JNI Pass By Reference, Is it Possible?

I have a Java program that calls a C++ program to authenticate users. I would like the program to return either true or false, and if false, update a pointer to an error message variable that i then can grab from the Java program.

Another explination:

The native method would look something like this:

public native String takeInfo(String nt_domain, String nt_id, String nt_idca, String nt_password, 开发者_开发问答String &error);

I would call that method here:

boolean canLogin = takeInfo(domain, userID, "", userPass, String &error)

Then in my C++ program I would check if the user is authenticated and store it in a boolean, then if false, get the error message and update &error with it. Then return that boolean to my Java program where I could display the error or let the user through.

Any ideas?

Originally I had it so the program would return either "true" or the error message, as a jstring, but my boss would like it as described above.

There is a common technique to simulate additional out parameter by using object array in parameter.

For example.

public native String takeInfo(String nt_domain, String nt_id, String nt_idca, String nt_password, String[] error);

boolean canLogin = takeInfo(domain, userID, "", userPass, error);
if(!canLogin){
   String message = error[0];
}

There is a another way to do by returning a result object

class static TakeInfoResult{
   boolean canLogon;
   String error;
}
TakeInfoResult object = takeInfo(domain, userID, "", userPass);

In the 2nd case you will need to program more in the JNI layer.

If your scenario is as simple as you describe, why not just return NULL for the "true" case (even though this is typically backwards of what you might expect) and return a pointer to the error struct in the case something goes wrong?