/**
* Locates and if necessary downloads the artifact.
*
* @param artifact the Artifact to download and locate in the cache.
* @return the File pointing to the artifact. The file may not exist if the download has failed.
*/
private File getResourceFile(Artifact artifact) throws TransitException, IOException {
CacheMonitorRouter monitor = Transit.getInstance().getCacheMonitorRouter();
if (monitor != null) {
monitor.resourceRequested(artifact);
}
if (null == artifact) {
throw new NullArgumentException("artifact");
}
String path = m_resolver.resolvePath(artifact);
File destination = new File(m_cacheDir, path);
File parentDir = destination.getParentFile();
parentDir.mkdirs();
boolean exist = destination.exists();
boolean success;
if (exist) {
success = true;
} else {
ResourceHost known = findKnownGroupHost(artifact);
success = download(known, artifact, destination);
if (!success) {
ResourceHost any = findAnyPresence(artifact);
success = download(any, artifact, destination);
}
}
if (success) {
checkInternalConsistency(artifact, destination);
endNotifyMonitor(monitor, exist, artifact, destination);
}
if (!destination.exists() && monitor != null) {
monitor.failedDownload(artifact);
}
return destination;
}
/**
* Download an artifact from a host to the cache.
*
* @param host the remote host
* @param artifact the artifact being retrieved
* @param destination the cached destination
* @return TRUE if downloaded
* @exception IOException if an IO error occurs
* @exception TransitException if a transit system error occurs
*/
private boolean download(ResourceHost host, Artifact artifact, File destination)
throws IOException, TransitException {
if (host == null) {
return false;
}
CacheMonitorRouter monitor = Transit.getInstance().getCacheMonitorRouter();
File parentDir = destination.getParentFile();
File tempFile = File.createTempFile("~dpml", ".tmp", parentDir);
tempFile.deleteOnExit(); // safety harness in case we abort abnormally
FileOutputStream tempOut = new FileOutputStream(tempFile);
try {
Date lastModified = host.download(artifact, tempOut);
// An atomic operation and no risk of a corrupted
// artifact content.
tempFile.renameTo(destination);
destination.setLastModified(lastModified.getTime());
return true;
} catch (Throwable e) {
tempFile.delete();
if (monitor != null) {
monitor.failedDownloadFromHost(host.toString(), artifact, e);
}
return false;
}
}
private void endNotifyMonitor(
CacheMonitorRouter monitor, boolean existed, Artifact artifact, File destination) {
if (monitor != null) {
if (existed) {
monitor.updatedLocalCache(artifact.toURL(), destination);
} else {
monitor.addedToLocalCache(artifact.toURL(), destination);
}
}
}