Handle Stream in Custom URI Resolver for Saxon Parser - function

Question

I have to process an xml against an xslt with result-document that create many xml.
As suggested here:
Catch output stream of xsl result-document
I wrote my personal URI Resolver:
public class CustomOutputURIResolver implements OutputURIResolver{
private File directoryOut;
public CustomOutputURIResolver(File directoryOut) {
super();
this.directoryOut = directoryOut;
}
public void close(Result arg0) throws TransformerException {
}
public Result resolve(String href, String base) throws TransformerException {
FileOutputStream fout = null;
try {
File f = new File(directoryOut.getAbsolutePath() + File.separator + href + File.separator + href + ".xml");
f.getParentFile().mkdirs();
fout = new FileOutputStream(f);
} catch (FileNotFoundException e) {
e.printStackTrace();
}
return new StreamResult(fout);
}
}
that get the output directory and then saves here the files.
But then when I tested it in a junit I had some problems in the clean-up phase, when trying to delete the created files and noticed that the FileOutputStream fout is not well handled.
Trying to solve the problem gave me some thoughts:
First I came out with this idea:
public class CustomOutputURIResolver implements OutputURIResolver{
private File directoryOut;
private FileOutputStream fout
public CustomOutputURIResolver(File directoryOut) {
super();
this.directoryOut = directoryOut;
this.fout = null;
}
public void close(Result arg0) throws TransformerException {
try {
if (null != fout) {
fout.flush();
fout.close();
fout = null;
}
} catch (Exception e) {}
}
public Result resolve(String href, String base) throws TransformerException {
try {
if (null != fout) {
fout.flush();
fout.close();
}
} catch (Exception e) {}
fout = null;
try {
File f = new File(directoryOut.getAbsolutePath() + File.separator + href + File.separator + href + ".xml");
f.getParentFile().mkdirs();
fout = new FileOutputStream(f);
} catch (FileNotFoundException e) {
e.printStackTrace();
}
return new StreamResult(fout);
}
}
So the fileOutputStream is closed anytime another one is opened.
But:
1) I don't like this solution very much
2) what if this function is called in a multithread process? (I'm not very skilled about Saxon parsing, so i really don't know..)
3) Is there a chance to create and handle one FileOutputStream for each resolve ?

Answer 1

The reason close() takes a Result argument is so that you can identify which stream to close. Why not:
public void close(Result arg0) throws TransformerException {
try {
if (arg0 instanceof StreamResult) {
OutputStream os = ((StreamResult)arg0).getOutputStream();
os.flush();
os.close();
}
} catch (Exception e) {}
}
From Saxon-EE 9.5, xsl:result-document executes in a new thread, so it's very important that the OutputURIResolver should be thread-safe. Because of this change, from 9.5 an OutputURIResolver must implement an additional method getInstance() which makes it easier to manage state: if your newInstance() method actually creates a new instance, then there will be one instance of the OutputURIResolver for each result document being processed, and it can hold the output stream and close it when requested.