[jira] [Created] (THRIFT-2531) Generate Interface for thrift objects

["Jeremiah (JIRA)" <ji...@apache.org>]

Jeremiah created THRIFT-2531:
--------------------------------

             Summary: Generate Interface for thrift objects
                 Key: THRIFT-2531
                 URL: https://issues.apache.org/jira/browse/THRIFT-2531
             Project: Thrift
          Issue Type: Improvement
          Components: Java - Compiler
    Affects Versions: 0.9.1, 0.7
         Environment: Java 6
            Reporter: Jeremiah


Currently, generated thrift objects implement the TBase interface, which defines generic methods applicable to all generated objects (read/write from protocol objects, retrieving a field value by specifying the field ID).

My request is for the generation of an interface for each thrift object, which in turn implement that interface. It looks like what is already done for thrift services:

{code}
public class MyType implements org.apache.thrift.TBase<MyType, MyType._Fields>, MyType.IFace, ... {
  public interface IFace {
    ...
  }
  ...
}
{code}

The interface should contain all getters and setters for the fields specified in the thrift definition (e.g. {{getXXX()}}, {{setXXX(...)}}, {{isXXXSet()}}, etc.).
All those methods are already generated for thrift objects, they just should also be declared in an interface for each object.

*Rationale*
This will allow to use Java's dynamic proxies to decorate and manipulate thrift objects.
Java's reflective framework ({{Proxy}} and {{InvocationHandler}}) work with interfaces and are not able to manage classes as proxyed types. E.g. it is not possible to cast a proxy for an instance of {{MyType}} to a variable of type {{MyType}} if {{MyType}} is not an interface.

Thus, if the class {{MyType}} defines getters and setters, the user will not be able to use them behind a dynamic proxy as casting the proxy to {{MyType}} will throw a {{ClassCastException}}.

{code}
public interface MyIFace { ... }
public class MyClass implements MyIFace { ... }
{code}
{code}
// proxify(MyClass instance) is implemented somewhere
// The proxy has to declare proxying for an interface (MyIFace) or it won't even compile.

MyIFace f = (MyIFace) proxify(new MyClass()) // OK
MyClass x = (MyClass) proxify(new MyClass()) // Throws ClassCastException
{code}



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