Fix GenericConversionService selects incorrect converter

Signed-off-by: belljun3395 <[email protected]>

Author: belljun3395

Diff for: spring-core/src/main/java/org/springframework/core/convert/support/GenericConversionService.java

@@ -342,10 +342,50 @@ public boolean matches(TypeDescriptor sourceType, TypeDescriptor targetType) {
 		}
 
 		public boolean matchesFallback(TypeDescriptor sourceType, TypeDescriptor targetType) {
-			return (this.typeInfo.getTargetType() == targetType.getObjectType() &&
-					this.targetType.hasUnresolvableGenerics() &&
-					(!(this.converter instanceof ConditionalConverter conditionalConverter) ||
-							conditionalConverter.matches(sourceType, targetType)));
+			if (this.typeInfo.getTargetType() != targetType.getObjectType()) {
+				return false;
+			}
+
+			if (!this.targetType.hasUnresolvableGenerics()) {
+				return false;
+			}
+
+			boolean assignable = isAssignableTo(targetType.getResolvableType());
+			if (!assignable) {
+				return false;
+			}
+
+			return !(this.converter instanceof ConditionalConverter conditionalConverter) ||
+					conditionalConverter.matches(sourceType, targetType);
+		}
+
+		private boolean isAssignableTo(ResolvableType expected) {
+			return isAssignable( this.targetType, expected);
+		}
+
+		private boolean isAssignable(ResolvableType actual, ResolvableType expected) {
+			Class<?> actualResolved = actual.resolve(Object.class);
+			Class<?> expectedResolved = expected.resolve(Object.class);
+			if (!expectedResolved.isAssignableFrom(actualResolved)) {
+				return false;
+			}
+
+			ResolvableType[] actualGenerics = actual.getGenerics();
+			ResolvableType[] expectedGenerics = expected.getGenerics();
+
+			if (expectedGenerics.length != actualGenerics.length) {
+				return false;
+			}
+
+			for (int i = 0; i < expectedGenerics.length; i++) {
+				ResolvableType actualGeneric = actualGenerics[i];
+				ResolvableType expectedGeneric = expectedGenerics[i];
+				if (!isAssignable(actualGeneric, expectedGeneric)) {
+					return false;
+				}
+			}
+
+			return true;
 		}
 
 		@Override

Diff for: spring-core/src/test/java/org/springframework/core/convert/support/GenericConversionServiceTests.java

@@ -594,6 +594,19 @@ void stringToListOfMapConverterWithFallbackMatch() {
 		assertThat("foo").isEqualTo(result.get(0).get("bar"));
 	}
 
+	@Test
+	@SuppressWarnings("unchecked")
+	void stringToListOfString() {
+		conversionService.addConverter(new StringToCollectionConverter(conversionService));
+		conversionService.addConverter(new StringToListOfMapConverter());
+
+		List<String> result = (List<String>) conversionService.convert("foo,bar",
+				TypeDescriptor.valueOf(String.class),
+				TypeDescriptor.collection(List.class, TypeDescriptor.valueOf(String.class))
+		);
+
+		assertThat(result.get(0)).isEqualTo("foo");
+	}
 
 	@ExampleAnnotation(active = true)
 	public String annotatedString;
@@ -990,5 +1003,4 @@ private static class StringToListOfMapConverter implements Converter<String, Lis
 			return List.of(Map.of("bar", source));
 		}
 	}
-
 }