How do I access return value of a Java method returning java.lang.String from C++ in JNI?

Question

I am trying to pass back a string from a Java method called from C++. I am not able to find out what JNI function should I call to access the method and be returned a jstrin

Answer 1

The complete working solution is as below:

Java Side

public class ClassifierWrapper {
public ClassifierWrapper(){}
public String getString() { return "TEST";}
}

Native Side

jclass cls;
jmethodID mid;
jstring rv;


cls = jniEnv->FindClass("ClassifierWrapper"); //plase also consider your package name as package\name\classname

jmethodID classifierConstructor = jniEnv->GetMethodID(cls,"", "()V");
if (classifierConstructor == NULL) {
    return NULL; /* exception thrown */
}
jobject classifierObj = jniEnv->NewObject( cls, classifierConstructor);

jmethodID getStringMethod = jniEnv->GetMethodID(cls, "getString", "()Ljava/lang/String;");

rv = (jstring)(jniEnv->CallObjectMethod(classifierObj, getStringMethod));
const char *strReturn = jniEnv->GetStringUTFChars( rv, 0);


jniEnv->ReleaseStringUTFChars(rv, strReturn);