Polish "Allow validation api without implementation"

Closes gh-12669

Author: philwebb

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 Validator jsr303Validator;
+	private final boolean jsr303Present;
+
+	private volatile Validator jsr303Validator;
 
 	private volatile Binder binder;
 
@@ -66,7 +68,8 @@ class ConfigurationPropertiesBinder {
 				.getPropertySources();
 		this.configurationPropertiesValidator = getConfigurationPropertiesValidator(
 				applicationContext, validatorBeanName);
-
+		this.jsr303Present = ConfigurationPropertiesJsr303Validator
+				.isJsr303Present(applicationContext);
 	}
 
 	public void bind(Bindable<?> target) {
@@ -92,19 +95,23 @@ private List<Validator> getValidators(Bindable<?> target) {
 		if (this.configurationPropertiesValidator != null) {
 			validators.add(this.configurationPropertiesValidator);
 		}
-
-		if (target.getAnnotation(Validated.class) != null) {
-			this.jsr303Validator = ConfigurationPropertiesJsr303Validator.getIfJsr303Present(this.applicationContext);
-			if (this.jsr303Validator != 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.
@@ -54,7 +54,8 @@ public void validatedPropertiesTest() {
 
 	@Test
 	public void nonValidatedPropertiesTest() {
-			new AnnotationConfigApplicationContext(NonValidatedTestConfiguration.class).close();
+		new AnnotationConfigApplicationContext(NonValidatedTestConfiguration.class)
+				.close();
 	}
 
 	@EnableConfigurationProperties(TestProperties.class)
@@ -71,7 +72,6 @@ private static class TestProperties {
 
 	}
 
-
 	@EnableConfigurationProperties(NonValidatedTestProperties.class)
 	static class NonValidatedTestConfiguration {
 
@@ -84,4 +84,5 @@ static class NonValidatedTestConfiguration {
 	private static class NonValidatedTestProperties {
 
 	}
+
 }