workingmemoryfilelogger.java

jboss规则引擎

package org.drools.audit;

/*
 * Copyright 2005 JBoss Inc
 * 
 * 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.
 */

import java.io.FileNotFoundException;
import java.io.FileWriter;
import java.io.ObjectOutputStream;
import java.util.ArrayList;
import java.util.List;

import org.drools.WorkingMemory;
import org.drools.audit.event.LogEvent;

import com.thoughtworks.xstream.XStream;

/**
 * A logger of events generated by a working memory.
 * It stores its information in a file that can be specified.
 * All the events logged are written to the file when the
 * writeToDisk() method is invoked.  The log will contain all
 * the events logged serialized to XML using XStream.
 * Every time a new logger is created, the old event log will
 * be overwritten.
 * 
 * TODO: make this class more scalable, for example
 *  - logging to several files if log becomes too large
 *  - automatically write updates to file at certain time intervals
 *  - ...
 * 
 * @author <a href="mailto:[e-mail]">Kris Verlaenen </a>
 */
public class WorkingMemoryFileLogger extends WorkingMemoryLogger {

    private final List events            = new ArrayList();
    private String     fileName          = "event";
    private int        maxEventsInMemory = 1000;
    private int        nbOfFile          = 0;

    /**
     * Creates a new WorkingMemoryFileLogger for the given working memory.
     * @param workingMemory
     */
    public WorkingMemoryFileLogger(final WorkingMemory workingMemory) {
        super( workingMemory );
    }

    /**
     * Sets the name of the file the events are logged in.
     * No extensions should be given since .log is automatically appended
     * to the file name.
     * The default is an event.log file in the current working directory.
     * This can be a path relative to the current working directory
     * (e.g. "mydir/subDir/myLogFile"), or an absolute path 
     * (e.g. "C:/myLogFile").
     * 
     * @param fileName The name of the file the events should be logged in.
     */
    public void setFileName(final String fileName) {
        this.fileName = fileName;
    }

    /**
     * All events in the log are written to file.
     * The log is automatically cleared afterwards.
     */
    public void writeToDisk() {
        try {
            final XStream xstream = new XStream();
            final ObjectOutputStream out = xstream.createObjectOutputStream( new FileWriter( this.fileName + (this.nbOfFile == 0 ? ".log" : this.nbOfFile + ".log"),
                                                                                             false ) );
            out.writeObject( this.events );
            out.close();
            this.nbOfFile++;
            clear();
        } catch ( final FileNotFoundException exc ) {
            throw new RuntimeException( "Could not create the log file.  Please make sure that directory that the log file should be placed in does exist." );
        } catch ( final Throwable t ) {
            t.printStackTrace( System.err );
        }
    }

    /**
     * Clears all the events in the log.
     */
    public void clear() {
        this.events.clear();
    }

    /**
     * Sets the maximum number of log events that are allowed in memory.
     * If this number is reached, all events are written to file.
     * The default is 1000.
     * 
     * @param maxEventsInMemory The maximum number of events in memory.
     */
    public void setMaxEventsInMemory(final int maxEventsInMemory) {
        this.maxEventsInMemory = maxEventsInMemory;
    }

    /**
     * @see org.drools.audit.WorkingMemoryLogger
     */
    public void logEventCreated(final LogEvent logEvent) {
        this.events.add( logEvent );
        if ( this.events.size() > this.maxEventsInMemory ) {
            writeToDisk();
        }
    }

    public void finalize() {
        writeToDisk();
    }
}