详解如何获取java中类的所有对象实例

   public class InstancesOfClass {

    /**
     * native方法 : 返回所有的实例对象
     * @param targetClass 需要查询实例的Class
     * @return
     */
    public static native Object[] getInstances(Class<?> targetClass);
    }
}

static jvmtiIterationControl JNICALL objectInstanceCallback(jlong class_tag, jlong size, jlong* tag_ptr, void* user_data) {
    *tag_ptr = 1;
    return JVMTI_ITERATION_CONTINUE;
}

JNIEXPORT jobjectArray JNICALL Java_com_liubs_findinstances_jvmti_InstancesOfClass_getInstances(JNIEnv* env, jclass clazz, jclass targetClazz) {
    JavaVM* vm;
    env->GetJavaVM(&vm);

    jvmtiEnv* jvmti;
    vm->GetEnv((void**)&jvmti, JVMTI_VERSION_1_0);

    jvmtiCapabilities capabilities = {0};
    capabilities.can_tag_objects = 1;
    jvmti->AddCapabilities(&capabilities);

    jvmti->IterateOverInstancesOfClass(targetClazz, JVMTI_HEAP_OBJECT_EITHER,
                                       objectInstanceCallback, NULL);

    jlong tag = 1;
    jint count;
    jobject* instances;
    jvmti->GetObjectsWithTags(1, &tag, &count, &instances, NULL);

    printf("Found %d objects with tag\n", count);

    // 转换 std::vector<jobject> 为 jobjectArray 并返回
    jobjectArray result = env->NewObjectArray(count, targetClazz, NULL);
    for (int i = 0; i < count; i++) {
        env->SetObjectArrayElement(result, i, instances[i]);
    }

    jvmti->Deallocate((unsigned char*)instances);
    return result;
}

public class InstancesOfClass {
    static {
        String nativeLib = null;
        String osName = System.getProperty("os.name").toLowerCase();
        if(osName.contains("mac")) {
            nativeLib = "findins.dylib";
        }else if(osName.contains("linux")) {
            nativeLib = "findins.so";
        }else if(osName.contains("windows")) {
            nativeLib = "findins.dll";
        }
        if(null == nativeLib) {
            throw new UnsupportedOperationException("不支持当前操作系统");
        }
        URL nativeLibURL = InstancesOfClass.class.getClassLoader().getResource(nativeLib);
        System.load(nativeLibURL.getPath());
    }
}

class A{}
class B{}

public class TestInstancesOfClass {

    private static <T> boolean isEqual(List<T> list, Object[] insts){
        if(null == list && null == insts){
            return true;
        }
        if(null == list || null == insts || list.size() != insts.length) {
            return false;
        }

        //先按hashcode排个序
        list.sort(Comparator.comparingInt(Object::hashCode));
        List<Object> list2 = Arrays.stream(insts).sorted(Comparator.comparingInt(Object::hashCode)).collect(Collectors.toList());

        //每一个对象一定是全等
        for(int i = 0,len=list.size();i<len ;i++) {
            if(list.get(i) != list2.get(i)) {
                return false;
            }
        }
        return true;
    }

    public static void main(String[] args) {
        int count = 10;

        List<A> insts1 = new ArrayList<>();
        for(int i = 0; i<count;i++) {
            insts1.add(new A());
        }
        Object[] insts1_find = InstancesOfClass.getInstances(A.class);
        System.out.println(insts1);
        System.out.println(Arrays.asList(insts1_find));
        System.out.println("A的所有对象实例是否一致："+isEqual(insts1,insts1_find));


        List<B> insts2 = new ArrayList<>();
        for(int i = 0; i<count;i++) {
            insts2.add(new B());
        }
        Object[] insts2_find = InstancesOfClass.getInstances(B.class);
        System.out.println(insts2);
        System.out.println(Arrays.asList(insts2_find));
        System.out.println("B的所有对象实例是否一致："+isEqual(insts2,insts2_find));
    }

}

<dependency>
   <groupId>io.github.liubsyy</groupId>
  <artifactId>FindInstancesOfClass</artifactId>
   <version>1.0.1</version>
</dependency>