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'rapiddweller Common' is an open source Java library
forked from Databene Commons by Volker Bergmann.
It provides extensions to the Java core library by utility classes, abstract concepts
and concrete implementations.
/*
* Copyright (C) 2004-2015 Volker Bergmann ([email protected]).
* All rights reserved.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
* http://www.apache.org/licenses/LICENSE-2.0
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.rapiddweller.common.depend;
import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import static com.rapiddweller.common.depend.NodeState.FORCEABLE;
import static com.rapiddweller.common.depend.NodeState.INITIALIZABLE;
import static com.rapiddweller.common.depend.NodeState.INITIALIZED;
import static com.rapiddweller.common.depend.NodeState.PARTIALLY_INITIALIZABLE;
/**
* Orders objects by dependency.
*
* @param the type of the objects to process
* @author Volker Bergmann
* @since 0.3.04
*/
@SuppressWarnings("static-method")
public class DependencyModel> {
private static final Logger LOGGER = LogManager.getLogger(DependencyModel.class);
private final Map> nodeMappings;
/**
* Instantiates a new Dependency model.
*/
public DependencyModel() {
this.nodeMappings = new HashMap<>();
}
/**
* Add node.
*
* @param object the object
*/
public void addNode(E object) {
nodeMappings.put(object, new Node<>(object));
}
/**
* Dependency ordered objects list.
*
* @param acceptingCycles the accepting cycles
* @return the list
*/
public List dependencyOrderedObjects(boolean acceptingCycles) {
// set up dependencies
for (Node node : nodeMappings.values()) {
E subject = node.getSubject();
for (int i = 0; i < subject.countProviders(); i++) {
E provider = subject.getProvider(i);
Node providerNode = nodeMappings.get(provider);
if (providerNode == null) {
throw new IllegalStateException("Node is not part of model: " + provider);
}
providerNode.addClient(node);
node.addProvider(providerNode, subject.requiresProvider(i));
}
}
// set up lists for processing
List> heads = new ArrayList<>();
List> tails = new ArrayList<>();
List> pending = new ArrayList<>(nodeMappings.size());
List> orderedNodes = new ArrayList<>(nodeMappings.size());
List> incompletes = new ArrayList<>();
try {
// determine types and extract islands
for (Node node : nodeMappings.values()) {
if (node.hasForeignClients()) {
if (node.hasForeignProviders()) {
pending.add(node);
} else {
node.initialize();
heads.add(node);
}
} else {
if (node.hasForeignProviders()) {
tails.add(node);
} else {
node.initialize();
orderedNodes.add(node);
}
}
}
// extract heads
orderedNodes.addAll(heads);
// sort remaining nodes
while (pending.size() > 0) {
boolean found = extractNodes(pending, INITIALIZABLE, orderedNodes, null);
if (!found) {
found = extractNodes(pending, PARTIALLY_INITIALIZABLE, orderedNodes, incompletes);
}
if (!found) {
if (acceptingCycles) {
// force one node
Node node = findForceable(pending);
LOGGER.debug("forcing " + node);
pending.remove(node);
node.force();
orderedNodes.add(node);
incompletes.add(node);
} else {
throw new CyclicDependencyException("Cyclic dependency in " + pending);
}
}
postProcessNodes(incompletes);
}
if (incompletes.size() > 0) {
throw new IllegalStateException("Incomplete nodes left: " + incompletes);
}
// extract tails
for (Node tail : tails) {
tail.initialize();
}
orderedNodes.addAll(tails);
// done
if (LOGGER.isDebugEnabled()) {
LOGGER.debug("ordered to " + orderedNodes);
}
// map result
List result = new ArrayList<>(orderedNodes.size());
for (Node node : orderedNodes) {
E subject = node.getSubject();
if (node.getState() != INITIALIZED) {
throw new IllegalStateException("Node '" + subject
+ "' is expected to be in INITIALIZED state, found: " + node.getState());
}
result.add(subject);
}
return result;
} catch (RuntimeException e) {
if (!(e instanceof CyclicDependencyException)) {
logState(pending);
}
throw e;
}
}
private void postProcessNodes(List> nodes) {
LOGGER.debug("post processing nodes: {}", nodes);
Iterator> iterator = nodes.iterator();
while (iterator.hasNext()) {
Node node = iterator.next();
switch (node.getState()) {
case PARTIALLY_INITIALIZABLE:
case INITIALIZED:
LOGGER.debug("Initializing {} partially", node);
node.initializePartially();
break;
case INITIALIZABLE:
LOGGER.debug("Initializing {}", node);
node.initialize();
iterator.remove();
break;
default:
break;
}
}
}
private boolean extractNodes(List> source, NodeState requiredState, List> target, List> incompletes) {
LOGGER.debug("extracting nodes from {}", source);
Iterator> iterator;
boolean found = false;
iterator = source.iterator();
while (iterator.hasNext()) {
Node node = iterator.next();
if (node.getState() == requiredState) {
iterator.remove();
switch (requiredState) {
case INITIALIZABLE:
LOGGER.debug("Initializing {}", node);
node.initialize();
break;
case PARTIALLY_INITIALIZABLE:
LOGGER.debug("Initializing {} partially", node);
node.initializePartially();
if (incompletes != null) {
incompletes.add(node);
}
break;
default:
throw new IllegalArgumentException("state not supported: " + requiredState);
}
if (target != null) {
target.add(node);
}
found = true;
}
}
return found;
}
private void logState(List> intermediates) {
LOGGER.error(intermediates.size() + " unresolved intermediates on DependencyModel error: ");
for (Node node : intermediates) {
LOGGER.error(node.toString());
}
}
private Node findForceable(List> candidates) {
for (Node candidate : candidates) {
if (candidate.getState() == FORCEABLE) {
return candidate;
}
}
return candidates.get(0);
}
/*
private Node breakCycle(List> remainingNodes, List> availableNodes, boolean hard) {
for (Node node : remainingNodes) {
if (available(node))
logger.warn("Cyclic dependency in " + tmpList + ". Breaking cycle by extracting " + node);
result.add(node);
tmpList.remove(0);
}
}
private Node findAvailableNode(List> tmpList, List> availableNodes) {
for (Node node : tmpList)
if (available(node, availableNodes))
return node;
return null;
}
private boolean available(Node candidate, List> availableNodes) {
for (Node usedNode : candidate.getProviders())
if (!availableNodes.contains(usedNode))
return false;
return true;
}
*/
}