Passing String argument from c to java using jni - java-native-interface

Question

I am trying to call java method from C, but getting below error
Status after JNI_CreateJavaVM=<0>
restCall method found:: Avinash Kumar
Execution error : file ''
error code: 114, pc=0, call=1, seg=0
114 Attempt to access item beyond bounds of memory (Signal 11)
Target is to send String as an argument from C to Java function.
Below is the code :
#include <jni.h>
#define ENV (*env)
enum eConst
{
MAX_Options = 21 ,
MAX_LREF = 120 ,
PARSING_ERROR = -10 ,
ERROR = -999 ,
EXCEPTION_ERROR = -100 ,
OK = 1 ,
YES = 'Y' ,
NO = 'N'
};
int main()
{
jint jRet;
jstring jszRes;
static JavaVM *jvm = NULL;
static JNIEnv *env = NULL ;
JavaVMInitArgs vm_args;
JavaVMOption options[MAX_Options-1];
int optionCount=0;
options[optionCount++].optionString = "-verbose:jni,class,gc";
char *path="user/work/avikumar/";
char *class_path="user/work/avikumar/";
char path_option[2000]={'\n'};
sprintf(path_option,"-Djava.class.path=%s/MyClass.class:%s/jersey-core-1.19.jar:%s/jersey-client-1.19.jar:%s/javax.ws.rs-api-2.0-m02.jar:.",class_path,path,path,path);
options[optionCount++].optionString = path_option;
options[optionCount++].optionString = "-Xms128m";
options[optionCount++].optionString = "-Xmx512m";
options[optionCount++].optionString = "-Xss8m";
vm_args.options = options;
vm_args.nOptions = optionCount;
vm_args.version = JNI_VERSION_1_6;
vm_args.ignoreUnrecognized = JNI_FALSE;
jRet = JNI_CreateJavaVM(&jvm,(void**)&env,(void*)&vm_args);
printf("Status after JNI_CreateJavaVM=<%d>\n",jRet);
if (jRet < 0)
{
return(-4);
}
if( ENV->EnsureLocalCapacity(env, MAX_LREF) < 0)
{
printf( "\n out of memory. Program terminated\n");
(*jvm)->DestroyJavaVM(jvm);
return(-5);
}
jclass jlocClass;
jlocClass= ENV->FindClass(env, "MyClass");
if (jlocClass == NULL || (*env)->ExceptionOccurred(env))
{
printf("Can not load the main class\n");
return (-6);
}
jmethodID restCall_method;
restCall_method = ENV->GetMethodID(env, jlocClass,"restCall","(Ljava/lang/String;)V");
if( restCall_method == NULL)
{
printf("restCall method not found\n");
return (-7);
}
char *inp = "Avinash Kumar";
printf("restCall method found:: %s\n",inp);
//jstring jstr = (*env)->NewStringUTF(env,inp);
jstring jstr1=(*env)->NewStringUTF(env, "Avinash Kumar");
ENV->CallVoidMethod(env, jlocClass, restCall_method,jstr1);
(*jvm)->DestroyJavaVM(jvm);
return 0;
}
MyClass.java
class MyClass
{
public static void main(String args[])
{
System.out.println("Hello Avinash\n");
}
public void restCall(String inp)
{
System.out.println(inp+ " :: Hello Avinash from restCall\n");
}
}

Answer 1

You can't mix static/non-static context inside JNI. You have two choices.
Static method
restCall_method = ENV->GetStaticMethodID(
env, jlocClass, "restCall", "(Ljava/lang/String;)V");
...
...
...
ENV->CallStaticVoidMethod(env, jlocClass, restCall_method,jstr1);
and, inside Java
public static void restCall(String inp)
or non-static method
jmethodID init = ENV->GetMethodID(env,jlocClass, "<init>", "()V");
jobject obj_MyClass = ENV->NewObject(env,jlocClass, init);
jmethodID restCall_method;
restCall_method = ENV->GetMethodID(env, jlocClass,"restCall","(Ljava/lang/String;)V");
...
...
...
ENV->CallVoidMethod(env, obj_MyClass, restCall_method,jstr1);
and, inside Java
public void restCall(String inp)
In first case, you have to use Static family methods to get id and call target method, in second case, you have to create instance of class and use methods for object based context.