package com.vitco.util.misc;
import java.io.Closeable;
import java.util.LinkedList;
import java.util.List;
public abstract class AutoFileCloser {
// the core action code that the implementer wants to run
protected abstract void doWork() throws Throwable;
// track a list of closeable thingies to close when finished
private final List<Closeable> closeables_ = new LinkedList<Closeable>();
// give the implementer a way to track things to close
// assumes this is called in order for nested closeables,
// inner-most to outer-most
protected final <T extends Closeable> T autoClose(T closeable) {
closeables_.add(0, closeable);
return closeable;
}
public AutoFileCloser() {
// a variable to track a "meaningful" exception, in case
// a close() throws an exception
Throwable pending = null;
try {
doWork(); // do the real work
} catch (Throwable throwable) {
pending = throwable;
} finally {
// close the watched streams
for (Closeable closeable : closeables_) {
if (closeable != null) {
try {
closeable.close();
} catch (Throwable throwable) {
if (pending == null) {
pending = throwable;
}
}
}
}
// if we had a pending exception, rethrow it
// this is necessary b/c the close can throw an
// exception, which would remove the pending
// status of any exception thrown in the try block
if (pending != null) {
if (pending instanceof RuntimeException) {
//noinspection ThrowFromFinallyBlock
throw (RuntimeException) pending;
} else {
//noinspection ThrowFromFinallyBlock
throw new RuntimeException(pending);
}
}
}
}
}