How to call native method with 'null' parameter

Question

I need call native method like that:

java code:

private native Object SendFiles(String strEmail, DeviceInfo info, String [] arrFiles, int cntFiles, ID idRequest);

call SendFiles();

SendFiles(strEmail, null, arrFiles, cntFiles, requestID);

and c++ code:

jobject Java_com_xxxxx_xxxxx_controller_CoreController_SendFiles(JNIEnv *pEnv, jobject obj, jstring strEmail, jobject jinfo, jobjectArray jarrFiles, jint cntFiles, jobject jidRequest){
         .........

          if(jinfo == NULL)       // here crashes !!!!!!!
             doSomething();

         ............
}

Java 'null' can be sent to c 'NULL'?

how i can do this?

Is it really there where it crashes or are you accessing jinfo elsewhere? To me it seems that doSomething is only processed if jinfo is not available, but I don't see any mechanism to avoid execution of other code? — junix, Feb 21 '13 at 21:49

score 0 · Answer 1 · edited May 23 '17 at 12:27

0

You can read up on c++ NULL checks on multiple posts, such as Checking for a null object in C++ or Checking if this is null or How do we check if a pointer is NULL pointer?

however this post seems to give the most straight-forward approach: Return a "NULL" object if search result not found

edited May 23 '17 at 12:27

Community

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answered Feb 21 '13 at 18:07

Phil

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It still doesn't explain the behavior as at least in JDK 1.7 `jobject` is defined as `typedef _jobject *jobject;` so it's not a call by reference, it's a call by pointer. And the pointer should be checkable for NULL or did I get something wrong? – junix Feb 21 '13 at 21:46

score 0 · Answer 2 · answered Feb 21 '13 at 22:33

0

jobject is a pointer datatype on the C++ side. When you pass a null object from Java, C++ receives it as a NULL pointer. It's OK to compare.

The crash probably has to do with something else. Insert some diagnostic output and debug.

answered Feb 21 '13 at 22:33

Seva Alekseyev

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How to call native method with 'null' parameter

2 Answers2