Java相当于Mono.Cecil或.NET的反射，可以访问MSIL代码

Question

I thought I'd automate error detection in future code, provided some of our code needs to explicitly release connection objects because of what we think is a bug in the Java HTTP API we use (not important which API it is).

The idea was simple: For every method on a class A, if that method makes a call to a method with a return type assignable from Response , that method should also call close() on the return value. All this without actually running any code in the class being checked.

Forgive my rant, but just to say what I don't want: I found http://asm.ow2.org/ , which provided access to the bytecode I needed, however: The API seems tailored for bytecode manipulation (no pure introspection), and it's die-hard based on the visitor pattern in a way that makes it virtually impossible to discover its workings through my IDE's autocomplete, and none of the visit*() methods really nails bytecode semantics with Java objects, but strings mixing method signature and return type signature altogether. I'm not even sure if the bytecodes have any constant defined somewhere.

I was able to make use of it though, but it was really elegant. I wonder what other libraries for Java are out there with a philosophy more similar to Mono.Cecil and .NET's own System.Reflection.MethodBody object?

Answer 1

Unfortunately, ASM and BCEL are pretty much the gold standard bytecode manipulation libraries. If you don't like them, you'll probably have to modify them yourselves or take a different approach.

Edit: Soot is another major bytecode manipulation library. You could give that a try.

I'm not too familiar with ASM and BCEL, but I've written my own tools for bytecode manipulation, available on Github. Unfortunately, they're A) written in Python, not Java, and B) barely documented.

I think the best approach would be to modify the verifier to add some extra metadata to the type. The verifier already does something similar to make sure that objects are properly initialized, so it wouldn't be hard to modify it to ensure that objects are closed, as long the closed status can be expressed statically as part of the type system (ie they're stored only in local variables before closing and not mixed with already closed objects).

Answer 2

I have been working on a Java decompiler which uses a type/metadata system based on Mono.Cecil. It might be sufficient for your needs. You can find it here .

There are a bunch of other .NET inspired APIs in there too, including a reflection API and an implementation of LINQ/DLR expression trees (w/ compiler).