querycacheupdatetask.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 135 行

/**
 * $RCSfile: QueryCacheUpdateTask.java,v $
 * $Revision: 1.2 $
 * $Date: 2002/07/12 00:35:59 $
 *
 * Copyright 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 com.jivesoftware.forum.*;
import com.jivesoftware.util.*;

import java.sql.*;

/**
 * A task to reload a cache entry from the database and then move it from the
 * short-term query cache and into the long-term cache.
 */
public class QueryCacheUpdateTask implements Runnable {

    private QueryCacheKey key;

    /**
     * Creates a new cache entry update task.
     *
     * @param key the key for the cache entry to be updated.
     */
    public QueryCacheUpdateTask(QueryCacheKey key) {
        this.key = key;
    }

    public void run() {
        DbForumFactory factory = DbForumFactory.getInstance();
        try {
            int blockID = key.getBlockID();
            // Determine the block size.
            int blockSize = 0;
            switch (key.getObjectType()) {
                case JiveGlobals.FORUM_CATEGORY:
                    blockSize = DbForumCategory.BLOCK_SIZE;
                    break;
                case JiveGlobals.FORUM:
                    blockSize = DbForum.BLOCK_SIZE;
                    break;
                case JiveGlobals.THREAD:
                    blockSize = DbForum.BLOCK_SIZE;
            }

            Object value = null;
            Connection con = null;
            Statement stmt = null;
            try {
                con = ConnectionManager.getConnection();
                // If this is not a count query, load a block of results from the db.
                if (key.blockID != -1) {
                    stmt = ConnectionManager.createScrollableStatement(con);
                    LongList objectList = new LongList(blockSize);

                    // Set the maximum number of rows to end at the end of this block.
                    ConnectionManager.setMaxRows(stmt, blockSize * (blockID+1));
                    ResultSet rs = stmt.executeQuery(key.getSql());
                    // Grab BLOCK_SIZE rows at a time.
                    ConnectionManager.setFetchSize(rs, blockSize);
                    // Position the cursor right before the first row that we're insterested in.
                    int blockStart = blockSize * blockID;
                    ConnectionManager.scrollResultSet(rs, blockStart);
                    // Keep reading results until the result set is exhausted or
                    // we come to the end of the block.
                    int count = 0;
                    while (rs.next() && count < blockSize) {
                        objectList.add(rs.getLong(1));
                        count++;
                    }
                    value = objectList.toArray();
                }
                // Otherwise, this is a count query.
                else {
                    stmt = con.createStatement();
                    ResultSet rs = stmt.executeQuery(key.getSql());
                    rs.next();
                    value = new Integer(rs.getInt(1));
                }
            }
            catch( SQLException sqle ) {
                sqle.printStackTrace();
            }
            finally {
                try {  stmt.close(); }
                catch (Exception e) { e.printStackTrace(); }
                try {  con.close();   }
                catch (Exception e) { e.printStackTrace(); }
            }

            if (value != null) {
                // Add the value to long-term cache.
                factory.cacheManager.queryCache.put(key, value);
                // Add the query key to the object.
                switch (key.getObjectType()) {
                    case JiveGlobals.FORUM_CATEGORY:
                        DbForumCategory category = null;
                        try {
                            category = factory.cacheManager.getForumCategory(key.getObjectID());
                            category.addQueryKey(key);
                        }
                        catch (Exception e) { }
                        break;
                    case JiveGlobals.FORUM:
                         DbForum forum = null;
                         try {
                             forum = factory.cacheManager.getForum(key.getObjectID());
                             forum.addQueryKey(key);
                         }
                         catch (Exception e) { }
                         break;
                    case JiveGlobals.THREAD:
                        DbForumThread thread = null;
                        try {
                            thread = factory.cacheManager.getForumThread(key.getObjectID());
                            thread.addQueryKey(key);
                        }
                        catch (Exception e) { }
                }
            }
        }
        finally {
            // Always remove the cache entry from short-term cache.
            factory.cacheManager.shortTermQueryCache.remove(key);
        }
    }
}