Java 1.4 singleton containing a mutable field
- by Philippe
Hi,
I'm working on a legacy Java 1.4 project, and I have a factory that instantiates a csv file parser as a singleton.
In my csv file parser, however, I have a HashSet that will store objects created from each line of my CSV file. All that will be used by a web application, and users will be uploading CSV files, possibly concurrently.
Now my question is : what is the best way to prevent my list of objects to be modified by 2 users ?
So far, I'm doing the following :
final class MyParser {
private File csvFile = null;
private static Set myObjects = Collections.synchronizedSet(new HashSet);
public synchronized void setFile(File file) {
this.csvFile = file;
}
public void parse()
FileReader fr = null;
try {
fr = new FileReader(csvFile);
synchronized(myObjects) {
myObjects.clear();
while(...) { // foreach line of my CSV, create a "MyObject"
myObjects.add(new MyObject(...));
}
}
} catch (Exception e) {
//...
}
}
}
Should I leave the lock only on the myObjects Set, or should I declare the whole parse() method as synchronized ?
Also, how should I synchronize - both - the setting of the csvFile and the parsing ? I feel like my actual design is broken because threads could modify the csv file several times while a possibly long parse process is running.
I hope I'm being clear enough, because myself am a bit confused on those multi-synchronization issues.
Thanks ;-)
