jni回调函数 c++调用java

typedef void (*app_mrcp_callback)(enum MrcpMessageCallback_E type, void* message);

int mrcp_init(app_mrcp_callback cb);

struct MrcpJoinClassParam
{
char* siteID;
int siteIDLen;
int classID;
char* userName;
int userNameLen;
char* userID;
int userIDLen;
int nodeID;
int userType;
char* password;
int passwordLen;
char* portal;
int portalLen;
int max_channels;
char* customer;
};
这个回调jni里面应该怎么写，江湖急救

c＋＋调用java可以通过放射的方式。