Java - Catching System.load() Errors

Question

My main():

System.out.println("Start loading libraries");
boolean b2 = false;
try{
  b2 = FileManager.loadBinaries();
} catch (Exception e){
  System.out.println("Exception on loading");
}
System.out.println("Libraries loading ended");

LoadBinaries():

public static boolean loadBinaries(){
    String os = System.getProperty("os.name").toLowerCase();
    ArrayList<String> bins = new ArrayList<String>();

    if(os.indexOf("windows 7") >= 0 || os.indexOf("windows vista") >= 0){
        bins.add("/nm/metadata/bin/win/libcurld.dll");
        bins.add("/nm/metadata/bin/win/libfftw3f-3.dll");
        bins.add("/nm/metadata/bin/win/libmad.dll");
        bins.add("/nm/metadata/bin/win/libsamplerate.dll");
        bins.add("/nm/metadata/bin/win/seven/mylib.dll");
    }
    else if(os.indexOf("windows xp") >= 0){
        bins.add("/nm/metadata/bin/win/libcurld.dll");
        bins.add("/nm/metadata/bin/win/libfftw3f-3.dll");
        bins.add("/nm/metadata/bin/win/libmad.dll");
        bins.add("/nm/metadata/bin/win/libsamplerate.dll");
        bins.add("/nm/metadata/bin/win/xp/mylib.dll");
    } else if(os.indexOf("mac") >= 0){
        return false;
    }

    File f = null;
    for(String bin : bins){
        InputStream in = FileManager.class.getResourceAsStream(bin);
        byte[] buffer = new byte[1024];
        int read = -1;
        try {
            String[] temp = bin.split("/");
            f = new File(LIB_FOLDER + "/" + temp[temp.length-1]);
            File realF = new File(f.getAbsolutePath());

            if(!realF.exists()){
                FileOutputStream fos = new FileOutputStream(realF);

                while((read = in.read(buffer)) != -1) {
                    fos.write(buffer, 0, read);
                }
                fos.close();
                in.close();
            }
            System.out.println("Hello Load");
            System.load(f.getAbsolutePath());
            System.out.println("Bye Load");
        } catch (Exception e) { System.out.println("Bye Exception"); FileManager.log(e.getMessage(), true); librariesLoaded = false; return false; }
    }

    System.out.println("Bye Method");
    librariesLoaded = true;
    return true;
}

When I run this main I get next output:

Start loading libraries
Hello Load
Bye Load
Hello Load
Bye Load
Hello Load
Bye Load
Hello Load
Bye Load
Hello Load
Exception in thread "main" java.lang.UnsatisfiedLinkError: C:\java\workspace\Lib\mylib.dll: The application has failed to start because its side-by-side configuration is incorrect. Please see the application event log for more detail
    at java.lang.ClassLoader$NativeLibrary.load(Native Method)
    at java.lang.ClassLoader.loadLibrary0(Unknown Source)
    at java.lang.ClassLoader.loadLibrary(Unknown Source)
    at java.lang.Runtime.load0(Unknown Source)
    at java.lang.System.load(Unknown Source)
    at nm.player.FileManager.loadBinaries(FileManager.java:264)
    at nm.player.Player.<init>(Player.java:88)
    at nm.player.Player.main(Player.java:523)

This error is beacause it is missing some c++ system dlls. But my problem is not this. I am concern about where the program goes after this error! I don't see the print on the catch, the print after the loop in the method and neither the prints on the main, after loadbinaries is executed.

How can I catch this type of errors and deal with them? Example: When this error occur, I want to print "please intall c++ libraries" and control the flow after it.

score 23 · Accepted Answer · answered Apr 23 '11 at 12:22

Try replacing

catch (Exception e)

at the bottom of your loadBinaries() method with

catch (UnsatisfiedLinkError e)

UnsatisfiedLinkError is a subclass of Error, which is not a subclass of Exception: Error and Exception are both subclasses of Throwable, the root of the Java exception hierarchy.

Normally, you don't catch Errors. However, it seems you have a reasonable case for doing so here, in that you can display a message to your users saying 'Library X is missing, please install it'.

Itay Maman · Answer 2 · 2011-04-23T12:30:11.583

You're getting an UnsatisfiedLinkError which is not a subclass of Exception and thus is not caught by your catch clause. If you want it to be caught change the catch to catch(Error e).

You see, Java's exception hierarchy is a bit unintuitive. You have two classes, Exception and Error, each of which extends Throwable. Thus, if you want to catch absolutely everything you need to catch Throwable (not recommended).

RuntimException, by the way, is a subclass of Exception.

score 1 · Answer 3 · edited May 23 '17 at 12:32

1

Its an error. and its good practice to not to catch the errors as per java PMD.

you can follow these link for more info

When to catch java.lang.Error?

http://pmd.sourceforge.net/rules/strictexception.html

edited May 23 '17 at 12:32

Community

1
1

answered Apr 23 '11 at 12:08

GuruKulki

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While it's a good general rule not to catch `Error` or its subclasses, this case seems to be an exception. – Joachim Sauer Apr 23 '11 at 12:56

Java - Catching System.load() Errors

3 Answers3