我能够运行类似的代码(请查看下方),其中我有多个线程访问同一个JVM(macOS)。我正在使用pthread。
以下是几个重要的事项:
- 将线程附加到JVM(“JNI接口指针(JNIEnv)仅在当前线程中有效。如果另一个线程需要访问Java VM,则必须首先调用AttachCurrentThread()将其附加到VM并获取JNI接口指针。”)
- 加入线程
- 我认为最好还是使用互斥锁来防止多个线程被附加
main.c
#include <stdio.h>
#include <jni.h>
#include <pthread.h>
#define NUM_THREADS 6
pthread_mutex_t mutexjvm;
pthread_t threads[NUM_THREADS];
struct JVM {
JNIEnv *env;
JavaVM *jvm;
};
void invoke_class(JNIEnv* env);
void *jvmThreads(void* myJvm) {
struct JVM *myJvmPtr = (struct JVM*) myJvm;
JavaVM *jvmPtr = myJvmPtr -> jvm;
JNIEnv *env = myJvmPtr -> env;
pthread_mutex_lock (&mutexjvm);
printf("I will call JVM\n");
(*jvmPtr)->AttachCurrentThread(jvmPtr, (void**) &(env), NULL);
invoke_class( env );
(*jvmPtr)->DetachCurrentThread(jvmPtr);
pthread_mutex_unlock (&mutexjvm);
pthread_exit(NULL);
}
JNIEnv* create_vm(struct JVM *jvm)
{
JNIEnv* env;
JavaVMInitArgs vm_args;
JavaVMOption options;
options.optionString = "-Djava.class.path=./";
vm_args.options = &options;
vm_args.ignoreUnrecognized = 0;
vm_args.version = JNI_VERSION_1_6;
vm_args.nOptions = 1;
int status = JNI_CreateJavaVM(&jvm->jvm, (void**)&env, &vm_args);
if (status < 0 || !env)
printf("Error\n");
return env;
}
void invoke_class(JNIEnv* env)
{
jclass Main_class;
jmethodID fun_id;
Main_class = (*env)->FindClass(env, "Main");
fun_id = (*env)->GetStaticMethodID(env, Main_class, "fun", "()I");
(*env)->CallStaticIntMethod(env, Main_class, fun_id);
}
int main(int argc, char **argv)
{
struct JVM myJvm;
myJvm.env = create_vm(&myJvm);
if(myJvm.env == NULL)
return 1;
pthread_mutex_init(&mutexjvm, NULL);
for(int i=0; i<NUM_THREADS; i++){
pthread_create(&threads[i], NULL, jvmThreads, (void*) &myJvm);
pthread_join(threads[i], 0);
}
(*myJvm.jvm)->DestroyJavaVM(myJvm.jvm);
}
Main.java
public class Main {
public static void main(String[] args){
System.out.println("Hello, world");
}
public static int fun() {
System.out.println("From JVM");
return 0;
}
}
Makefile
all: Main.class main
Main.class: Main.java
javac Main.java
main.o: main.c
llvm-gcc -c main.c \
-I${JAVA_HOME}/include \
-I${JAVA_HOME}/include/darwin/ \
main: main.o
ld -o main -L${JAVA_HOME}/jre/lib/server/ \
-ljvm \
-rpath ${JAVA_HOME}/jre/lib/server \
-L/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.12.sdk \
-demangle -dynamic -arch x86_64 \
-macosx_version_min 10.12.0 \
-lSystem \
-rpath ${JAVA_HOME}/jre/lib/server/ \
main.o
clean:
rm -f Main.class main main.o
运行代码后,您将获得以下结果:
./main
I will call JVM
From JVM
I will call JVM
From JVM
I will call JVM
From JVM
I will call JVM
From JVM
I will call JVM
From JVM
I will call JVM
From JVM
JNIEnv
的引用并将其共享到另一个线程,这不好。http://stackoverflow.com/a/10082824/2891664 自从我使用 JNI 工作以来已经太长时间了,无法确定是否实际上导致了错误。此外,在0x0
处的访问冲突基本上是空指针异常。如果您能找到导致它的行,那就太好了。 - Radiodef