Only validate target values on zero depth

Update `ValidationBindHandler` so that validation only occurs when a
value is bound, or the bind depth is zero. This prevents validation from
triggering getters which may throw an exception.

Fixes gh-12227

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/context/properties/bind/validation/ValidationBindHandler.java

@@ -69,7 +69,7 @@ public class ValidationBindHandler extends AbstractBindHandler {
 	@Override
 	public void onFinish(ConfigurationPropertyName name, Bindable<?> target,
 			BindContext context, Object result) throws Exception {
-		validate(name, target, result);
+		validate(name, target, context, result);
 		if (context.getDepth() == 0 && !this.exceptions.isEmpty()) {
 			throw this.exceptions.pop();
 		}
@@ -77,17 +77,18 @@ public class ValidationBindHandler extends AbstractBindHandler {
 	}
 
 	private void validate(ConfigurationPropertyName name, Bindable<?> target,
-			Object result) {
-		Object validationTarget = getValidationTarget(target, result);
+			BindContext context, Object result) {
+		Object validationTarget = getValidationTarget(target, context, result);
 		Class<?> validationType = target.getBoxedType().resolve();
 		validate(name, validationTarget, validationType);
 	}
 
-	private Object getValidationTarget(Bindable<?> target, Object result) {
+	private Object getValidationTarget(Bindable<?> target, BindContext context,
+			Object result) {
 		if (result != null) {
 			return result;
 		}
-		if (target.getValue() != null) {
+		if (context.getDepth() == 0 && target.getValue() != null) {
 			return target.getValue().get();
 		}
 		return null;

spring-boot-project/spring-boot/src/test/java/org/springframework/boot/context/properties/bind/validation/ValidationBindHandlerTests.java

@@ -153,6 +153,19 @@ public class ValidationBindHandlerTests {
 						this.handler));
 	}
 
+	@Test
+	public void bindShouldNotValidateDepthGreaterThanZero() {
+		// gh-12227
+		MockConfigurationPropertySource source = new MockConfigurationPropertySource();
+		source.put("foo.bar", "baz");
+		this.sources.add(source);
+		ExampleValidatedBeanWithGetterException existingValue = new ExampleValidatedBeanWithGetterException();
+		this.binder.bind(ConfigurationPropertyName.of("foo"),
+				Bindable.of(ExampleValidatedBeanWithGetterException.class)
+						.withExistingValue(existingValue),
+				this.handler);
+	}
+
 	private BindValidationException bindAndExpectValidationError(Runnable action) {
 		try {
 			action.run();
@@ -244,6 +257,16 @@ public class ValidationBindHandlerTests {
 		public void setAddress(String address) {
 			this.address = address;
 		}
+
+	}
+
+	@Validated
+	public static class ExampleValidatedBeanWithGetterException {
+
+		public int getAge() {
+			throw new RuntimeException();
+		}
+
 	}
 
 }