Merge branch '3.0.x'

Closes gh-35654

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

@@ -19,6 +19,7 @@ package org.springframework.boot.context.properties.bind;
 import java.beans.Introspector;
 import java.lang.annotation.Annotation;
 import java.lang.reflect.Field;
+import java.lang.reflect.InvocationTargetException;
 import java.lang.reflect.Method;
 import java.lang.reflect.Modifier;
 import java.util.Arrays;
@@ -382,11 +383,22 @@ class JavaBeanBinder implements DataObjectBinder {
 					return this.getter.invoke(instance.get());
 				}
 				catch (Exception ex) {
+					if (isUninitializedKotlinProperty(ex)) {
+						return null;
+					}
 					throw new IllegalStateException("Unable to get value for property " + this.name, ex);
 				}
 			};
 		}
 
+		private boolean isUninitializedKotlinProperty(Exception ex) {
+			if (ex instanceof InvocationTargetException ite) {
+				return "kotlin.UninitializedPropertyAccessException"
+					.equals(ite.getTargetException().getClass().getName());
+			}
+			return false;
+		}
+
 		boolean isSettable() {
 			return this.setter != null;
 		}

spring-boot-project/spring-boot/src/test/kotlin/org/springframework/boot/context/properties/KotlinConfigurationPropertiesTests.kt

@@ -1,10 +1,30 @@
+/*
+ * Copyright 2012-2023 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.boot.context.properties
 
+import org.junit.jupiter.api.AfterEach
 import org.junit.jupiter.api.Test
 import org.springframework.beans.factory.support.BeanDefinitionRegistry
 import org.springframework.beans.factory.support.RootBeanDefinition
 import org.springframework.context.annotation.AnnotationConfigApplicationContext
 import org.springframework.context.annotation.Configuration
+import org.springframework.test.context.support.TestPropertySourceUtils
+
+import org.assertj.core.api.Assertions.assertThat
 
 /**
  * Tests for {@link ConfigurationProperties @ConfigurationProperties}-annotated beans.
@@ -15,24 +35,74 @@ class KotlinConfigurationPropertiesTests {
 
 	private var context = AnnotationConfigApplicationContext()
 
+	@AfterEach
+	fun cleanUp() {
+		this.context.close();
+	}
+
 	@Test //gh-18652
 	fun `type with constructor binding and existing singleton should not fail`() {
 		val beanFactory = this.context.beanFactory
 		(beanFactory as BeanDefinitionRegistry).registerBeanDefinition("foo",
 				RootBeanDefinition(BingProperties::class.java))
 		beanFactory.registerSingleton("foo", BingProperties(""))
-		this.context.register(TestConfig::class.java)
+		this.context.register(EnableConfigProperties::class.java)
 		this.context.refresh();
 	}
 
+	@Test
+	fun `type with constructor bound lateinit property can be bound`() {
+		this.context.register(EnableLateInitProperties::class.java)
+		TestPropertySourceUtils.addInlinedPropertiesToEnvironment(this.context, "lateinit.inner.value=alpha");
+		this.context.refresh();
+		assertThat(this.context.getBean(LateInitProperties::class.java).inner.value).isEqualTo("alpha")
+	}
+
+	@Test
+	fun `type with constructor bound lateinit property with default can be bound`() {
+		this.context.register(EnableLateInitPropertiesWithDefault::class.java)
+		TestPropertySourceUtils.addInlinedPropertiesToEnvironment(this.context, "lateinit-with-default.inner.bravo=two");
+		this.context.refresh();
+		val properties = this.context.getBean(LateInitPropertiesWithDefault::class.java)
+		assertThat(properties.inner.alpha).isEqualTo("apple")
+		assertThat(properties.inner.bravo).isEqualTo("two")
+	}
+
 	@ConfigurationProperties(prefix = "foo")
 	class BingProperties(@Suppress("UNUSED_PARAMETER") bar: String) {
 
 	}
 
-	@Configuration(proxyBeanMethods = false)
 	@EnableConfigurationProperties
-	internal open class TestConfig {
+	class EnableConfigProperties {
+
+	}
+
+	@ConfigurationProperties("lateinit")
+	class LateInitProperties {
+
+		lateinit var inner: Inner
+
+	}
+
+	data class Inner(val value: String)
+
+	@EnableConfigurationProperties(LateInitPropertiesWithDefault::class)
+	class EnableLateInitPropertiesWithDefault {
+
+	}
+
+	@ConfigurationProperties("lateinit-with-default")
+	class LateInitPropertiesWithDefault {
+
+		lateinit var inner: InnerWithDefault
+
+	}
+
+	data class InnerWithDefault(val alpha: String = "apple", val bravo: String = "banana")
+
+	@EnableConfigurationProperties(LateInitProperties::class)
+	class EnableLateInitProperties {
 
 	}