Open CD tray using JNA in Java

Question

I know this is about JNA and not JNI, but I couldn't find a better forum to place this. And since JNA builds upon JNI, I thought I would give it a try here.
I was looking for a while to figure out how to open the CD tray using Java on Windows. After a while I came up with this solution:
1. Download the jna library (jna.rar) from [https://jna.dev.java.net/|https://jna.dev.java.net/]
2. Add this to your project (in NetBeans right click the Libraries folder in the Project view and click Add JAR/Folder, then locate the jna.jar file and add this).
3. Then, make a new Java class and name it WinMM.java, and add the following code to that file
import com.sun.jna.Library;
import com.sun.jna.Native;
interface WinMM extends Library { /* We'll make a new library */
    WinMM INSTANCE = (WinMM) Native.loadLibrary(("winmm"), WinMM.class); //Create the library from the winmm.dll file
    long mciSendStringA(String lpstrCommand, String lpstrReturnString, long uReturnLength, long hwndCallback); //Create the function we need to use to open the CD tray
}4. Now you can add the following code into a button event in another class in your app to open the CD tray:
WinMM.INSTANCE.mciSendStringA("set CDAudio door open", null, 0, 0);5. Or to close the tray:
WinMM.INSTANCE.mciSendStringA("set CDAudio door closed", null, 0, 0);6. A simple app, which opens and closes the CD tray, would look like this:
public class Main {
     * @param args the command line arguments
    public static void main(String[] args) {
    WinMM.INSTANCE.mciSendStringA("set CDAudio door open", null, 0, 0); //Open tray
    WinMM.INSTANCE.mciSendStringA("set CDAudio door closed", null, 0, 0); //Close tray
}I hope this will save someone some hours of googling. And if you really don't want to use JNA, there is a solution in [this thread|http://forum.java.sun.com/thread.jspa?threadID=566946&messageID=4103195] which might work just as well. I haven't tested it though.

Answer 1

Hi Svenni, thanks for your wonderful post! If you don't mind, I have a few questions on this. Plus, if you are feeling generous, then perhaps you could even advise me on another related topic.
To start, I set up this WinMM library exactly as you prescribed, but it doesn't seem to work for me. I think I am doing everything correct, as Netbeans didn't complain about me using any
of the classes in the jna.jar file. Everything compiles just fine, so I think I am calling everything correctly.
I thought that maybe my drive isn't being acknowledged as "cdaudio", and my goal isn't to open the drive anyways. So, I found the list of MCI commands here:
[MCI commands|http://msdn.microsoft.com/en-us/library/ms712587(VS.85).aspx]
And tried to do this:
WinMM.INSTANCE.mciSendStringA("set waveaudio audio all off", null, 0, 0);Which it seems would deactivate all audio on my system, but it does not. Unfortunately, there are no errors being thrown by doing any of this, so I really don't know where to look.
What I am trying to accomplish is to gain control of the analog volume controls. The Java Sound API apparently used to support this, but it does not seem to anymore.
I can create Source and Target data lines, and read and write to them with no problems, but for some reason I am not able to get ANY controls on any line! It does seem to
be the consensus that you can't control the analog mixer from Java, and that's why I have been researching other avenues. This has been one of them, but I just can't seem to get
it to work. I think if I could, then my problems may be solved. Well, all but the problem that the MCI command strings don't seem to have support for mute/unmute, but I may have to
deal with that seperately. In my app at the moment, I basically shell execute "sysvol32.exe -R" and leave it up to my user to set the recording level, but I'd really like to manage that through
software.
Any suggestions?