Merge pull request spring-projects#12669 from geo-m

* pr/12669:
  Polish "Allow validation api without implementation"
  Allow validation api without implementation

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/context/properties/ConfigurationPropertiesBinder.java

@@ -55,7 +55,9 @@ class ConfigurationPropertiesBinder {
 
 	private final Validator configurationPropertiesValidator;
 
-	private final Validator jsr303Validator;
+	private final boolean jsr303Present;
+
+	private volatile Validator jsr303Validator;
 
 	private volatile Binder binder;
 
@@ -66,8 +68,8 @@ class ConfigurationPropertiesBinder {
 				.getPropertySources();
 		this.configurationPropertiesValidator = getConfigurationPropertiesValidator(
 				applicationContext, validatorBeanName);
-		this.jsr303Validator = ConfigurationPropertiesJsr303Validator
-				.getIfJsr303Present(applicationContext);
+		this.jsr303Present = ConfigurationPropertiesJsr303Validator
+				.isJsr303Present(applicationContext);
 	}
 
 	public void bind(Bindable<?> target) {
@@ -93,16 +95,23 @@ private List<Validator> getValidators(Bindable<?> target) {
 		if (this.configurationPropertiesValidator != null) {
 			validators.add(this.configurationPropertiesValidator);
 		}
-		if (this.jsr303Validator != null
-				&& target.getAnnotation(Validated.class) != null) {
-			validators.add(this.jsr303Validator);
+		if (this.jsr303Present && target.getAnnotation(Validated.class) != null) {
+			validators.add(getJsr303Validator());
 		}
 		if (target.getValue() != null && target.getValue().get() instanceof Validator) {
 			validators.add((Validator) target.getValue().get());
 		}
 		return validators;
 	}
 
+	private Validator getJsr303Validator() {
+		if (this.jsr303Validator == null) {
+			this.jsr303Validator = new ConfigurationPropertiesJsr303Validator(
+					this.applicationContext);
+		}
+		return this.jsr303Validator;
+	}
+
 	private BindHandler getBindHandler(ConfigurationProperties annotation,
 			List<Validator> validators) {
 		BindHandler handler = new IgnoreTopLevelConverterNotFoundBindHandler();

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/context/properties/ConfigurationPropertiesJsr303Validator.java

@@ -38,8 +38,7 @@ final class ConfigurationPropertiesJsr303Validator implements Validator {
 
 	private final Delegate delegate;
 
-	private ConfigurationPropertiesJsr303Validator(
-			ApplicationContext applicationContext) {
+	ConfigurationPropertiesJsr303Validator(ApplicationContext applicationContext) {
 		this.delegate = new Delegate(applicationContext);
 	}
 
@@ -53,15 +52,14 @@ public void validate(Object target, Errors errors) {
 		this.delegate.validate(target, errors);
 	}
 
-	public static ConfigurationPropertiesJsr303Validator getIfJsr303Present(
-			ApplicationContext applicationContext) {
+	public static boolean isJsr303Present(ApplicationContext applicationContext) {
 		ClassLoader classLoader = applicationContext.getClassLoader();
 		for (String validatorClass : VALIDATOR_CLASSES) {
 			if (!ClassUtils.isPresent(validatorClass, classLoader)) {
-				return null;
+				return false;
 			}
 		}
-		return new ConfigurationPropertiesJsr303Validator(applicationContext);
+		return true;
 	}
 
 	private static class Delegate extends LocalValidatorFactoryBean {

spring-boot-project/spring-boot/src/test/java/org/springframework/boot/diagnostics/analyzer/ValidationExceptionFailureAnalyzerTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2017 the original author or authors.
+ * Copyright 2012-2018 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.
@@ -25,6 +25,7 @@
 import org.springframework.boot.testsupport.runner.classpath.ClassPathExclusions;
 import org.springframework.boot.testsupport.runner.classpath.ModifiedClassPathRunner;
 import org.springframework.context.annotation.AnnotationConfigApplicationContext;
+import org.springframework.validation.annotation.Validated;
 
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.junit.Assert.fail;
@@ -39,7 +40,7 @@
 public class ValidationExceptionFailureAnalyzerTests {
 
 	@Test
-	public void test() {
+	public void validatedPropertiesTest() {
 		try {
 			new AnnotationConfigApplicationContext(TestConfiguration.class).close();
 			fail("Expected failure did not occur");
@@ -51,6 +52,12 @@ public void test() {
 		}
 	}
 
+	@Test
+	public void nonValidatedPropertiesTest() {
+		new AnnotationConfigApplicationContext(NonValidatedTestConfiguration.class)
+				.close();
+	}
+
 	@EnableConfigurationProperties(TestProperties.class)
 	static class TestConfiguration {
 
@@ -60,8 +67,22 @@ static class TestConfiguration {
 	}
 
 	@ConfigurationProperties("test")
+	@Validated
 	private static class TestProperties {
 
 	}
 
+	@EnableConfigurationProperties(NonValidatedTestProperties.class)
+	static class NonValidatedTestConfiguration {
+
+		NonValidatedTestConfiguration(NonValidatedTestProperties testProperties) {
+		}
+
+	}
+
+	@ConfigurationProperties("test")
+	private static class NonValidatedTestProperties {
+
+	}
+
 }