crossreferencemanager.java

java 写的一个新闻发布系统

/* Generated by Together */

package org.jahia.content;

import java.util.*;
import org.jahia.utils.JahiaConsole;

/**
 * This class is the main object cross reference class. Basically it uses a
 * hashtable to group object reference this way :
 *
 * objectref -> set of objectrefs
 *
 * This way we can easily determine for a given object where it is referenced.
 * ObjectRefs may be of any kind that's a subclass of the ObjectKey class.
 * @author Serge Huber
 */

public class CrossReferenceManager {

    private Hashtable crossRefTable;
    private static final String KEY_SEPARATOR = "-";

    private static CrossReferenceManager theObject = null;

    protected CrossReferenceManager() {
        JahiaConsole.println("CrossReferenceManager",
                             "Initializing...");
        crossRefTable = new Hashtable();
    }

    /**
     * Returns a singleton instance of this service
     * Note : this is a synchronized access method so it might affect performance
     * if a lot of threads must access it simultaneously.
     * @returns the singleton instance.
     */
    public static synchronized CrossReferenceManager getInstance()
    {
        if (theObject == null) {
            theObject = new CrossReferenceManager();
        }
        return theObject;
    } // end getInstance

    /**
     * Retrieve a set of object references, basically all the objects that
     * reference the object passed in parameter
     * @param objectKey an ObjectKey type object that identifies the object for
     * which to retrieve the set of references
     * @returns a set of ObjectKey objects that are the objects that reference
     * the object passed in parameter
     */
    public Set getObjectXRefs(ObjectKey objectKey) {
        /*
        JahiaConsole.println("CrossReferenceManager.getObjectXRefs",
                             "Retrieving xrefs for object " + objectKey.getKey() );
        */
        return (Set) crossRefTable.get(objectKey.getKey());
    }

    /**
     * Adds a cross reference between the two objects passed in parameter. The
     * first object key is used as the key in the lookup table.
     * @param objectKey the key for the object to add a cross reference to
     * @param objectXRef another key for the object that references the first
     * object
     */
    public void setObjectXRef(ObjectKey objectKey, ObjectKey objectXRef) {
        /*
        JahiaConsole.println("CrossReferenceManager.setObjectXRef",
                             "Setting xref for object " + objectKey.getKey() +
                             " to " + objectXRef.getKey() + " ..." );
        */
        Set curXRefSet;
        if (!crossRefTable.containsKey(objectKey.getKey())) {
            curXRefSet = new TreeSet(new ObjectKeyComparator());
        } else {
            curXRefSet = (Set) crossRefTable.get(objectKey.getKey());
        }
        if (!curXRefSet.contains(objectXRef)) {
            curXRefSet.add(objectXRef);
        }
        crossRefTable.put(objectKey.getKey(),
                          curXRefSet);
    }

    /**
     * Removes all cross references for an object.
     * @param objectKey the key for the object whose references are to be
     * deleted.
     */
    public void removeObjectXRefs(ObjectKey objectKey) {
        // JahiaConsole.println("CrossReferenceManager.removeObjectXRefs",
        //                      "Removing xrefs for object " + objectKey.getKey());
        crossRefTable.remove(objectKey.getKey());
    }
}