Examples with CoercionNotFoundException org.apache.tapestry5.commons.util.CoercionNotFoundException used on opensource projects

Example 1 with CoercionNotFoundException

use of org.apache.tapestry5.commons.util.CoercionNotFoundException in project tapestry-5 by apache.

the class TypeCoercerImpl method findOrCreateCoercion.

/**
 * Here's the real meat; we do a search of the space to find coercions, or a system of
 * coercions, that accomplish
 * the desired coercion.
 *
 * There's <strong>TREMENDOUS</strong> room to improve this algorithm. For example, inheritance lists could be
 * cached. Further, there's probably more ways to early prune the search. However, even with dozens or perhaps
 * hundreds of tuples, I suspect the search will still grind to a conclusion quickly.
 *
 * The order of operations should help ensure that the most efficient tuple chain is located. If you think about how
 * tuples are added to the queue, there are two factors: size (the number of steps in the coercion) and
 * "class distance" (that is, number of steps up the inheritance hiearchy). All the appropriate 1 step coercions
 * will be considered first, in class distance order. Along the way, we'll queue up all the 2 step coercions, again
 * in class distance order. By the time we reach some of those, we'll have begun queueing up the 3 step coercions, and
 * so forth, until we run out of input tuples we can use to fabricate multi-step compound coercions, or reach a
 * final response.
 *
 * This does create a good number of short lived temporary objects (the compound tuples), but that's what the GC is
 * really good at.
 *
 * @param sourceType
 * @param targetType
 * @return coercer from sourceType to targetType
 */
@SuppressWarnings("unchecked")
private Coercion findOrCreateCoercion(Class sourceType, Class targetType) {
    if (sourceType == Void.class) {
        return searchForNullCoercion(targetType);
    }
    // Trying to find exact match.
    Optional<CoercionTuple> maybeTuple = getTuples(sourceType, targetType).stream().filter((t) -> sourceType.equals(t.getSourceType()) && targetType.equals(t.getTargetType())).findFirst();
    if (maybeTuple.isPresent()) {
        return maybeTuple.get().getCoercion();
    }
    // These are instance variables because this method may be called concurrently.
    // On a true race, we may go to the work of seeking out and/or fabricating
    // a tuple twice, but it's more likely that different threads are looking
    // for different source/target coercions.
    Set<CoercionTuple.Key> consideredTuples = CollectionFactory.newSet();
    LinkedList<CoercionTuple> queue = CollectionFactory.newLinkedList();
    seedQueue(sourceType, targetType, consideredTuples, queue);
    while (!queue.isEmpty()) {
        CoercionTuple tuple = queue.removeFirst();
        // If the tuple results in a value type that is assignable to the desired target type,
        // we're done! Later, we may add a concept of "cost" (i.e. number of steps) or
        // "quality" (how close is the tuple target type to the desired target type). Cost
        // is currently implicit, as compound tuples are stored deeper in the queue,
        // so simpler coercions will be located earlier.
        Class tupleTargetType = tuple.getTargetType();
        if (targetType.isAssignableFrom(tupleTargetType)) {
            return tuple.getCoercion();
        }
        // So .. this tuple doesn't get us directly to the target type.
        // However, it *may* get us part of the way. Each of these
        // represents a coercion from the source type to an intermediate type.
        // Now we're going to look for conversions from the intermediate type
        // to some other type.
        queueIntermediates(sourceType, targetType, tuple, consideredTuples, queue);
    }
    throw new CoercionNotFoundException(String.format("Could not find a coercion from type %s to type %s.", sourceType.getName(), targetType.getName()), buildCoercionCatalog(), sourceType, targetType);
}