在使用jni调用时经常遇到数据类型转换问题，以下是char*与jString相互转换的代码：

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//java字符串转C字符串
char* jstringTostr(JNIEnv* env, jstring jstr)
{        
    char* pStr = NULL;

    jclass     jstrObj   = (*env)->FindClass(env, "java/lang/String");
    jstring    encode    = (*env)->NewStringUTF(env, "utf-8");
    jmethodID  methodId  = (*env)->GetMethodID(env, jstrObj, "getBytes", "(Ljava/lang/String;)[B");
    jbyteArray byteArray = (jbyteArray)(*env)->CallObjectMethod(env, jstr, methodId, encode);
    jsize      strLen    = (*env)->GetArrayLength(env, byteArray);
    jbyte      *jBuf     = (*env)->GetByteArrayElements(env, byteArray, JNI_FALSE);

    if (jBuf > 0)
    {
        pStr = (char*)malloc(strLen + 1);

        if (!pStr)
        {
            return NULL;
        }

        memcpy(pStr, jBuf, strLen);

        pStr[strLen] = 0;
    }

    (*env)->ReleaseByteArrayElements(env, byteArray, jBuf, 0);

    return pStr;
}

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//C字符串转java字符串
jstring strToJstring(JNIEnv* env, const char* pStr)
{
    int        strLen    = strlen(pStr);
    jclass     jstrObj   = (*env)->FindClass(env, "java/lang/String");
    jmethodID  methodId  = (*env)->GetMethodID(env, jstrObj, "", "([BLjava/lang/String;)V");
    jbyteArray byteArray = (*env)->NewByteArray(env, strLen);
    jstring    encode    = (*env)->NewStringUTF(env, "utf-8");

    (*env)->SetByteArrayRegion(env, byteArray, 0, strLen, (jbyte*)pStr);
    
    return (jstring)(*env)->NewObject(env, jstrObj, methodId, byteArray, encode);
}

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