Merge pull request #34183 from remeio

* pr/34183:
  Polish "Add support for multidimensional arrays"
  Add support for multidimensional arrays

Closes gh-34183

Author: snicoll

spring-beans/src/main/java/org/springframework/beans/AbstractNestablePropertyAccessor.java

@@ -904,16 +904,7 @@ private PropertyValue createDefaultPropertyValue(PropertyTokenHolder tokens) {
 	private Object newValue(Class<?> type, @Nullable TypeDescriptor desc, String name) {
 		try {
 			if (type.isArray()) {
-				Class<?> componentType = type.componentType();
-				// TODO - only handles 2-dimensional arrays
-				if (componentType.isArray()) {
-					Object array = Array.newInstance(componentType, 1);
-					Array.set(array, 0, Array.newInstance(componentType.componentType(), 0));
-					return array;
-				}
-				else {
-					return Array.newInstance(componentType, 0);
-				}
+				return createArray(type);
 			}
 			else if (Collection.class.isAssignableFrom(type)) {
 				TypeDescriptor elementDesc = (desc != null ? desc.getElementTypeDescriptor() : null);
@@ -937,6 +928,24 @@ else if (Map.class.isAssignableFrom(type)) {
 		}
 	}
 
+	/**
+	 * Create the array for the given array type.
+	 * @param arrayType the desired type of the target array
+	 * @return a new array instance
+	 */
+	private static Object createArray(Class<?> arrayType) {
+		Assert.notNull(arrayType, "Array type must not be null");
+		Class<?> componentType = arrayType.componentType();
+		if (componentType.isArray()) {
+			Object array = Array.newInstance(componentType, 1);
+			Array.set(array, 0, createArray(componentType));
+			return array;
+		}
+		else {
+			return Array.newInstance(componentType, 0);
+		}
+	}
+
 	/**
 	 * Parse the given property name into the corresponding property name tokens.
 	 * @param propertyName the property name to parse

spring-beans/src/test/java/org/springframework/beans/BeanWrapperAutoGrowingTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2024 the original author or authors.
+ * Copyright 2002-2025 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.
@@ -103,6 +103,27 @@ void getPropertyValueAutoGrow3dArray() {
 		assertThat(bean.getThreeDimensionalArray()[1][2][3]).isInstanceOf(Bean.class);
 	}
 
+	@Test
+	void getPropertyValueAutoGrow3dArrayList() {
+		assertThat(wrapper.getPropertyValue("threeDimensionalArrayList[1][2][3][4]")).isNotNull();
+		assertThat(bean.getThreeDimensionalArrayList()).hasSize(2);
+		assertThat(bean.getThreeDimensionalArrayList().get(1)).hasNumberOfRows(3);
+		assertThat(bean.getThreeDimensionalArrayList().get(1)[2]).hasNumberOfRows(4);
+		assertThat(bean.getThreeDimensionalArrayList().get(1)[2][3]).hasSize(5);
+		assertThat(bean.getThreeDimensionalArrayList().get(1)[2][3][4]).isInstanceOf(Bean.class);
+	}
+
+	@Test
+	void getPropertyValueAutoGrow3dArrayListForDefault3dArray() {
+		assertThat(wrapper.getPropertyValue("threeDimensionalArrayList[0]")).isNotNull();
+		assertThat(bean.getThreeDimensionalArrayList()).hasSize(1);
+
+		// Default 3-dimensional array should be [[[]]]
+		assertThat(bean.getThreeDimensionalArrayList().get(0)).hasNumberOfRows(1);
+		assertThat(bean.getThreeDimensionalArrayList().get(0)[0]).hasNumberOfRows(1);
+		assertThat(bean.getThreeDimensionalArrayList().get(0)[0][0]).isEmpty();
+	}
+
 	@Test
 	void setPropertyValueAutoGrow2dArray() {
 		Bean newBean = new Bean();
@@ -123,6 +144,16 @@ void setPropertyValueAutoGrow3dArray() {
 			.extracting(Bean::getProp).isEqualTo("enigma");
 	}
 
+	@Test
+	void setPropertyValueAutoGrow3dArrayList() {
+		Bean newBean = new Bean();
+		newBean.setProp("enigma");
+		wrapper.setPropertyValue("threeDimensionalArrayList[0][1][2][3]", newBean);
+		assertThat(bean.getThreeDimensionalArrayList().get(0)[1][2][3])
+				.isInstanceOf(Bean.class)
+				.extracting(Bean::getProp).isEqualTo("enigma");
+	}
+
 	@Test
 	void getPropertyValueAutoGrowList() {
 		assertThat(wrapper.getPropertyValue("list[0]")).isNotNull();
@@ -215,6 +246,8 @@ public static class Bean {
 
 		private Bean[][][] threeDimensionalArray;
 
+		private List<Bean[][][]> threeDimensionalArrayList;
+
 		private List<Bean> list;
 
 		private List<List<Bean>> nestedList;
@@ -269,6 +302,14 @@ public void setThreeDimensionalArray(Bean[][][] threeDimensionalArray) {
 			this.threeDimensionalArray = threeDimensionalArray;
 		}
 
+		public List<Bean[][][]> getThreeDimensionalArrayList() {
+			return threeDimensionalArrayList;
+		}
+
+		public void setThreeDimensionalArrayList(List<Bean[][][]> threeDimensionalArrayList) {
+			this.threeDimensionalArrayList = threeDimensionalArrayList;
+		}
+
 		public List<Bean> getList() {
 			return list;
 		}