Hi Claes,
Regarding CachedManifest I have one more comment. It's usually better to
use null/zero as "uninitialized" state for lazy-initialized fields. You
spare one (volatile) write and don't worry about unsafe publication
which might see the Java-default value instead of the one assigned in
initializer as "uninitialized". So summing-up all comments from previous
mails I would write CachedManifest class as:
private static class CachedManifest {
static final Manifest NO_MANIFEST = new Manifest();
final String fileName;
private final URL url;
private volatile Manifest manifest;
CachedManifest(final String fileName) {
this.fileName = fileName;
this.url = AccessController.doPrivileged(new
PrivilegedAction<URL>() {
public URL run() {
final File file = new File(fileName);
if (file.isFile()) {
try {
return ParseUtil.fileToEncodedURL(file);
} catch (MalformedURLException e) {
}
}
return null;
}
});
}
public URL getURL() {
return url;
}
public Manifest getManifest() {
if (url == null) return null;
Manifest m = manifest;
if (m == null) {
synchronized (this) {
if ((m = manifest) == null) {
manifest = m =
AccessController.doPrivileged(new PrivilegedAction<Manifest>() {
public Manifest run() {
try (FileInputStream fis = new
FileInputStream(fileName);
JarInputStream jis = new
JarInputStream(fis, false))
{
return jis.getManifest();
} catch (IOException e) {
return NO_MANIFEST;
}
}
});
}
}
}
return (m == NO_MANIFEST) ? null : m;
}
}
What do you say?
Regards, Peter
On 10/13/2014 04:32 PM, Peter Levart wrote:
On 10/12/2014 04:09 AM, Claes Redestad wrote:
http://cr.openjdk.java.net/~redestad/8060130/webrev.03/
Hi Claes,
First, one more nit:
1635 if (!map.containsKey(pkgName)) {
1636 map.put(pkgName, pkg);
1637 }
..could be written as:
map.putIfAbsent(pkgName, pkg);
And second, I re-read the code of CachedManifest and noticed the
following. You initialize the volatile instance field 'manifest' like
that:
609 private volatile Manifest manifest = EMPTY_MANIFEST;
So in following code:
631 public Manifest getManifest() {
632 resolveManifest();
633 return manifest;
634 }
635
636 private void resolveManifest() {
637 if (manifest != null || url == null) {
638 return;
639 }
640 synchronized(this) {
641 if (manifest == null) {
642 manifest = AccessController.doPrivileged(new
PrivilegedAction<Manifest>() {
643 public Manifest run() {
644 return loadManifest(fileName);
645 }
646 });
647 }
648 }
649 }
... loadManifest() will never be executed. getManifest() will always
return EMPTY_MANIFEST.
You probably wanted line 637 to be written as:
if (manivest != EMPTY_MANIFEST || url == null) { ...
Likewise in loadManifest(), wou write:
586 private static Manifest loadManifest(String fn) {
587 try (FileInputStream fis = new FileInputStream(fn);
588 JarInputStream jis = new JarInputStream(fis, false))
589 {
590 return jis.getManifest();
591 } catch (IOException e) {
592 return EMPTY_MANIFEST;
593 }
594 }
..but you probably wanted the line 592 to return 'null' instead.
Regards, Peter
