element.java

EasyDBO v0.4 是一个非常适合中小型软件数据库开发的数据持久层框架

package com.easyjf.cache;

import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.Serializable;

import org.apache.log4j.Logger;

public class Element implements Serializable, Cloneable {	
    static final long serialVersionUID = -7401070179721710788L;
    private final static Logger logger = Logger.getLogger(Element.class);
    /**
     * 元素的key，值及版本
     */
    private final Object key; 
    private Object value;   
    private long version;
   /**
    *访问情况
    */
    private long creationTime;
    private long lastAccessTime;
    private long nextToLastAccessTime;
    private long hitCount;//命中数

    public Element(Object key, Object value, long version) {
        this.key = key;
        this.value = value;
        this.version = version;
        creationTime = System.currentTimeMillis();
        hitCount = 0;
    }
   
    public Element(Object key, Object value) {
        this(key, value, 1L);
    }
   
 
    public boolean equals(Object obj) {
        Element element = (Element)obj;
        if (key.equals(element.getKey())) {
            return true;
        }
        return false;
    }

    public void resetAccessStatistics() {
        lastAccessTime = 0;
        nextToLastAccessTime = 0;
        hitCount = 0;
    }

    public void updateAccessStatistics() {
        nextToLastAccessTime = lastAccessTime;
        lastAccessTime = System.currentTimeMillis();
        hitCount++;
    }

    public String toString() {
        StringBuffer sb = new StringBuffer();
        sb.append("[ key = ").append(key)
                .append(", value=").append(value)
                .append(", version=").append(version)
                .append(", hitCount=").append(hitCount)
                .append(", CreationTime = ").append(this.getCreationTime())
                .append(", LastAccessTime = ").append(this.getLastAccessTime())
                .append(" ]");

        return sb.toString();
    }

      public Object clone() throws CloneNotSupportedException {
        Element element = new Element(deepCopy(key), deepCopy(value), version);
        element.creationTime = creationTime;
        element.lastAccessTime = lastAccessTime;
        element.nextToLastAccessTime = nextToLastAccessTime;
        element.hitCount = hitCount;
        return element;
    }

    private Serializable deepCopy(Object oldValue) {
        Serializable newValue = null;
        ByteArrayOutputStream bout = new ByteArrayOutputStream();
        ObjectOutputStream oos = null;
        ObjectInputStream ois = null;
        try {
            oos = new ObjectOutputStream(bout);
            oos.writeObject(oldValue);
            ByteArrayInputStream bin = new ByteArrayInputStream(bout.toByteArray());
            ois = new ObjectInputStream(bin);
            newValue = (Serializable) ois.readObject();
        } catch (IOException e) {
           logger.error("Error cloning Element with key " + key
                    + " during serialization and deserialization of value");
        } catch (ClassNotFoundException e) {
            logger.error("Error cloning Element with key " + key
                    + " during serialization and deserialization of value");
        } finally {
            try {
                oos.close();
                ois.close();
            } catch (IOException e) {
                logger.error("Error closing Stream");
            }
        }
        return newValue;
    }

    public long getSerializedSize() {
        long size = 0;
        ByteArrayOutputStream bout = new ByteArrayOutputStream();
        ObjectOutputStream oos = null;
        try {
            oos = new ObjectOutputStream(bout);
            oos.writeObject(this);
            size = bout.size();
            return size;
        } catch (IOException e) {
           logger.error("Error measuring element size for element with key " + key);
        } finally {
            try {
                oos.close();
            } catch (IOException e) {
                logger.error("Error closing ObjectOutputStream");
            }
        }

        return size;
    }
    

    public Object getKey() {
        return key;
    }

    public Object getValue() {
        return value;
    }
    public int hashCode() {
        return key.hashCode();
    }
    
    public void setVersion(long version) {
        this.version = version;
    }

    public long getCreationTime() {
        return creationTime;
    }

    public void setCreateTime() {
        creationTime = System.currentTimeMillis();
    }

    public long getVersion() {
        return version;
    }
    public long getLastAccessTime() {
        return lastAccessTime;
    }

    long getNextToLastAccessTime() {
        return nextToLastAccessTime;
    }

    public long getHitCount() {
        return hitCount;
    }
}