C/c++&java communicate with the video file-streaming

Use open source Communication framework AllJoyn to do equipment, service search, Discovery, communication, detailed principle reference https://allseenalliance.org/developers/learn/core/system-description/ Advertisement-discovery GStreamer for media playback.                                                             Interested students can look at the Https://github.com/europelee/AjUtil, simple multimedia file stream sharing (that is, its architecture) (AllJoyn equipment, service announcements, discovery) involves:1. Multiple native threads in JNI and Java Communication processing:jnienv, JAVA_VM, thread:jnienv cannot be co-owned by multiple native threads, that is, jnienv is unique to each thread, it is thread-related, then
for a native thread, if you need to use jnienv, you need to get it owned by JAVAVM's Attachcurrentthread method.  For example, the following set_ui_message, when the internal native thread is running, needs to notify some messages to the Java layer of Android, get_jni_env to get its own jnienv. 2.thread-specific Datadid you notice current_jni_env? If Set_ui_message is called within multiple native threads, what is pthread_getspecific in the Get_jni_env function ? current_jni_env A global variable to ensure that the Env pointer is unique for each thread ?  Normally , a global variable is shared for multiple threads within a process, but if the thread wants to own it separately, the POSIX-supplied thread-specific Data can be used, i.e. Thread-private data, so it looks like this is a global variable that all threads can use, but its value is stored separately in each thread , a thread- related data structure that uses the same name and different variable addresses. Using the Pthread_key_create function to create pthread_key_create (&current_jni_env, detach_current_thread);  

3. Code:

/* Register This thread with the VM */static jnienv *Attach_current_thread(void) {jnienv *env;  Javavmattachargs args; Gst_debug ("Attaching Thread%p", g_thread_self ()); Args.version = jni_version_1_4; Args.name = NULL;  Args.group = NULL; if ((*JAVA_VM)->attachcurrentthread (JAVA_VM, &env, &args) < 0) {Gst_error ("Failed to attach current thread  "); return NULL; } return env;} /* Retrieve The JNI environment for this thread */static jnienv *get_jni_env(void)  {jnienv *env; if (env = pthread_getspecific (current_jni_env) = = NULL) {env =Attach_current_thread(); Pthread_setspecific (current_jni_env, env); } return env;} /* Change the content of the UI ' s TextView */static voidSet_ui_message(const Gchar *message, CustomData *data) {jnienv *env = get_jni_env ();Gst_debug ("Setting Message to:%s", message); Jstring jmessage = (*env)->newstringutf (env, message); (*env)->callvoidmethod (env, Data->app, set_message_method_id, jmessage);  if ((*env)->exceptioncheck (env)) {Gst_error ("Failed to call Java method"); (*env)->exceptionclear (env); } (*ENV)->deletelocalref (env, jmessage);}

C/c++&java communicate with the video file-streaming