EvanYao826 opened a new pull request, #16272:
URL: https://github.com/apache/dubbo/pull/16272
Fixes #16197
## Problem
Hessian2 deserializes all small integers as `Integer`, causing
`ClassCastException` when the expected type is `Byte`, `Short`, etc.
```java
// Consumer sends
List<Byte> byteList = List.of((byte)1, (byte)2, (byte)127);
// Provider receives
List<Integer> byteList = List.of(1, 2, 127); // ClassCastException!
```
**Root cause**: Dubbo passes only the erased `Class` (e.g., `List.class`) to
the serialization framework during request deserialization, discarding the
generic `Type` (e.g., `List<Byte>`). Hessian2 has no way to know the expected
element type.
## Fix
In `Hessian2ObjectInput.readObjectOfType()`, after deserializing with the
erased class, check if the declared type is a `ParameterizedType`. If so,
convert collection/map elements to match the declared generic type arguments.
### Changes
- `Hessian2ObjectInput.java`: Added `convertGenericType()` method that
handles:
- Collection types (`List`, `Set`) with element type conversion
- Map types with key/value type conversion
- Numeric type narrowing (`Byte`, `Short`, `Float`, `Long`, `Double`,
`Integer`)
- Both boxed and primitive number types
- `ReflectionMethodDescriptor.java`: Added `getGenericParameterTypes()`
method to expose generic type information
- `DecodeableRpcInvocation.java`: Pass generic `Type` instead of erased
`Class` to deserialization
- `Hessian2SerializationTest.java`: Added comprehensive tests for:
- `List<Byte>`, `List<Short>`, `List<Float>`, `List<Long>`, `List<Double>`
- `Map<String, Byte>`, `Map<String, Short>`
- Mixed type collections
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