c - what is wrong with this call to the java method? -

i trying call java method code. c code listens either escape, shift, ctrl key press, calls java method telling key pressed. following snippets play role in this.

c snippet:

mid = (*env)->getmethodid(env,cls,"callback","(ljava/lang/string;)v"); env = env; if(called)     switch(param) {         case vk_control:             printf("control pressed !\n");             (*env)->callvoidmethoda(env,obj,mid,"11"); // calling java method             break;         case vk_shift:             printf("shift pressed !\n");             (*env)->callvoidmethoda(env,obj,mid,"10"); // calling java method             break;         case vk_escape:             printf("escape pressed !\n");             (*env)->callvoidmethoda(env,obj,mid,"1b"); // calling java method             break;         default:             printf("the default case\n");             break;     } 

java snippet:

public void callback(string key) {     string x = keyevent.getkeytext(integer.parseint(key, 16));     system.out.println(x); } 

when run program , press escape key on console:

escape pressed ! # # fatal error has been detected java runtime environment: # #  exception_access_violation (0xc0000005) @ pc=0x5c8b809a, pid=7588, tid=8088 # # jre version: 7.0 # java vm: java hotspot(tm) client vm (20.0-b01 mixed mode, sharing windows-x86 ) # problematic frame: # v  [jvm.dll+0x19809a] # # error report file more information saved as: # w:\undertest\netbeanscurrent\keyloggertester\build\classes\hs_err_pid7588.log # # if submit bug report, please visit: #   http://java.sun.com/webapps/bugreport/crash.jsp # 

i know calling java function wrong way, don't know wrong. output, satisfies case when press escape key , unexpected error occurs.

link log file

edit:

after answer mavroprovato still same errors.

i edited way:

(*env)->callvoidmethoda(env,obj,mid,(*env)->newstringutf(env,"1b")); 

edit:

complete code version 1

complete code version 2

the jvm crashing because jnienv used not valid one. there other issues code well.

the sun jni documentation providing information regarding threads.

here comes parts obvious:

create jni_onload function in code. called when library loaded. cache javavm pointer because valid across threads. alternative call (*env)->getjavavm in initializejnivars function prefer first one.

in initializejnivars can save obj reference calling obj = (*env)->newglobalref(obj).

in lowlevelkeyboardproc have env pointer:

attachcurrentthread(javavm *jvm, jnienv &env, null);

---

edit

ok, here code should add working, have tried myself , works. nb: have not analyzed code doing did fixes working.

add these variables among other global variables:

static javavm *javavm = null; static jmethodid callbackmethod = null; static jobject callbackobject = null; 

you can remove cls, mid, env , obj variables , use mine instead.

create jni_onload method cache javavm pointer:

jniexport jint jnicall jni_onload(javavm *jvm, void *reserved) {     jnienv *env = 0;      if ((*jvm)->getenv(jvm, (void**)&env, jni_version_1_4)) {         return jni_err;     }      javavm = jvm;      return jni_version_1_4; } 

alter initializejnivars following:

void java_keylogger_testkeys_initializejnivars(jnienv *env, jobject obj) {     jclass cls = (*env)->getobjectclass(env,obj);     callbackmethod = (*env)->getmethodid(env, cls, "callback", "(ljava/lang/string;)v");     callbackobject = (*env)->newglobalref(env, obj);     if(cls == null || callbackmethod == null) {         printf("one of them null \n");     }     called = true; } 

and in lowloevelkeyboardproc code have add following:

... wparam param = kbhook->vkcode;  jnienv *env; jint rs = (*javavm)->attachcurrentthread(javavm, (void**)&env, null); if (rs != jni_ok) {     return null; // or appropriate... } ...      case vk_escape:         printf("escape pressed !\n");         jstring message = (*env)->newstringutf(env, "1b");         (*env)->callvoidmethod(env, callbackobject, callbackmethod, message);         break; ... 

in unregisterwinhook should delete global reference objects can gc'd.

... (*env)->deleteglobalref(env, callbackobject); 

and that's it.