我是 Java 编程的新手，因此如果这听起来像一个愚蠢的问题，我提前道歉。

我正在尝试构建一个用纯 C 编写的简单应用程序，它必须创建一个 JavaVM，然后通过加载基于 AWT/Swing 的 java 代码来创建一个新窗口>.

正在关注 this技术说明 我了解到，仅在 Mac OSX 中，必须从与主线程不同的线程调用 JavaVM，以便能够创建基于 AWT 的 GUI。

因此，在我的 C 应用程序的 main 函数中，我创建了一个执行所有操作的新线程，从创建 javaVM 到创建 GUI。

由于应用程序实际上并不那么简单，我将发布一个简化版本。

主要功能:

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\n", dlerror());
    }
    else {
        printf("library JavaVM loaded\n");
    }

    /* 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;
}

线程函数:

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)

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);

              }
       });
     }
}

除了创建导致死锁或类似情况的窗口外，上述所有代码都成功执行，因为终端保持忙碌而没有任何 CPU 使用率，并且两个线程都保持 Activity 状态。

如果我注释掉有关创建窗口的行，应用程序将成功执行并退出。

这是 jstack 的输出:

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

我真的不知道我还能做什么。也许这是一个愚蠢的错误，但我对这种 Java-C 组合还不够熟练，因为这是我第一次看到它。

更新: 我已经更新了 java 代码(感谢 trashgod)，但它仍然不起作用。 我错过了什么吗？

最佳答案

我能够通过查看 Eclipse 项目如何创建其启动器来解决此问题。您需要像之前那样为 JVM 生成一个单独的线程，但是 main 方法需要启动 CFRunLoop。

对于您的特定实现可能会有一些额外的细节，但目前在我们的案例中正在使用与此类似的东西:

...
#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);
...

您可以在此处查看 Eclipse 实现:

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

关于java - OSX : JavaVM, AWT/Swing 和可能的死锁，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/8750690/