add generic typed message

Author: sonus21

rqueue-core/src/main/java/com/github/sonus21/rqueue/converter/GenericMessageConverter.java

@@ -19,6 +19,7 @@
 import static org.springframework.util.Assert.notNull;
 
 import com.github.sonus21.rqueue.utils.SerializationUtils;
+import java.lang.reflect.Field;
 import java.lang.reflect.TypeVariable;
 import java.util.Collection;
 import java.util.List;
@@ -37,8 +38,8 @@
 
 /**
  * A converter to turn the payload of a {@link Message} from serialized form to a typed String and
- * vice versa. This class does not support generic class except {@link List},even for list the
- * entries should be non generic.
+ * vice versa. Supports {@link List} and single-level generic envelope types (e.g. {@code Event<T>})
+ * where type parameters are non-generic and can be resolved from non-null field values.
  */
 @Slf4j
 public class GenericMessageConverter implements SmartMessageConverter {
@@ -137,7 +138,12 @@ private String getClassNameForCollection(String name, Collection<?> payload) {
         if (payload.isEmpty()) {
           return null;
         }
-        String itemClassName = getClassName(((List<?>) payload).get(0));
+        Object firstItem = ((List<?>) payload).get(0);
+        // Only support non-generic item classes in lists to avoid ambiguous encoding
+        if (firstItem.getClass().getTypeParameters().length > 0) {
+          return null;
+        }
+        String itemClassName = getClassName(firstItem);
         if (itemClassName == null) {
           return null;
         }
@@ -146,12 +152,40 @@ private String getClassNameForCollection(String name, Collection<?> payload) {
       return null;
     }
 
-    private String getGenericFieldBasedClassName(Class<?> clazz) {
+    private Class<?> resolveTypeVariable(Class<?> clazz, TypeVariable<?> tv, Object payload) {
+      // TypeVariable instances are scoped to the class that declares them, so
+      // field.getGenericType().equals(tv) can only match fields declared on clazz itself.
+      // Superclass fields reference their own TypeVariable instances, which are distinct objects.
+      for (Field field : clazz.getDeclaredFields()) {
+        if (field.getGenericType().equals(tv)) {
+          field.setAccessible(true);
+          try {
+            Object value = field.get(payload);
+            if (value != null) {
+              return value.getClass();
+            }
+          } catch (IllegalAccessException e) {
+            log.debug("Cannot access field {}", field.getName(), e);
+          }
+        }
+      }
+      return null;
+    }
+
+    private String getGenericFieldBasedClassName(Class<?> clazz, Object payload) {
       TypeVariable<?>[] typeVariables = clazz.getTypeParameters();
       if (typeVariables.length == 0) {
         return clazz.getName();
       }
-      return null;
+      StringBuilder sb = new StringBuilder(clazz.getName());
+      for (TypeVariable<?> tv : typeVariables) {
+        Class<?> resolved = resolveTypeVariable(clazz, tv, payload);
+        if (resolved == null || resolved.getTypeParameters().length > 0) {
+          return null;
+        }
+        sb.append('#').append(resolved.getName());
+      }
+      return sb.toString();
     }
 
     private String getClassName(Object payload) {
@@ -160,7 +194,7 @@ private String getClassName(Object payload) {
       if (payload instanceof Collection) {
         return getClassNameForCollection(name, (Collection<?>) payload);
       }
-      return getGenericFieldBasedClassName(payloadClass);
+      return getGenericFieldBasedClassName(payloadClass, payload);
     }
 
     private JavaType getTargetType(Msg msg) throws ClassNotFoundException {

rqueue-core/src/test/java/com/github/sonus21/rqueue/converter/GenericMessageConverterTest.java

@@ -116,11 +116,44 @@ void toAndFromMessageList() {
   }
 
   @Test
-  void genericMessageToReturnNull() {
+  void envelopeEventToAndFromMessage() {
+    Event<Comment> event = new Event<>("evt-1", comment);
+    Message message =
+        genericMessageConverter.toMessage(event, RqueueMessageHeaders.emptyMessageHeaders());
+    Event<Comment> fromMessage =
+        (Event<Comment>) genericMessageConverter.fromMessage(message, null);
+    assertEquals(event, fromMessage);
+  }
+
+  @Test
+  void envelopeEventWithNullPayloadToReturnNull() {
+    Event<Comment> event = new Event<>("evt-1", null);
+    Message message =
+        genericMessageConverter.toMessage(event, RqueueMessageHeaders.emptyMessageHeaders());
+    assertNull(message);
+  }
+
+  @Test
+  void envelopeEventWithInheritedTypeToAndFromMessage() {
+    // T=Notification extends Alert extends BaseAlert — runtime class is Notification,
+    // so the type parameter is resolved to Notification, not the base type.
+    Notification notification = new Notification("n-1", "hello", 42);
+    Event<Notification> event = new Event<>("evt-2", notification);
+    Message message =
+        genericMessageConverter.toMessage(event, RqueueMessageHeaders.emptyMessageHeaders());
+    Event<Notification> fromMessage =
+        (Event<Notification>) genericMessageConverter.fromMessage(message, null);
+    assertEquals(event, fromMessage);
+  }
+
+  @Test
+  void genericEnvelopeToAndFromMessage() {
     GenericTestData<Comment> data = new GenericTestData<>(10, comment);
     Message message =
         genericMessageConverter.toMessage(data, RqueueMessageHeaders.emptyMessageHeaders());
-    assertNull(message);
+    GenericTestData<Comment> fromMessage =
+        (GenericTestData<Comment>) genericMessageConverter.fromMessage(message, null);
+    assertEquals(data, fromMessage);
   }
 
   @Test
@@ -369,6 +402,15 @@ public static class MultiGenericTestDataSameType<T> extends MappingRegistrar {
     private MultiGenericTestData<T, T> multiGenericTestData;
   }
 
+  @Data
+  @NoArgsConstructor
+  @AllArgsConstructor
+  public static class Event<T> {
+
+    private String id;
+    private T payload;
+  }
+
   @Data
   @NoArgsConstructor
   @AllArgsConstructor
@@ -377,4 +419,41 @@ public static class GenericTestDataWithPredefinedType {
     private Integer index;
     private MultiGenericTestData<Comment, Email> data;
   }
+
+  // Three-level hierarchy: Notification extends Alert extends BaseAlert
+  @Data
+  @NoArgsConstructor
+  @AllArgsConstructor
+  public static class BaseAlert {
+
+    private String id;
+  }
+
+  @Data
+  @EqualsAndHashCode(callSuper = true)
+  @NoArgsConstructor
+  @AllArgsConstructor
+  public static class Alert extends BaseAlert {
+
+    private String message;
+
+    public Alert(String id, String message) {
+      super(id);
+      this.message = message;
+    }
+  }
+
+  @Data
+  @EqualsAndHashCode(callSuper = true)
+  @NoArgsConstructor
+  @AllArgsConstructor
+  public static class Notification extends Alert {
+
+    private int priority;
+
+    public Notification(String id, String message, int priority) {
+      super(id, message);
+      this.priority = priority;
+    }
+  }
 }