Java tutorial
/* * * Artistic License * * Preamble * * The intent of this document is to state the conditions under which a Package may be copied, such that * the Copyright Holder maintains some semblance of artistic control over the development of the * package, while giving the users of the package the right to use and distribute the Package in a * more-or-less customary fashion, plus the right to make reasonable modifications. * * Definitions: * * "Package" refers to the collection of files distributed by the Copyright Holder, and derivatives * of that collection of files created through textual modification. * * "Standard Version" refers to such a Package if it has not been modified, or has been modified * in accordance with the wishes of the Copyright Holder. * * "Copyright Holder" is whoever is named in the copyright or copyrights for the package. * * "You" is you, if you're thinking about copying or distributing this Package. * * "Reasonable copying fee" is whatever you can justify on the basis of media cost, duplication * charges, time of people involved, and so on. 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THIS PACKAGE IS PROVIDED "AS IS" AND WITHOUT ANY EXPRESS OR IMPLIED * WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF * MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE. * */ package org.chiba.xml.xforms.constraints; import org.apache.commons.jxpath.JXPathContext; import org.apache.commons.jxpath.Pointer; import org.apache.commons.jxpath.ri.Parser; import org.apache.log4j.Category; import org.apache.xerces.dom.NodeImpl; import org.chiba.xml.xforms.Instance; import org.chiba.xml.xforms.LocalValue; import org.chiba.xml.xforms.xpath.PathUtil; import java.util.Enumeration; import java.util.Iterator; import java.util.List; import java.util.Vector; /** * Superclass for Dependency Checking. * * @author This code is based on the ideas of Mikko Honkala from the X-Smiles project. * Although it has been heavily refactored and rewritten to meet our needs. * @version $Id: DependencyGraph.java,v 1.19 2004/12/21 15:35:11 unl Exp $ */ public class DependencyGraph { /** * Logger */ protected static Category LOGGER = Category.getInstance(DependencyGraph.class); /** * holds all vertices for a model */ protected Vector vertices; /** * Creates a new DependencyGraph object. */ public DependencyGraph() { this.vertices = new Vector(); } /** * returns a Vertex of given type that is attached to a given instanceNode * * @param instanceNode the instance data node to check for Vertex * @param property the wanted Model Item Property * @return returns the matching Vertex object or null if not found */ public Vertex getVertex(NodeImpl instanceNode, short property) { Enumeration enumeration = vertices.elements(); while (enumeration.hasMoreElements()) { Vertex v = (Vertex) enumeration.nextElement(); boolean equalNodes = v.instanceNode == instanceNode; boolean equalTypes = v.getVertexType() == property; if (equalNodes && equalTypes) { return v; } } return null; } /** * determines which nodes are referenced by given xpath expression and returns them as nodes. * * @param xpath - the xpath expression under examination * @return a list with nodes referenced in given xpath */ public Vector getXPathRefNodes(JXPathContext relativeContext, String xpath) { ReferenceFinder referenceFinder = new ReferenceFinder(); Parser.parseExpression(xpath, referenceFinder); List pathes = referenceFinder.getLocationPathes(); Vector refNodes = new Vector(); for (int i = 0; i < pathes.size(); i++) { String refPath = pathes.get(i).toString(); Instance instance = (Instance) relativeContext.getParentContext().getContextBean(); JXPathContext context = relativeContext; if (PathUtil.hasInstanceFunction(refPath)) { String instanceId = PathUtil.getInstanceId(instance.getModel(), refPath); // use container for instance lookup to allow cross-model references instance = (Instance) instance.getModel().getContainer().lookup(instanceId); context = instance.getInstanceContext(); } // iterate all referenced nodes Iterator iterator = context.iteratePointers(refPath); while (iterator.hasNext()) { Pointer localPointer = (Pointer) iterator.next(); // Object node = localPointer.getNode(); // if (node instanceof Pointer) { // localPointer = (Pointer) node; // } String realPath = localPointer.asPath(); LocalValue localValue = instance.getModelItem(realPath); if (localValue != null) { // add *existing* reference node refNodes.add(localValue.getNode()); } } } return refNodes; } /** * constructs edges for dependency graph. * * @param from connecting Vertex * @param to connected Vertex */ public void addEdge(Vertex from, Vertex to) { from.addDep(to); if (LOGGER.isDebugEnabled()) { LOGGER.debug("added edge from " + from + " to " + to); } } /** * adds a new vertex to the graph. * If the vertex v already exists in graph: * - if v.bind == null, then update v.bind = bind * This is called by MainDependencyGraph.addBind() */ public Vertex addVertex(JXPathContext relativeContext, NodeImpl instanceNode, String xpathExpression, short property) { Vertex v = this.getVertex(instanceNode, property); if (v != null) { v.wasAlreadyInGraph = true; // set value of pre-built vertex. vertices are pre-built when // they are referenced before their bind is processed if (v.relativeContext == null) { v.relativeContext = relativeContext; v.xpathExpression = xpathExpression; } if (LOGGER.isDebugEnabled()) { LOGGER.debug("found vertex " + v); } return v; } switch (property) { case Vertex.CALCULATE_VERTEX: v = new CalculateVertex(relativeContext, instanceNode, xpathExpression); break; case Vertex.RELEVANT_VERTEX: v = new RelevantVertex(relativeContext, instanceNode, xpathExpression); break; case Vertex.READONLY_VERTEX: v = new ReadonlyVertex(relativeContext, instanceNode, xpathExpression); break; case Vertex.CONSTRAINT_VERTEX: v = new ConstraintVertex(relativeContext, instanceNode, xpathExpression); break; case Vertex.REQUIRED_VERTEX: v = new RequiredVertex(relativeContext, instanceNode, xpathExpression); break; } if (LOGGER.isDebugEnabled()) { LOGGER.debug("built vertex " + v); } vertices.addElement(v); return v; } /** * adds a Vertex to the pool hold by this object. Will add no duplicates to the collection. * * @param v the Vertex to add */ private void addVertex(Vertex v) { if (!vertices.contains(v)) { vertices.addElement(v); } } /** * print the list of vertices */ public void printGraph() { Enumeration enumeration = vertices.elements(); while (enumeration.hasMoreElements()) { Vertex v = (Vertex) enumeration.nextElement(); if (LOGGER.isDebugEnabled()) { LOGGER.debug("Next vertex:"); } v.print(0); } } /** * recalculates this graph. */ public void recalculate() { if (LOGGER.isDebugEnabled()) { LOGGER.debug("starting recalculation ..."); } // remove non zero vertices this.removeNonZeroVertices(); while (this.vertices.size() > 0) { // remove a vertex v from Z Vertex v = (Vertex) this.vertices.firstElement(); this.removeVertex(v); v.compute(); Enumeration enumeration = v.depList.elements(); while (enumeration.hasMoreElements()) { Vertex w = (Vertex) enumeration.nextElement(); w.inDegree--; if (w.inDegree == 0) { this.addVertex(w); } } } if (LOGGER.isDebugEnabled()) { LOGGER.debug("... recalculation finished"); } } private void removeNonZeroVertices() { Vector nonzeros = new Vector(); Enumeration enumeration = vertices.elements(); while (enumeration.hasMoreElements()) { Vertex v = (Vertex) enumeration.nextElement(); if (v.inDegree > 0) { nonzeros.addElement(v); } } enumeration = nonzeros.elements(); while (enumeration.hasMoreElements()) { Vertex v = (Vertex) enumeration.nextElement(); this.removeVertex(v); } } /** * removes a Vertex from the collection. * * @param v the Vertex to remove */ protected void removeVertex(Vertex v) { this.vertices.removeElement(v); } } //end of class