Perhaps the other structure was expecting "const char*" rather than "const wchar_t*"?

OK, I see the problem. If you pass a Pointer, you are then responsible for ensuring Structure.write() gets called *before* the method call and that you call Structure.read() *after* the method call. When the Structure is an argument, the JNA library can automatically do that for you. When you pass the Pointer, the native memory behind the struct is probably still all zeroed, which would give you an empty description.

What you can do instead of declaring the param as Pointer, is declare an intermediate Structure from which all the other ones derive, e.g.

public static class OptionsStructure extends Structure { } public static class SERVICE_DESCRIPTION extends OptionsStructure { public String lpDescription; }

That will allow the structures to be interchangeable and still get the automatic structure read/write behavior.

BTW, I've been tinkering with launching java.exe directly as a service, but the process always seems to exit immediately. I'm not sure how to figure out why, though. I can install/uninstall directly from Java without problems, but when I try to start the service it appears that the process quits immediately (I get two event log errors - "process failed to respond" and "process timed out after 30s").