返回字符数组从Java到C - JNI [英] Returning char array from java to C - JNI

问题描述

我在Java中的对象存储。我的C程序存储数据（以字符数组形式）在java中。现在，我想从我的店里检索数据。我找不到任何函数调用返回我一个char数组。我怎样才能做到这一点？

I have a object store in Java. My C program stores data (in form of char array) in java. Now I wish to retrieve data from my store. I cannot find any function call that returns me an char array. How can I do this?

推荐答案

您需要使用JNI提供的各种API的一个，大概GetCharArrayElements（）。

You need to use one of the various API's provided by JNI, probably GetCharArrayElements().

下面是一个例子，从工作code取来检索从Java字节数组到C（在code是被Java调用的函数，但机制是相同的）。

Following is an example, taken from working code which retrieves a byte array from Java into C (the code is a function which is invoked by Java, but the mechanics are identical).

JNIEXPORT void JNICALL Java_xxx_jniEnqueue(JNIEnv *jep,jobject thsObj,
 jlong handle, jbyteArray jvaKey, jint jvaKeyOfs, jint jvaKeyLen, jbyteArray jvaData, jint jvaDtaOfs, jint jvaDtaLen) {
    jbyte            *jniKey,*jniData;
    jthrowable       escObj;

    jniKey=(*jep)->GetByteArrayElements(jep,jvaKey,0);
    jniData=(*jep)->GetByteArrayElements(jep,jvaData,0);
    ...
    memcpy(odp->enqpfx->Msg,jniKey+jvaKeyOfs,(vuns)jvaKeyLen);              /* key badly named Msg */
    ...
    // enqueue data using key
    if(/* enqueue failed */) {
        (*jep)->ReleaseByteArrayElements(jep,jvaKey ,jniKey ,JNI_ABORT); /* abort to not copy back */
        (*jep)->ReleaseByteArrayElements(jep,jvaData,jniData,JNI_ABORT); /* abort to not copy back */
        throwEscapeObject(jep,escObj);
        return;
        }
    (*jep)->ReleaseByteArrayElements(jep,jvaKey ,jniKey ,JNI_ABORT); /* abort to not copy back */
    (*jep)->ReleaseByteArrayElements(jep,jvaData,jniData,JNI_ABORT); /* abort to not copy back */
    }

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