Mybatis源码阅读之LRU(LruCache )

 

 

 

package org.apache.ibatis.cache.decorators;

 

import org.apache.ibatis.cache.Cache;

 

import java.util.LinkedHashMap;

import java.util.Map;

import java.util.concurrent.locks.ReadWriteLock;

 

/**

 * Lru (first in, first out) cache decorator

 */

public class LruCache implements Cache {

 

  private final Cache delegate;

  private Map<Object, Object> keyMap;

  private Object eldestKey;

 

  public LruCache(Cache delegate) {

    this.delegate = delegate;

    setSize(1024);

  }

 

  public String getId() {

    return delegate.getId();

  }

 

  public int getSize() {

    return delegate.getSize();

  }

 

  public void setSize(final int size) {

    keyMap = new LinkedHashMap<Object, Object>(size, .75F, true) {

      private static final long serialVersionUID = 4267176411845948333L;

 

      protected boolean removeEldestEntry(Map.Entry<Object, Object> eldest) {

        boolean tooBig = size() > size;

        if (tooBig) {

          eldestKey = eldest.getKey();

        }

        return tooBig;

      }

    };

  }

 

  public void putObject(Object key, Object value) {

    delegate.putObject(key, value);

    cycleKeyList(key);

  }

 

  public Object getObject(Object key) {

    keyMap.get(key); //touch

    return delegate.getObject(key);

 

  }

 

  public Object removeObject(Object key) {

    return delegate.removeObject(key);

  }

 

  public void clear() {

    delegate.clear();

    keyMap.clear();

  }

 

  public ReadWriteLock getReadWriteLock() {

    return delegate.getReadWriteLock();

  }

 

  private void cycleKeyList(Object key) {

    keyMap.put(key, key);

    if (eldestKey != null) {

      delegate.removeObject(eldestKey);

      eldestKey = null;

    }

  }

 

}