Question

我目前正在与JNI(Java原住民接口)合作,在 Java和C++之间发送数据。在执行部分法典后,每个方法的代码总是相似的。例如:

JNIEXPORT void JNICALL Java_com_trial_jni_Receiver_setData__II(JNIEnv * env, jobject thiz, jint nativeObject, jint value)  
{  
    reinterpret_cast<Receiver *>(nativeObject)->setData(value);  
}  

JNIEXPORT void JNICALL Java_com_trial_jni_Receiver_setData__ILjava_lang_String_2(JNIEnv *env, jobject thiz, jint nativeObject, jstring value)  
{  
    reinterpret_cast<Receiver *>(nativeObject)->setData(value);  
}

由于所有法典都有类似的结构,我决定产生一套宏观办法,以自动产生所有这一守则。感谢格雷戈·帕科斯兹在这一链接中的回答: 可否对理论论调? 现在,我能够利用预处理器核实我在宏观和每段处理中采用多少参数。

但是,从前一个例子来看,我无法回避我想要的东西。附录一在称为JNI_的宏观范围内有这种方法。 METHOD。我愿这样做:

#define JNI_METHOD(package,clazz,method,...)   
    JNIEXPORT void JNICALL Java_ ##package## _ ##clazz## _ ##method##__II(JNIEnv * env, jobject thiz, jint nativeObject, SET_DECLARATION_PARAMS(__VA_ARGS__ ))   
    {   
        reinterpret_cast<clazz *>(nativeObject)->method(SET_DECLARED_PARAMS(__VA_ARGS__));   
    }  

JNI_METHOD(com_trial_jni,Receiver,setData,jint);  
JNI_METHOD(com_trial_jni,Receiver,setData,jstring);

In order to avoid having this question too long I didn t paste the declaration of SET_DECLARATION_PARAMS and SET_DECLARED_PARAMS but the first one will result in something like jint arg1 and the second in arg1 without the type.

问题在于:有没有办法为 j或Ljava_lang_String_2 for jstring创造宏观回报。请注意,无法使用扼杀装置,需要将ILjava_lang_String_2而不是II列入第二个生成的方法名称。

感谢!

Answer 1

你提供的联系在很大程度上给你必要的解决办法。考虑:

#define CONCATENATE(arg1, arg2)   CONCATENATE1(arg1, arg2)
#define CONCATENATE1(arg1, arg2)  CONCATENATE2(arg1, arg2)
#define CONCATENATE2(arg1, arg2)  arg1##arg2

#define JNI_TRANSLATE_TYPE_jint I
#define JNI_TRANSLATE_TYPE_jstring Ljava_lang_String_2

#define JNI_TRANSLATE_TYPE(T) CONCATENATE(JNI_TRANSLATE_TYPE_, T)

在VS2010年测试:

#define STRINGIZE(arg)  STRINGIZE1(arg)
#define STRINGIZE1(arg) STRINGIZE2(arg)
#define STRINGIZE2(arg) #arg

#pragma message("jint: " STRINGIZE(JNI_TRANSLATE_TYPE(jint)))
#pragma message("jstring: " STRINGIZE(JNI_TRANSLATE_TYPE(jstring)))

产出:

1>  jint: I
1>  jstring: Ljava_lang_String_2

Answer 2

You might also consider using SWIG to generate the JNI wrappers for you. It can handle and hide all the nasty code for wrapping objects with JNI, as well as many other language mappings.

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