-import org.springframework.lang.Nullable;
 
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.assertj.core.api.Assertions.assertThatIllegalArgumentException;
@@ -34,6 +33,10 @@ import static org.assertj.core.api.Assertions.assertThatIllegalArgumentException
  */
 public class ValidationUtilsTests {
 
+	private final Validator emptyValidator = Validator.forInstanceOf(TestBean.class, (testBean, errors) -> ValidationUtils.rejectIfEmpty(errors, "name", "EMPTY", "You must enter a name!"));
+
+	private final Validator emptyOrWhitespaceValidator = Validator.forInstanceOf(TestBean.class, (testBean, errors) -> ValidationUtils.rejectIfEmptyOrWhitespace(errors, "name", "EMPTY_OR_WHITESPACE", "You must enter a name!"));
+
 	@Test
 	public void testInvokeValidatorWithNullValidator() throws Exception {
 		TestBean tb = new TestBean();
@@ -46,14 +49,14 @@ public class ValidationUtilsTests {
 	public void testInvokeValidatorWithNullErrors() throws Exception {
 		TestBean tb = new TestBean();
 		assertThatIllegalArgumentException().isThrownBy(() ->
-				ValidationUtils.invokeValidator(new EmptyValidator(), tb, null));
+				ValidationUtils.invokeValidator(emptyValidator, tb, null));
 	}
 
 	@Test
 	public void testInvokeValidatorSunnyDay() throws Exception {
 		TestBean tb = new TestBean();
 		Errors errors = new BeanPropertyBindingResult(tb, "tb");
-		ValidationUtils.invokeValidator(new EmptyValidator(), tb, errors);
+		ValidationUtils.invokeValidator(emptyValidator, tb, errors);
 		assertThat(errors.hasFieldErrors("name")).isTrue();
 		assertThat(errors.getFieldError("name").getCode()).isEqualTo("EMPTY");
 	}
@@ -62,15 +65,14 @@ public class ValidationUtilsTests {
 	public void testValidationUtilsSunnyDay() throws Exception {
 		TestBean tb = new TestBean("");
 
-		Validator testValidator = new EmptyValidator();
 		tb.setName(" ");
 		Errors errors = new BeanPropertyBindingResult(tb, "tb");
-		testValidator.validate(tb, errors);
+		emptyValidator.validate(tb, errors);
 		assertThat(errors.hasFieldErrors("name")).isFalse();
 
 		tb.setName("Roddy");
 		errors = new BeanPropertyBindingResult(tb, "tb");
-		testValidator.validate(tb, errors);
+		emptyValidator.validate(tb, errors);
 		assertThat(errors.hasFieldErrors("name")).isFalse();
 	}
 
@@ -78,8 +80,7 @@ public class ValidationUtilsTests {
 	public void testValidationUtilsNull() throws Exception {
 		TestBean tb = new TestBean();
 		Errors errors = new BeanPropertyBindingResult(tb, "tb");
-		Validator testValidator = new EmptyValidator();
+		emptyValidator.validate(tb, errors);
-		testValidator.validate(tb, errors);
 		assertThat(errors.hasFieldErrors("name")).isTrue();
 		assertThat(errors.getFieldError("name").getCode()).isEqualTo("EMPTY");
 	}
@@ -88,8 +89,7 @@ public class ValidationUtilsTests {
 	public void testValidationUtilsEmpty() throws Exception {
 		TestBean tb = new TestBean("");
 		Errors errors = new BeanPropertyBindingResult(tb, "tb");
-		Validator testValidator = new EmptyValidator();
+		emptyValidator.validate(tb, errors);
-		testValidator.validate(tb, errors);
 		assertThat(errors.hasFieldErrors("name")).isTrue();
 		assertThat(errors.getFieldError("name").getCode()).isEqualTo("EMPTY");
 	}
@@ -115,32 +115,31 @@ public class ValidationUtilsTests {
 	@Test
 	public void testValidationUtilsEmptyOrWhitespace() throws Exception {
 		TestBean tb = new TestBean();
-		Validator testValidator = new EmptyOrWhitespaceValidator();
 
 		// Test null
 		Errors errors = new BeanPropertyBindingResult(tb, "tb");
-		testValidator.validate(tb, errors);
+		emptyOrWhitespaceValidator.validate(tb, errors);
 		assertThat(errors.hasFieldErrors("name")).isTrue();
 		assertThat(errors.getFieldError("name").getCode()).isEqualTo("EMPTY_OR_WHITESPACE");
 
 		// Test empty String
 		tb.setName("");
 		errors = new BeanPropertyBindingResult(tb, "tb");
-		testValidator.validate(tb, errors);
+		emptyOrWhitespaceValidator.validate(tb, errors);
 		assertThat(errors.hasFieldErrors("name")).isTrue();
 		assertThat(errors.getFieldError("name").getCode()).isEqualTo("EMPTY_OR_WHITESPACE");
 
 		// Test whitespace String
 		tb.setName(" ");
 		errors = new BeanPropertyBindingResult(tb, "tb");
-		testValidator.validate(tb, errors);
+		emptyOrWhitespaceValidator.validate(tb, errors);
 		assertThat(errors.hasFieldErrors("name")).isTrue();
 		assertThat(errors.getFieldError("name").getCode()).isEqualTo("EMPTY_OR_WHITESPACE");
 
 		// Test OK
 		tb.setName("Roddy");
 		errors = new BeanPropertyBindingResult(tb, "tb");
-		testValidator.validate(tb, errors);
+		emptyOrWhitespaceValidator.validate(tb, errors);
 		assertThat(errors.hasFieldErrors("name")).isFalse();
 	}
 
@@ -163,32 +162,4 @@ public class ValidationUtilsTests {
 		assertThat(errors.getFieldError("name").getDefaultMessage()).isEqualTo("msg");
 	}
 
-
-	private static class EmptyValidator implements Validator {
-
-		@Override
-		public boolean supports(Class<?> clazz) {
-			return TestBean.class.isAssignableFrom(clazz);
-		}
-
-		@Override
-		public void validate(@Nullable Object obj, Errors errors) {
-			ValidationUtils.rejectIfEmpty(errors, "name", "EMPTY", "You must enter a name!");
-		}
-	}
-
-
-	private static class EmptyOrWhitespaceValidator implements Validator {
-
-		@Override
-		public boolean supports(Class<?> clazz) {
-			return TestBean.class.isAssignableFrom(clazz);
-		}
-
-		@Override
-		public void validate(@Nullable Object obj, Errors errors) {
-			ValidationUtils.rejectIfEmptyOrWhitespace(errors, "name", "EMPTY_OR_WHITESPACE", "You must enter a name!");
-		}
-	}
-
 }

spring-context/src/test/java/org/springframework/validation/ValidatorTests.java

@@ -0,0 +1,48 @@
+/*
+ * 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.validation;
+
+import org.junit.jupiter.api.Test;
+
+import org.springframework.beans.testfixture.beans.TestBean;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * @author Arjen Poutsma
+ */
+class ValidatorTests {
+
+	@Test
+	public void testSupportsForInstanceOf() {
+		Validator validator = Validator.forInstanceOf(TestBean.class, (testBean, errors) -> {});
+		assertThat(validator.supports(TestBean.class)).isTrue();
+		assertThat(validator.supports(TestBeanSubclass.class)).isTrue();
+	}
+
+	@Test
+	public void testSupportsForType() {
+		Validator validator = Validator.forType(TestBean.class, (testBean, errors) -> {});
+		assertThat(validator.supports(TestBean.class)).isTrue();
+		assertThat(validator.supports(TestBeanSubclass.class)).isFalse();
+	}
+
+
+	private static class TestBeanSubclass extends TestBean {
+	}
+
+}