YamlPropertiesFactoryBean incorrect flatten nested map to properties

spring-beans/src/main/java/org/springframework/beans/factory/config/YamlProcessor.java

@@ -56,6 +56,7 @@
  * @author Juergen Hoeller
  * @author Sam Brannen
  * @author Brian Clozel
+ * @author Mengqi Xu
  * @since 4.1
  */
 public abstract class YamlProcessor {
@@ -244,13 +245,7 @@ private Map<String, Object> asMap(Object object) {
 			if (value instanceof Map) {
 				value = asMap(value);
 			}
-			if (key instanceof CharSequence) {
-				result.put(key.toString(), value);
-			}
-			else {
-				// It has to be a map key in this case
-				result.put("[" + key.toString() + "]", value);
-			}
+			result.put(key.toString(), value);
 		});
 		return result;
 	}
@@ -305,17 +300,20 @@ private boolean process(Map<String, Object> map, MatchCallback callback) {
 	 */
 	protected final Map<String, Object> getFlattenedMap(Map<String, Object> source) {
 		Map<String, Object> result = new LinkedHashMap<>();
-		buildFlattenedMap(result, source, null);
+		buildFlattenedMap(result, source, null, false);
 		return result;
 	}
 
 	@SuppressWarnings({"rawtypes", "unchecked"})
-	private void buildFlattenedMap(Map<String, Object> result, Map<String, Object> source, @Nullable String path) {
+	private void buildFlattenedMap(Map<String, Object> result, Map<String, Object> source, @Nullable String path, boolean isIndexedKey) {
 		source.forEach((key, value) -> {
 			if (StringUtils.hasText(path)) {
-				if (key.startsWith("[")) {
+				if (isIndexedKey) {
 					key = path + key;
 				}
+				else if (key.startsWith("[") || key.endsWith("]")) {
+					key = path + '[' + key + ']';
+				}
 				else {
 					key = path + '.' + key;
 				}
@@ -325,7 +323,7 @@ private void buildFlattenedMap(Map<String, Object> result, Map<String, Object> s
 			}
 			else if (value instanceof Map map) {
 				// Need a compound key
-				buildFlattenedMap(result, map, key);
+				buildFlattenedMap(result, map, key, false);
 			}
 			else if (value instanceof Collection collection) {
 				// Need a compound key
@@ -336,7 +334,7 @@ else if (value instanceof Collection collection) {
 					int count = 0;
 					for (Object object : collection) {
 						buildFlattenedMap(result, Collections.singletonMap(
-								"[" + (count++) + "]", object), key);
+								"[" + (count++) + "]", object), key, true);
 					}
 				}
 			}

spring-beans/src/test/java/org/springframework/beans/factory/config/YamlMapFactoryBeanTests.java

@@ -128,4 +128,18 @@ void testDuplicateKey() {
 				this.factory.getObject().get("mymap"));
 	}
 
+	@Test
+	void testMapWithIntegerKey() {
+		this.factory.setResources(new ByteArrayResource("foo:\n  1: bar".getBytes()));
+		Map<String, Object> map = this.factory.getObject();
+
+		assertThat(map).hasSize(1);
+		assertThat(map.containsKey("foo")).isTrue();
+		Object object = map.get("foo");
+		assertThat(object).isInstanceOf(LinkedHashMap.class);
+		@SuppressWarnings("unchecked")
+		Map<String, Object> sub = (Map<String, Object>) object;
+		assertThat(sub.containsKey("1")).isTrue();
+		assertThat(sub.get("1")).isEqualTo("bar");
+	}
 }

spring-beans/src/test/java/org/springframework/beans/factory/config/YamlProcessorTests.java

@@ -99,7 +99,7 @@ void mapConvertedToIndexedBeanReference() {
 	void integerKeyBehaves() {
 		setYaml("foo: bar\n1: bar");
 		this.processor.process((properties, map) -> {
-			assertThat(properties.get("[1]")).isEqualTo("bar");
+			assertThat(properties.get("1")).isEqualTo("bar");
 			assertThat(properties).hasSize(2);
 		});
 	}
@@ -108,7 +108,7 @@ void integerKeyBehaves() {
 	void integerDeepKeyBehaves() {
 		setYaml("foo:\n  1: bar");
 		this.processor.process((properties, map) -> {
-			assertThat(properties.get("foo[1]")).isEqualTo("bar");
+			assertThat(properties.get("foo.1")).isEqualTo("bar");
 			assertThat(properties).hasSize(1);
 		});
 	}

spring-beans/src/test/java/org/springframework/beans/factory/config/YamlPropertiesFactoryBeanTests.java

@@ -165,6 +165,42 @@ void loadResourceWithDefaultMatchSkippingMissedMatch() {
 		assertThat(properties.getProperty("one")).isEqualTo("two");
 	}
 
+
+	@Test // gh-27020
+	void loadResourceWithEscapedKey() {
+		String yaml = "root:\n" +
+				"  webservices:\n" +
+				"    \"[domain.test:8080]\":\n" +
+				"      - username: foo\n" +
+				"        password: bar\n";
+		YamlPropertiesFactoryBean factory = new YamlPropertiesFactoryBean();
+		factory.setResources(
+				new ByteArrayResource(yaml.getBytes()),
+				new ByteArrayResource("indexed:\n  \"[0]\": foo\n  \"[1]\": bar".getBytes()),
+				new ByteArrayResource("indexed2:\n  - \"[a]\": foo\n    \"[b]\": bar".getBytes()),
+				new ByteArrayResource("only-left-bracket:\n  \"[/key1/\": foo".getBytes()),
+				new ByteArrayResource("only-right-bracket:\n  \"/key1/]\": foo".getBytes()),
+				new ByteArrayResource("special-bracket:\n  \"][/key1/][\": foo".getBytes()),
+				new ByteArrayResource("number-key:\n  1: foo".getBytes()));
+
+		Properties properties = factory.getObject();
+		assertThat(properties.getProperty("root.webservices[[domain.test:8080]][0].username")).isEqualTo("foo");
+		assertThat(properties.getProperty("root.webservices[[domain.test:8080]][0].password")).isEqualTo("bar");
+
+		assertThat(properties.getProperty("indexed[[0]]")).isEqualTo("foo");
+		assertThat(properties.getProperty("indexed[[1]]")).isEqualTo("bar");
+
+		assertThat(properties.getProperty("indexed2[0][[a]]")).isEqualTo("foo");
+		assertThat(properties.getProperty("indexed2[0][[b]]")).isEqualTo("bar");
+
+		assertThat(properties.getProperty("only-left-bracket[[/key1/]")).isEqualTo("foo");
+		assertThat(properties.getProperty("only-right-bracket[/key1/]]")).isEqualTo("foo");
+		assertThat(properties.getProperty("special-bracket.][/key1/][")).isEqualTo("foo");
+
+		assertThat(properties.getProperty("number-key.1")).isEqualTo("foo");
+	}
+
+
 	@Test
 	void loadNonExistentResource() {
 		YamlPropertiesFactoryBean factory = new YamlPropertiesFactoryBean();