expiringcacheentry.java

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/*
 * Copyright 2007 the original author or jdon.com
 *
 * 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.
 *
 */
package com.jdon.jivejdon.manager.throttle;

import java.io.Serializable;

/**
 * A cache entry that expires.
 *
 * We use this class to wrap objects being cached and associate a timestamp
 * and timeout period with them so we can know when they expire.
 */
public class ExpiringCacheEntry implements Serializable {
    
    private Object value;
    private long timeCached = -1;
    private long timeout = 0;
    
    
    public ExpiringCacheEntry(Object value, long timeout) {
        this.value = value;
        
        // make sure that we don't support negative values
        if(timeout > 0) {
            this.timeout = timeout;
        }
        
        this.timeCached = System.currentTimeMillis();
    }
    
    
    public long getTimeCached() {
        return this.timeCached;
    }
    
    
    public long getTimeout() {
        return this.timeout;
    }
    
    
    /**
     * Retrieve the value of this cache entry.
     *
     * If the value has expired then we return null.
     */
    public Object getValue() {
        if(this.hasExpired()) {
            return null;
        } else {
            return this.value;
        }
    }
    
    
    /**
     * Determine if this cache entry has expired.
     */
    public boolean hasExpired() {
        
        long now = System.currentTimeMillis();
        
        return ((this.timeCached + this.timeout) < now);
    }
    
}