我需要通过POSIX消息队列来传达Java应用程序和C进程，我想使用JNA来完成它。
经过一些研究，阅读和帮助后，我开始尝试创建一个消息队列的简单Java应用程序。
/** Simple example of JNA interface mapping and usage. */
public class HelloJNAWorld {
// This is the standard, stable way of mapping, which supports extensive
// customization and mapping of Java to native types.
public interface IPCLibrary extends Library {
IPCLibrary INSTANCE = (IPCLibrary)
Native.loadLibrary("c",IPCLibrary.class);
int msgget(NativeLong key, int msgflg);
}
public static void main(String[] args) {
int id = IPCLibrary.INSTANCE.msgget(new NativeLong(12500), 0600|1);
if(id<0){
System.out.println("Error creating message queue. Id:"+id);
System.out.println(Native.getLastError());
}else{
System.out.println("Message queue id:" + idCola);
}
}
}
我认为msgctl是最简单的地图绘制方法，因为它只是int msgget(key_t key, int msgflag);。我假设我可以将key_t映射为NativeLong，但msget返回-1。所以我检查了lastError，返回的值是2，这意味着“没有这样的文件或
目录“根据errno代码。
key_ t应该以另一种方式映射？也许我需要更多的库或类似的东西？
答案 0 :(得分：1)
由于没有人回答这个问题，有些人可能需要那些日子我需要的帮助，我在这里发布我的测试类代码。 ： - ）
import com.sun.jna.Library;
import com.sun.jna.Native;
import com.sun.jna.NativeLong;
import com.sun.jna.Platform;
import com.sun.jna.Structure;
/** Simple example of JNA interface mapping and usage. */
public class HelloJNAWorld {
// This is the standard, stable way of mapping, which supports extensive
// customization and mapping of Java to native types.
public interface CLibrary extends Library {
CLibrary INSTANCE = (CLibrary)
Native.loadLibrary((Platform.isWindows() ? "msvcrt" : "c"),CLibrary.class);
void printf(String format, Object... args);
}
public interface IPCLibrary extends Library {
IPCLibrary INSTANCE = (IPCLibrary)
Native.loadLibrary("c",IPCLibrary.class);
class WaitQueue extends Structure{
}
// mapping msqid_ds structure
class MsqidDs extends Structure{
long msg_stime; /* last msgsnd time */
long msg_rtime; /* last msgrcv time */
long msg_ctime; /* last change time */
short msg_cbytes;
short msg_qnum;
short msg_qbytes; /* max number of bytes on queue */
short msg_lspid; /* pid of last msgsnd */
short msg_lrpid; /* last receive pid */
}
// END mapping msqid_ds structure
class MsgBuf extends Structure{
NativeLong mtype; /* type of message */
byte mtext[] = new byte[1];
}
class MyMsgBuf extends MsgBuf{
public NativeLong messageKind;
public byte[] contenido = new byte[1024];
}
// Initialize queue, or if it exists, get it
int msgget(NativeLong key, int msgflg);
// Send messages to queue
// int msgsnd(int msqid, struct msgbuf *ptrkey, int length, int flag);
int msgsnd(int msqid, MsgBuf ptrkey, int msgsz, int msgflg);
// Receive messages from queue
// int msgrcv(int msqid, struct msgbuf *ptrkey, int length, long msgtype, int flag);
int msgrcv(int msqid, MsgBuf ptrkey, int length, long msgtype, int flag);
}
public static void main(String[] args) {
int idCola = IPCLibrary.INSTANCE.msgget(new NativeLong(12500), 0);
if(idCola<0){
System.out.println("The queue can't be created. IdCola:"+idCola);
System.out.println("Error msgget: " + Native.getLastError());
}else{
System.out.println("Queue with id:" + idCola + "has been recovered");
// Send message
IPCLibrary.MyMsgBuf mensaje = new IPCLibrary.MyMsgBuf();
mensaje.tipoMensaje = new NativeLong(1);
mensaje.contenido = "Sending message".getBytes();
int devSend = IPCLibrary.INSTANCE.msgsnd(idCola, mensaje, mensaje.contenido.length, 1);
if(devSend != 0){
System.out.println("Send response: "+devSend);
System.out.println("Error value: " + Native.getLastError());
}
}
// Receiving message
IPCLibrary.MyMsgBuf mensajeRecibido = new IPCLibrary.MyMsgBuf();
int bytesRecibidos = IPCLibrary.INSTANCE.msgrcv(idCola, mensajeRecibido, mensajeRecibido.contenido.length, 1234, 0);
if(bytesRecibidos > 0){
System.out.println("C message has been received: " + new String(mensajeRecibido.contenido));
}else{
System.out.println("msgrcv error: " + Native.getLastError());
}
// Send closing message
IPCLibrary.MyMsgBuf mensajeCierre = new IPCLibrary.MyMsgBuf();
mensajeCierre.tipoMensaje = new NativeLong(2);
mensajeCierre.contenido = "Closing queue".getBytes();
int devSend = IPCLibrary.INSTANCE.msgsnd(idCola, mensajeCierre, mensajeCierre.contenido.length, 1);
if(devSend != 0){
System.out.println("Send response: "+devSend);
System.out.println("Error value: " + Native.getLastError());
}
}
}
我真的希望这可以帮助别人。
答案 1 :(得分：0)
我清理了你的代码并让它运行起来。 你需要两个任务。一个发送，一个接收。 只需使用下面的main（）替换上一篇文章中的main（）即可。它对我有用。感谢您为我开始努力。 另请参阅kirk.c和spock.c以获得一个好的例子http://beej.us/guide/bgipc/output/html/multipage/mq.html
public static void main(String[] args) {
double SLEEP_MINUTES = 0.1;
int IPC_CREAT = 01000; // starts with 0 so its octal or 512
int IPC_EXCL = 02000;
int IPC_NOWAIT = 04000;
int MSG_EXCEPT = 020000;
int MSG_NOERROR = 010000; // truncate the message if its to big
int msgflg_msgrcv = MSG_NOERROR; // truncate the message if its to big
int msgflg_msgget = 0666 | IPC_CREAT;
int msgflg_msgsnd = 0;
int msgtype_msgrcv = 0; // read them all
NativeLong msgtype_msgsnd = new NativeLong(1); // just needs to be a positive number
NativeLong msgkey = new NativeLong(12500);
int msqid = IPCLibrary.INSTANCE.msgget(msgkey, msgflg_msgget);
if(msqid<0)
{
System.out.println("The queue can't be created. msqid:"+msqid);
System.out.println("Error msgget: " + Native.getLastError());
System.exit(0);
}
System.out.println("Queue with id:" + msqid + "has been found or created");
for(int i=0;i<100;i++)
{
// Send message
IPCLibrary.MyMsgBuf message = new IPCLibrary.MyMsgBuf();
message.messagetype = msgtype_msgsnd;
message.content = ("Sending message"+i+'\0').getBytes(); // add 1 for the '\0'
int devSend = IPCLibrary.INSTANCE.msgsnd(msqid, message, message.content.length+1,
msgflg_msgsnd);
if(devSend != 0)
{
System.out.println("Send response: "+devSend);
System.out.println("Error value: " + Native.getLastError());
System.exit(0);
}
System.out.println("Sent "+i);
try
{
Thread.sleep((long)(SLEEP_MINUTES*60.0*1000.0));
}
catch (InterruptedException e)
{
System.out.println("InterruptedException while writing");
System.out.println(e.getMessage());
}
}
}
public static void main(String[] args) {
// found these in /usr/include/bits/*.h
int IPC_CREAT = 01000; // remember if it starts with a '0' its octal or 512
int IPC_EXCL = 02000;
int IPC_NOWAIT = 04000;
int MSG_EXCEPT = 020000;
int MSG_NOERROR = 010000; // truncate the message if its to big
int msgflg_msgrcv = MSG_NOERROR; // truncate the message if its to big
int msgflg_msgget = 0666 | IPC_CREAT; // create the queue if its not there , let everybody read and write
int msgtype_msgrcv = 0; // read them all
NativeLong msgtype_msgsnd = new NativeLong(1); // just needs to be a positive number
NativeLong msgkey = new NativeLong(12500);
int msqid = IPCLibrary.INSTANCE.msgget(msgkey, msgflg_msgget);
if(msqid<0)
{
System.out.println("The queue can't be created. msqid:"+msqid);
System.out.println("Error msgget: " + Native.getLastError());
System.exit(0);
}
System.out.println("Queue with id:" + msqid + "has been found or was created");
for(int i=0;i<100;i++)
{
IPCLibrary.MyMsgBuf message = new IPCLibrary.MyMsgBuf();
int ret = IPCLibrary.INSTANCE.msgrcv(msqid, message, message.content.length,
msgtype_msgrcv,msgflg_msgrcv);
if(ret > 0)
{
System.out.println("message has been received: " + ret);
System.out.println(new String(message.content));
}
else
{
System.out.println("msgrcv error: " + Native.getLastError());
}
}
}
}