net.java.truecommons.shed.PriorityExceptionBuilder Maven / Gradle / Ivy
/*
* Copyright (C) 2005-2012 Schlichtherle IT Services.
* All rights reserved. Use is subject to license terms.
*/
package net.java.truecommons.shed;
import java.util.*;
import javax.annotation.CheckForNull;
import javax.annotation.concurrent.NotThreadSafe;
/**
* Assembles an {@link Exception} from one or more input exceptions by
* {@linkplain Exception#addSuppressed(Throwable) suppressing} all but the
* first input exception with the highest priority.
* The priority of the exceptions is determined by the {@link Comparator}
* provided to the constructor.
*
* @param the type of the input and assembled (output) exceptions.
* @author Christian Schlichtherle
*/
@NotThreadSafe
public class PriorityExceptionBuilder
extends AbstractExceptionBuilder {
private final Comparator comparator;
private final List exceptions;
/**
* Constructs a new priority exception builder.
* This builder will use the first input exception as its initial assembly.
* Whenever a new input exception gets added, the given comparator will get
* used to determine if the new input exception shall get suppressed by the
* current assembly or shall suppress the current assembly and take its
* place.
* The comparator will get called like this:
* {@code comparator.compare(input, assembly)} where {@code input}
* is the input exception to add and {@code assembly} is the current
* assembly.
*
* @param comparator the comparator used for prioritizing the exceptions in
* the assembly.
*/
public PriorityExceptionBuilder(final Comparator comparator) {
if (null == (this.comparator = comparator))
throw new NullPointerException();
exceptions = new LinkedList<>();
}
@Override
protected final X update(final X input, final @CheckForNull X assembly) {
exceptions.add(input);
return null == assembly
? input
: comparator.compare(input, assembly) > 0 ? input : assembly;
}
@Override
protected final X post(final X selection) {
for ( final Iterator i = exceptions.iterator();
i.hasNext();
i.remove()) {
final X exception = i.next();
if (selection != exception) selection.addSuppressed(exception);
}
assert exceptions.isEmpty();
return selection;
}
}