MappingJackson2MessageConverter uses generic type

Issue: SPR-16252

Author: rstoyanchev

spring-messaging/src/main/java/org/springframework/messaging/converter/MappingJackson2MessageConverter.java

@@ -37,7 +37,9 @@
 import com.fasterxml.jackson.databind.ObjectMapper;
 import com.fasterxml.jackson.databind.SerializationFeature;
 
+import org.springframework.core.GenericTypeResolver;
 import org.springframework.core.MethodParameter;
+import org.springframework.core.ResolvableType;
 import org.springframework.lang.Nullable;
 import org.springframework.messaging.Message;
 import org.springframework.messaging.MessageHeaders;
@@ -207,7 +209,7 @@ protected boolean supports(Class<?> clazz) {
 	@Override
 	@Nullable
 	protected Object convertFromInternal(Message<?> message, Class<?> targetClass, @Nullable Object conversionHint) {
-		JavaType javaType = this.objectMapper.constructType(targetClass);
+		JavaType javaType = getJavaType(targetClass, conversionHint);
 		Object payload = message.getPayload();
 		Class<?> view = getSerializationView(conversionHint);
 		// Note: in the view case, calling withType instead of forType for compatibility with Jackson <2.5
@@ -234,6 +236,18 @@ protected Object convertFromInternal(Message<?> message, Class<?> targetClass, @
 		}
 	}
 
+	private JavaType getJavaType(Class<?> targetClass, @Nullable Object conversionHint) {
+		if (conversionHint instanceof MethodParameter) {
+			MethodParameter param = (MethodParameter) conversionHint;
+			param = param.nestedIfOptional();
+			Type genericParameterType = param.getNestedGenericParameterType();
+			Class<?> contextClass = param.getContainingClass();
+			Type type = GenericTypeResolver.resolveType(genericParameterType, contextClass);
+			return this.objectMapper.getTypeFactory().constructType(type);
+		}
+		return this.objectMapper.constructType(targetClass);
+	}
+
 	@Override
 	@Nullable
 	protected Object convertToInternal(Object payload, @Nullable MessageHeaders headers,

spring-messaging/src/test/java/org/springframework/messaging/converter/MappingJackson2MessageConverterTests.java

@@ -21,6 +21,7 @@
 import java.nio.charset.StandardCharsets;
 import java.util.Arrays;
 import java.util.HashMap;
+import java.util.List;
 import java.util.Map;
 
 import com.fasterxml.jackson.annotation.JsonView;
@@ -33,8 +34,16 @@
 import org.springframework.messaging.support.MessageBuilder;
 import org.springframework.util.MimeType;
 
-import static org.hamcrest.Matchers.*;
-import static org.junit.Assert.*;
+import static org.hamcrest.Matchers.contains;
+import static org.hamcrest.Matchers.containsString;
+import static org.hamcrest.Matchers.not;
+import static org.junit.Assert.assertArrayEquals;
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertNotNull;
+import static org.junit.Assert.assertNull;
+import static org.junit.Assert.assertThat;
+import static org.junit.Assert.assertTrue;
 
 /**
  * Test fixture for {@link org.springframework.messaging.converter.MappingJackson2MessageConverter}.
@@ -127,6 +136,20 @@ public void fromMessageValidJsonWithUnknownProperty() throws IOException {
 		assertEquals("string", myBean.getString());
 	}
 
+	@Test // SPR-16252
+	public void fromMessageToList() throws Exception {
+		MappingJackson2MessageConverter converter = new MappingJackson2MessageConverter();
+		String payload = "[1, 2, 3, 4, 5, 6, 7, 8, 9]";
+		Message<?> message = MessageBuilder.withPayload(payload.getBytes(StandardCharsets.UTF_8)).build();
+
+		Method method = getClass().getDeclaredMethod("handleList", List.class);
+		MethodParameter param = new MethodParameter(method, 0);
+		Object actual = converter.fromMessage(message, List.class, param);
+
+		assertNotNull(actual);
+		assertEquals(Arrays.asList(1L, 2L, 3L, 4L, 5L, 6L, 7L, 8L, 9L), actual);
+	}
+
 	@Test
 	public void toMessage() throws Exception {
 		MappingJackson2MessageConverter converter = new MappingJackson2MessageConverter();
@@ -217,6 +240,8 @@ public JacksonViewBean jsonViewResponse() {
 	public void jsonViewPayload(@JsonView(MyJacksonView2.class) JacksonViewBean payload) {
 	}
 
+	void handleList(List<Long> payload) {}
+
 
 	public static class MyBean {