【Mybatis】FIFO缓冲实现

• Cache 接口定义
• FIFOCache 实现类

FIFO (first in, first out) 即“先进先出”缓冲淘汰算法。

Cache 接口定义

public interface Cache {

  /**
   * 缓冲 ID
   */
  String getId();

  /**
   * 存储数据
   */
  void putObject(Object key, Object value);

  /**
   * 获取数据
   */
  Object getObject(Object key);

  /**
   * 删除数据
   */
  Object removeObject(Object key);

  /**
   * 清空缓冲
   */
  void clear();

  /**
   * 获取缓冲大小
   */
  int getSize();
  
  ReadWriteLock getReadWriteLock();
}

FIFOCache 实现类

FIFOCache 实现 Cache 接口

package org.apache.ibatis.cache.decorators;

import java.util.Deque;
import java.util.LinkedList;
import java.util.concurrent.locks.ReadWriteLock;
import org.apache.ibatis.cache.Cache;

/**
 * FIFO (first in, first out) cache decorator
 */
public class FifoCache implements Cache {

  private final Cache delegate;
  private final Deque<Object> keyList;
  private int size;

  public FifoCache(Cache delegate) {
    this.delegate = delegate;
    this.keyList = new LinkedList<Object>();
    this.size = 1024;
  }

  @Override
  public String getId() {
    return delegate.getId();
  }

  @Override
  public int getSize() {
    return delegate.getSize();
  }

  public void setSize(int size) {
    this.size = size;
  }

  @Override
  public void putObject(Object key, Object value) {
    cycleKeyList(key);
    delegate.putObject(key, value);
  }

  @Override
  public Object getObject(Object key) {
    return delegate.getObject(key);
  }

  @Override
  public Object removeObject(Object key) {
    return delegate.removeObject(key);
  }

  @Override
  public void clear() {
    delegate.clear();
    keyList.clear();
  }

  @Override
  public ReadWriteLock getReadWriteLock() {
    return null;
  }

  private void cycleKeyList(Object key) {
    keyList.addLast(key);
    if (keyList.size() > size) {
      Object oldestKey = keyList.removeFirst();
      delegate.removeObject(oldestKey);
    }
  }
}