ibatis 源码分享1---FifoCacheController

最近在学习Ibatis 源码,看到FifoCacheController在项目很有用途分享大家

package com.ibatis.sqlmap.engine.cache.fifo;

import java.util.Collections;
import java.util.HashMap;
import java.util.LinkedList;
import java.util.List;
import java.util.Map;
import java.util.Properties;

import com.ibatis.sqlmap.engine.cache.CacheController;
import com.ibatis.sqlmap.engine.cache.CacheModel;

/**
 * FIFO (first in, first out) cache controller implementation
 */
public class FifoCacheController implements CacheController {

  private int cacheSize;
  private Map cache;
  private List keyList;

  /**
   * Default constructor
   */
  public FifoCacheController() {
    this.cacheSize = 100;
    
     //用Map放key value 可以用ConcurrentHashMap优化性能
     this.cache = Collections.synchronizedMap(new HashMap());
     //用LinkedList放key
     this.keyList = Collections.synchronizedList(new LinkedList());
  }

  public int getCacheSize() {
    return cacheSize;
  }

  public void setCacheSize(int cacheSize) {
    this.cacheSize = cacheSize;
  }

  /**
   * Configures the cache
   *
   * @param props Optionally can contain properties [reference-type=WEAK|SOFT|STRONG]
   */
  public void setProperties(Properties props) {
    String size = props.getProperty("cache-size");
    if (size == null) {
      size = props.getProperty("size");
    }
    if (size != null) {
      cacheSize = Integer.parseInt(size);
    }
  }

  /**
   * Add an object to the cache
   *
   * @param cacheModel The cacheModel
   * @param key        The key of the object to be cached
   * @param value      The object to be cached
   */
  public void putObject(CacheModel cacheModel, Object key, Object value) {
    cache.put(key, value);
    keyList.add(key);
    //如果超过大小就删除头部元素
    if (keyList.size() > cacheSize) {
      try {
        Object oldestKey = keyList.remove(0);
        cache.remove(oldestKey);
      } catch (IndexOutOfBoundsException e) {
        //ignore
      }
    }
  }

  /**
   * Get an object out of the cache.
   *
   * @param cacheModel The cache model
   * @param key        The key of the object to be returned
   * @return The cached object (or null)
   */
  public Object getObject(CacheModel cacheModel, Object key) {
    return cache.get(key);
  }

  public Object removeObject(CacheModel cacheModel, Object key) {
    keyList.remove(key);
    return cache.remove(key);
  }

  /**
   * Flushes the cache.
   *
   * @param cacheModel The cache model
   */
  public void flush(CacheModel cacheModel) {
    cache.clear();
    keyList.clear();
  }

}