simplecacheimpl.java

来自「JAVA Servlet2.3外文书籍源码」· Java 代码 · 共 94 行

package cache;

import java.util.HashMap;
import java.util.Iterator;

public class SimpleCacheImpl implements ICache {
    
    private String name = "";
    private int size = 100;
    private int currentSize = 0;
    private HashMap objectMap;

    /** @link aggregation */
    /*#ICacheable lnkICacheable;*/
    
    public SimpleCacheImpl() {
        objectMap = new HashMap();        
    }
    
    public String getName() {
        return name;
    }
    
    public void setName(String name) {
        this.name = name;
    }
    
    public int getSize() {
        return size;
    }
    
    public void setSize(int size) {
        this.size = size;
    }
    
    public ICacheable getCacheable(Object identifier) {
        
        synchronized(this) {
            ICacheable cacheable = (ICacheable)objectMap.get(identifier);
            if(cacheable != null)
                cacheable.setLastAccessedTime(System.currentTimeMillis());
            return cacheable;
        }
        
    }
    
    public void expire() {
        
        synchronized(this) {
            Iterator it = objectMap.keySet().iterator();
            while(it.hasNext()) {
                ICacheable current = (ICacheable)objectMap.get(it.next());
                if(current.getExpiryTime() != 0 && current.getExpiryTime() <= System.currentTimeMillis()) {
                    currentSize--;
                    objectMap.remove(current.getIdentifier());
                }
            }
        }
        
    }
    
    public void addCacheable(ICacheable cacheable) {
        
        synchronized(this) {
            
            if(objectMap.containsKey(cacheable.getIdentifier()))
                return;
            
            if(currentSize == size) {
                Iterator it = objectMap.keySet().iterator();
                long time = System.currentTimeMillis();
                ICacheable lastAccessed = null;
                while(it.hasNext()) {
                    ICacheable current = (ICacheable)objectMap.get(it.next());
                    if(current.getLastAccessedTime() < time) {
                        time = current.getLastAccessedTime();
                        lastAccessed = current;
                    }
                }
                if(lastAccessed != null) {
                    currentSize--;
                    objectMap.remove(lastAccessed.getIdentifier());
                }
                
            }
            cacheable.setLastAccessedTime(System.currentTimeMillis());
            objectMap.put(cacheable.getIdentifier(), cacheable);
            currentSize++;
        }
        
    }
    
}