在CORBA客户端/服务器应用程序中使用unsigned long（从C ++）到long（Java）？

Question

On servers side I have function which returns unsigned long value (server is written in C++), lets say:

class Sth {

private:
   CORBA::ULong u;
public:
   CORBA::ULong get()
   {
    return this.u;
   }

};

How to assign (on clients side) value returned from server to variable? I mean, theres no unsigned long in Java ... Is it possigle to assign it to long? Like this:

// corba client stuff
long var = server_obj.get();

will it be ok?

Answer 1

You have to look at the IDL mapping for that. unsigned long of OMG IDLs mapped to CORBA::ULong in C++ and to int in Java. Refer IDL to Java Mapping and IDL to C++ Mapping for more on CORBA language mappings.

Answer 2

Try using the BigInteger class in java instead of long. Theres not any other convenient way to make that conversion.

Answer 3

In many cases, you know that unsigned long will never exceed 2^31, aka MAX_LONG. Then using long in Java is okey.

In some other cases, the actual values have little meaning, as long as they are unique, eg some kind of handle. Again, you can use jlong.

In yet other cases, Java is only used as an intermediate, and if conversion from C to Java to C is correct, you don't care that there was a signed/unsigned mismatch on the way.

But if none of the above exceptions hold, you should use BigInteger or reinvent it ( bad idea )