JNI调用API - NoClassDefFoundError(C/Java)

Question

我试图让JNI沾沾自喜,因为我在C中有一个需要访问单个Java库函数的应用程序(没有C等价库).我编写了一个非常简单的测试程序,用于从C加载Java VM并调用静态函数并获取返回值.

不幸的是,我无法让课程正确加载.虽然它可能归结为它,但我认为我的ClassPath是正确的:当我java在同一目录中使用具有相同ClassPath 的命令时,该类加载并执行完美.

环境:
Ubuntu 8.04服务器
Java JRE和SDK 1.6
gcc

我现在的工作目录总是如此/home/me/project.

这是我运行java命令(java -Djava.class.path=/home/me/project/ -verbose my.ClassABC)时得到的:

[Loaded ...] (many loads)
[Loaded my.ClassABC from file:/home/me/project/]
Hello test
[Loaded java.lang.Shutdown from shared objects file]
[Loaded java.lang.Shutdown$Lock from shared objects file]

这是我运行C程序时得到的结果(./myClassABC):

[Loaded ...]
[Loaded my.ClassABC from file:/home/me/project/]
Exception in thread "main" java.lang.NoClassDefFoundError: my.ClassABC
Failed to get class

这是我的gcc命令行:

gcc -o myClassABC myClassABC.c -I/usr/lib/jvm/java-6-sun-1.6.0.16/include/ -I/usr/lib/jvm/java-6-sun-1.6.0.16/include/linux -L/usr/lib/jvm/java-6-sun-1.6.0.16/jre/lib/i386/server/ -ljvm

我的C代码(myClassABC.c):

int main(int argc,char **argv)
{
    JNIEnv *env;
    JavaVM *jvm;
    jint res;
    jclass cls;
    jmethodID mid;
    jstring jstr;
    jclass stringClass;
    jobjectArray args;

    JavaVMInitArgs vm_args;
    JavaVMOption options[2];
    options[0].optionString =
        "-Djava.class.path=."; // or "-Djava.class.path=/home/me/project/";
    options[1].optionString =
        "-verbose";
    vm_args.version = JNI_VERSION_1_6;
    vm_args.options = options;
    vm_args.nOptions = 2;
    vm_args.ignoreUnrecognized = JNI_FALSE;
    /* Create the Java VM */
    res = JNI_CreateJavaVM(&jvm, (void**)&env, &vm_args);

    if (res < 0) {
        fprintf(stderr, "Can't create Java VM\n");
        exit(1);
    }
    if ((*env)->ExceptionOccurred(env)) {
        (*env)->ExceptionDescribe(env);
    }

    cls = (*env)->FindClass(env,"my.ClassABC");
    if (cls == NULL) {
        if ((*env)->ExceptionOccurred(env)) {
            (*env)->ExceptionDescribe(env);
        }
        printf("Failed to get class\n");
        exit(1);
    }

    [call methods, etc.]
}

我的java代码,仅用于#$%@ s和giggles(编译为/home/me/project/my/ClassABC.class):

package my;

class ClassABC {
    public static void main(String[] args) {
        System.out.println(ClassABC.getPassword("test"));
        return;
    }

    static String getPassword(String filename)
    {
        return "Hello "+filename;
    }
}

谢谢,
Brian

Answer 1

只需更换它

cls = (*env)->FindClass(env,"my.ClassABC");

同

cls = (*env)->FindClass(env,"my/ClassABC");

你应该没事

否则尝试添加

...
JavaVMOption options[3];
...
options[2].optionString = "-verbose:jni";
...