dbtreewalker.java

来自「Jive是基于JSP/JAVA技术构架的一个大型BBS论坛系统,这是Jive论坛」· Java 代码 · 共 217 行

/**
 * $RCSfile: DbTreeWalker.java,v $
 * $Revision: 1.5 $
 * $Date: 2002/05/13 19:41:23 $
 *
 * Copyright (C) 1999-2002 CoolServlets, Inc. All rights reserved.
 *
 * This software is the proprietary information of CoolServlets, Inc.
 * Use is subject to license terms.
 */

package com.jivesoftware.forum.database;

import java.sql.*;
import java.util.Iterator;
import java.io.*;

import com.jivesoftware.forum.*;
import com.jivesoftware.util.*;

/**
 * Database implementation of the TreeWalker interface. It caches the tree
 * structure in memory for fastest access.<p>
 *
 * One important caveat is the following: we assumes that no child message
 * will have a creation date that is earlier in time than its parent message.
 * The assumption lets us make some big optimization gains and is safe as long
 * as all the data is created in Jive Forums. The only possible problem is if
 * data is imported from other forum apps that don't follow this behavior (not
 * very likely).
 *
 * @author Matt Tucker
 */
public class DbTreeWalker implements TreeWalker, Serializable {

    /** DATABASE QUERIES **/
    private static final String MESSAGE_COUNT =
        "SELECT count(*) FROM jiveMessage WHERE threadID=?";
    private static final String GET_MESSAGES =
        "SELECT messageID, parentMessageID, creationDate FROM jiveMessage " +
        "WHERE threadID=? AND parentMessageID IS NOT NULL " +
        "ORDER BY creationDate ASC";

    private long threadID;
    private LongTree tree;
    private transient DbForumFactory factory;

    /**
     * Creates a new TreeWalker instance.
     */
    public DbTreeWalker(DbForumThread thread) {
        this.threadID = thread.getID();
        factory = DbForumFactory.getInstance();

        // Now, build the rest of the tree.
        Connection con = null;
        PreparedStatement pstmt = null;
        try {
            con = ConnectionManager.getConnection();
            // First, get the count.
            pstmt = con.prepareStatement(MESSAGE_COUNT);
            pstmt.setLong(1, thread.getID());
            ResultSet rs = pstmt.executeQuery();
            rs.next();
            int numMessages = rs.getInt(1);
            pstmt.close();
            // Create the tree, set the root.
            tree = new LongTree(thread.getRootMessage().getID(), numMessages);

            // Now, load the actual results.
            pstmt = con.prepareStatement(GET_MESSAGES);
            pstmt.setLong(1, thread.getID());
            rs = pstmt.executeQuery();
            int count = 1;
            // Keep reading items into the tree until we run out of db
            // results, or we hit the max number of elements that we defined
            // for the tree. Only very rarely should the count change while
            // reading in the tree.
            while(rs.next() && count < numMessages) {
                count++;
                long messageID = rs.getLong(1);
                long parentMessageID = rs.getLong(2);
                tree.addChild(parentMessageID, messageID);
            }
        }
        catch (SQLException sqle) {
            sqle.printStackTrace();
        }
        finally {
            try {  pstmt.close();   }
            catch (Exception e) { e.printStackTrace(); }
            try {  con.close();   }
            catch (Exception e) { e.printStackTrace(); }
        }
    }

    private void readObject(java.io.ObjectInputStream in)
         throws IOException, ClassNotFoundException
    {
        in.defaultReadObject();
        factory = DbForumFactory.getInstance();
    }

    //FROM THE TREEWALKER INTERFACE//

    public ForumMessage getRoot() {
        ForumThread thread = null;
        try {
            thread = factory.cacheManager.getForumThread(threadID);
        }
        catch (Exception e) {
            return null;
        }
        return thread.getRootMessage();
    }

    public int getChildCount(ForumMessage parent) {
        return tree.getChildCount(parent.getID());
    }

    public ForumMessage getParent(ForumMessage message)
            throws ForumMessageNotFoundException
    {
        long parentID = tree.getParent(message.getID());
        if (parentID == -1) {
            throw new ForumMessageNotFoundException();
        }
        else {
            ForumThread thread = null;
            try {
                thread = factory.cacheManager.getForumThread(threadID);
            }
            catch (Exception e) {
                throw new ForumMessageNotFoundException();
            }
            return thread.getMessage(parentID);
        }
    }

    public ForumMessage getChild(ForumMessage message, int index)
            throws ForumMessageNotFoundException
    {
        long childID = tree.getChild(message.getID(), index);
        if (childID == -1) {
            throw new ForumMessageNotFoundException();
        }
        else {
            ForumThread thread = null;
            try {
                thread = factory.cacheManager.getForumThread(threadID);
            }
            catch (Exception e) {
                throw new ForumMessageNotFoundException();
            }
            return thread.getMessage(childID);
        }
    }

    public Iterator children(ForumMessage parent) {
        long [] children = tree.getChildren(parent.getID());
        return new DatabaseObjectIterator(JiveGlobals.MESSAGE, children,
                parent.getForumThread());
    }

    public Iterator recursiveChildren(ForumMessage parent) {
        long [] messages = tree.getRecursiveChildren(parent.getID());
        return new DatabaseObjectIterator(JiveGlobals.MESSAGE, messages,
                parent.getForumThread());
    }

    public int getMessageDepth(ForumMessage message) {
        int depth = tree.getDepth(message.getID());
        if (depth == -1) {
            throw new IllegalArgumentException("Message " + message.getID() +
                    " does not belong to this thread.");
        }
        return depth;
    }

    public int getRecursiveChildCount(ForumMessage parent) {
        //Call the recursive method.
        return getRecursiveChildCount(parent.getID());
    }

    public int getIndexOfChild(ForumMessage parent, ForumMessage child) {
        return tree.getIndexOfChild(parent.getID(), child.getID());
    }

    public boolean isLeaf(ForumMessage message) {
        return tree.isLeaf(message.getID());
    }

    //OTHER METHODS//

    public int getSize() {
        int size = 0;
        size += CacheSizes.sizeOfObject();
        size += tree.getCachedSize();
        size += CacheSizes.sizeOfLong();
        size += CacheSizes.sizeOfLong();
        size += CacheSizes.sizeOfObject();
        return size;
    }

    private int getRecursiveChildCount(long parentID) {
        int numChildren = 0;
        int num = tree.getChildCount(parentID);
        numChildren += num;
        for (int i=0; i<num; i++) {
            long childID = tree.getChild(parentID, i);
            if (childID != -1) {
                numChildren += getRecursiveChildCount(childID);
            }
        }
        return numChildren;
    }
}