关于java：OSX：JavaVM，AWT / Swing以及可能出现死锁

OSX: JavaVM, AWT/Swing and possibly a deadlock

我对Java编程真的很陌生，因此如果这听起来像一个愚蠢的问题，我会提前道歉。

我正在尝试构建一个用普通C语言编写的简单应用程序，该应用程序必须创建JavaVM，然后通过加载基于AWT/Swing的Java代码来创建新窗口。

遵循此技术说明，我了解到仅在Mac OSX中，必须从不同于主线程的线程中调用JavaVM，以便能够基于AWT创建GUI。

因此，在C应用程序的main函数中，我创建了一个新线程，该线程执行从javaVM的创建到GUI的创建的所有操作。

由于该应用程序实际上并非如此简单，因此我将发布一个简化版本。

主功能：

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int main(int argc, char** argv)
{

// Run-time loading of JavaVM framework

void *result;

result = dlopen("/System/Library/Frameworks/JavaVM.framework/JavaVM", RTLD_LAZY);
if (!result) {
printf("can't open library JavaVM: %s\
", dlerror());
}
else {
printf("library JavaVM loaded\
");
}

/* Start the thread that runs the VM. */
pthread_t vmthread;

// create a new pthread copying the stack size of the primordial pthread
struct rlimit limit;
size_t stack_size = 0;
int rc = getrlimit(RLIMIT_STACK, &limit);
if (rc == 0) {
if (limit.rlim_cur != 0LL) {
stack_size = (size_t)limit.rlim_cur;
}
}

pthread_attr_t thread_attr;
pthread_attr_init(&thread_attr);
pthread_attr_setscope(&thread_attr, PTHREAD_SCOPE_SYSTEM);
pthread_attr_setdetachstate(&thread_attr, PTHREAD_CREATE_DETACHED);
if (stack_size > 0) {
pthread_attr_setstacksize(&thread_attr, stack_size);
}

/* Start the thread that we will start the JVM on. */
pthread_create(&vmthread, &thread_attr, startJava, (void *)&thread_data_struct);
pthread_attr_destroy(&thread_attr);

pthread_exit(NULL);

return 0;
}

线程功能：

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void *startJava(void *jvm_lib)
{

JavaVMInitArgs args;

const char* classpath = getenv("CLASSPATH");

// determine classpath
char* classpath_opt = str_printf("-Djava.class.path=%s", classpath);

JavaVMOption* option = malloc(sizeof(JavaVMOption) * 2);
option[0].optionString = classpath_opt;
option[1].optionString = str_printf("-verbose:jni");

args.version = JNI_VERSION_1_6;
args.nOptions = 2;
args.options = option;
args.ignoreUnrecognized = JNI_FALSE; // don't ignore unrecognized options

fptr_JNI_CreateJavaVM JNI_CreateJavaVM_fp = (fptr_JNI_CreateJavaVM)dl_dlsym(jvm_lib,
"JNI_CreateJavaVM");

int result = JNI_CreateJavaVM_fp(&jvm, (void**) &env, &args);
free(option);
free(classpath_opt);

// launch java code
jclass init_class = (*env)->FindClass(env,"org/classes/Loader");

jmethodID load_id = (*env)->GetStaticMethodID(env, init_class,"Load",
"(Ljava/lang/String;Lorg/classes/stuff;J)V");

(*env)->CallStaticVoidMethod(env, init_class, load_id);
}

Java代码：(已更新)

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package org.classes;

import java.awt.AWTException;
import java.awt.Component;
import java.awt.Frame;
import java.awt.image.BufferedImage;
import java.awt.EventQueue;

public class Loader {
public static void Load(String baseDir, Stuff stuff, long nativePointer)
{
EventQueue.invokeLater(new Runnable() {
public void run() {
System.loadLibrary("drawingHelperLibrary");

...
...
...

// start test window
Frame frame = new Frame();
frame.setSize(640,480);
frame.setLocation(50, 50);
frame.setVisible(true);

}
});
}
}

以上所有代码均成功执行，但创建窗口会导致死锁或类似情况，这是因为终端保持忙碌而没有占用任何CPU资源，并且两个线程均保持活动状态。

如果我注释掉有关创建窗口的几行，则应用程序将成功执行并退出。

这是jstack的输出：

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Full thread dump Java HotSpot(TM) 64-Bit Server VM (20.4-b02-402 mixed mode):

"Attach Listener" daemon prio=9 tid=1040b1800 nid=0x11b888000 waiting on condition [00000000]
java.lang.Thread.State: RUNNABLE

"Low Memory Detector" daemon prio=5 tid=103806000 nid=0x10b137000 runnable [00000000]
java.lang.Thread.State: RUNNABLE

"C2 CompilerThread1" daemon prio=9 tid=103805800 nid=0x10b034000 waiting on condition [00000000]
java.lang.Thread.State: RUNNABLE

"C2 CompilerThread0" daemon prio=9 tid=103804800 nid=0x10af31000 waiting on condition [00000000]
java.lang.Thread.State: RUNNABLE

"Signal Dispatcher" daemon prio=9 tid=103804000 nid=0x10ae2e000 runnable [00000000]
java.lang.Thread.State: RUNNABLE

"Surrogate Locker Thread (Concurrent GC)" daemon prio=5 tid=103803000 nid=0x10ad2b000 waiting on condition [00000000]
java.lang.Thread.State: RUNNABLE

"Finalizer" daemon prio=8 tid=10409b800 nid=0x10ac28000 in Object.wait() [10ac27000]
java.lang.Thread.State: WAITING (on object monitor)
at java.lang.Object.wait(Native Method)
- waiting on <7f3001300> (a java.lang.ref.ReferenceQueue$Lock)
at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:118)
- locked <7f3001300> (a java.lang.ref.ReferenceQueue$Lock)
at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:134)
at java.lang.ref.Finalizer$FinalizerThread.run(Finalizer.java:159)

"Reference Handler" daemon prio=10 tid=10409b000 nid=0x10ab25000 in Object.wait() [10ab24000]
java.lang.Thread.State: WAITING (on object monitor)
at java.lang.Object.wait(Native Method)
- waiting on <7f30011d8> (a java.lang.ref.Reference$Lock)
at java.lang.Object.wait(Object.java:485)
at java.lang.ref.Reference$ReferenceHandler.run(Reference.java:116)
- locked <7f30011d8> (a java.lang.ref.Reference$Lock)

"main" prio=5 tid=104000800 nid=0x10048d000 runnable [10048a000]
java.lang.Thread.State: RUNNABLE
at java.lang.ClassLoader$NativeLibrary.load(Native Method)
at java.lang.ClassLoader.loadLibrary0(ClassLoader.java:1827)
- locked <7f30010a8> (a java.util.Vector)
- locked <7f3001100> (a java.util.Vector)
at java.lang.ClassLoader.loadLibrary(ClassLoader.java:1724)
at java.lang.Runtime.loadLibrary0(Runtime.java:823)
- locked <7f3004e90> (a java.lang.Runtime)
at java.lang.System.loadLibrary(System.java:1045)
at sun.security.action.LoadLibraryAction.run(LoadLibraryAction.java:50)
at java.security.AccessController.doPrivileged(Native Method)
at sun.awt.NativeLibLoader.loadLibraries(NativeLibLoader.java:38)
at sun.awt.DebugHelper.<clinit>(DebugHelper.java:29)
at java.awt.Component.<clinit>(Component.java:566)
at org.classes.Loader.Load(Loader.java:69)

"VM Thread" prio=9 tid=104096000 nid=0x10aa22000 runnable

"Gang worker#0 (Parallel GC Threads)" prio=9 tid=104002000 nid=0x103504000 runnable

"Gang worker#1 (Parallel GC Threads)" prio=9 tid=104002800 nid=0x103607000 runnable

"Concurrent Mark-Sweep GC Thread" prio=9 tid=10404d000 nid=0x10a6f0000 runnable
"VM Periodic Task Thread" prio=10 tid=103817800 nid=0x10b23a000 waiting on condition

"Exception Catcher Thread" prio=10 tid=104001800 nid=0x103401000 runnable
JNI global references: 913

我真的不知道该怎么办。也许这是一个愚蠢的错误，但是我对Java-C混合并不熟练，因为这是我第一次看它。

更新：我已经更新了Java代码(感谢rashgod)，但仍然无法正常工作。
我想念什么吗？

通过查看Eclipse项目如何创建启动器，我能够解决此问题。完成后，您需要为JVM生成一个单独的线程，但是main方法需要启动CFRunLoop。

您的特定实现可能还有一些其他细节，但是在我们的案例中，与此类似的东西目前正在起作用：

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...
#include <CoreServices/CoreServices.h>

static void dummyCallback(void * info) {}
...

...
if (stack_size > 0) {
pthread_attr_setstacksize(&thread_attr, stack_size);
}

CFRunLoopRef loopRef = CFRunLoopGetCurrent();

/* Start the thread that we will start the JVM on. */
pthread_create(&vmthread, &thread_attr, startJava, (void *)&thread_data_struct);
pthread_attr_destroy(&thread_attr);

CFRunLoopSourceContext sourceContext = {
.version = 0, .info = NULL, .retain = NULL, .release = NULL,
.copyDescription = NULL, .equal = NULL, .hash = NULL,
.schedule = NULL, .cancel = NULL, .perform = &dummyCallback };

CFRunLoopSourceRef sourceRef = CFRunLoopSourceCreate(NULL, 0, &sourceContext);
CFRunLoopAddSource(loopRef, sourceRef, kCFRunLoopCommonModes);
CFRunLoopRun();
CFRelease(sourceRef);
...

您可以在此处浏览Eclipse实现：

http://git.eclipse.org/c/equinox/rt.equinox.framework.git