timedcache.java

不管是测试驱动开发或者是其它的开发模式

/*  Copyright (c) 2000-2004 jMock.org
 */
package org.jmock.examples.timedcache;

import java.util.HashMap;


public class TimedCache
{
    private ObjectLoader loader;
    private Clock clock;
    private ReloadPolicy reloadPolicy;
    private HashMap cachedValues = new HashMap();

    private class TimestampedValue
    {
        public final Object value;
        public final Timestamp loadTime;

        public TimestampedValue( final Object value, final Timestamp timestamp ) {
            this.value = value;
            this.loadTime = timestamp;
        }
    }


    public TimedCache( ObjectLoader loader, Clock clock, ReloadPolicy reloadPolicy ) {
        this.loader = loader;
        this.clock = clock;
        this.reloadPolicy = reloadPolicy;
    }

    public Object lookup( Object theKey ) {
        TimestampedValue found = (TimestampedValue)cachedValues.get(theKey);

        if (found == null || reloadPolicy.shouldReload(found.loadTime, clock.getCurrentTime())) {
            found = loadObject(theKey);
        }
        return found.value;
    }

    private TimestampedValue loadObject( Object key ) {
        Object value = loader.load(key);
        TimestampedValue timestampedValue = new TimestampedValue(value, clock.getCurrentTime());

        cachedValues.put(key, timestampedValue);

        return timestampedValue;
    }

    public void putValue( Object key, Object value, Timestamp loadTime ) {
        cachedValues.put(key, new TimestampedValue(value, loadTime));

    }
}