mybatis学习笔记(16)-mybatis整合ehcache

mybatis学习笔记(16)-mybatis整合ehcache

标签： mybatis

ehcache是一个分布式缓存框架

分布缓存

我们系统为了提高系统并发，性能、一般对系统进行分布式部署（集群部署方式）

不使用分布缓存，缓存的数据在各各服务单独存储，不方便系统开发。所以要使用分布式缓存对缓存数据进行集中管理。

mybatis无法实现分布式缓存，需要和其它分布式缓存框架进行整合。

整合方法(掌握)

mybatis提供了一个cache接口，如果要实现自己的缓存逻辑，实现cache接口开发即可。

mybatis和ehcache整合，mybatis和ehcache整合包中提供了一个cache接口的实现类。

package org.apache.ibatis.cache;

import java.util.concurrent.locks.ReadWriteLock;

/** * SPI for cache providers. * * One instance of cache will be created for each namespace. * * The cache implementation must have a constructor that receives the cache id as an String parameter. * * MyBatis will pass the namespace as id to the constructor. * * <pre> * public MyCache(final String id) { * if (id == null) { * throw new IllegalArgumentException("Cache instances require an ID"); * } * this.id = id; * initialize(); * } * </pre> * * @author Clinton Begin */

public interface Cache {

  /** * @return The identifier of this cache */
  String getId();

  /** * @param key Can be any object but usually it is a {@link CacheKey} * @param value The result of a select. */
  void putObject(Object key, Object value);

  /** * @param key The key * @return The object stored in the cache. */
  Object getObject(Object key);

  /** * Optional. It is not called by the core. * * @param key The key * @return The object that was removed */
  Object removeObject(Object key);

  /** * Clears this cache instance */  
  void clear();

  /** * Optional. This method is not called by the core. * * @return The number of elements stored in the cache (not its capacity). */
  int getSize();

  /** * Optional. As of 3.2.6 this method is no longer called by the core. * * Any locking needed by the cache must be provided internally by the cache provider. * * @return A ReadWriteLock */
  ReadWriteLock getReadWriteLock();

}

mybatis默认实现cache类是：

package org.apache.ibatis.cache.impl;

import java.util.HashMap;
import java.util.Map;
import java.util.concurrent.locks.ReadWriteLock;

import org.apache.ibatis.cache.Cache;
import org.apache.ibatis.cache.CacheException;

/** * @author Clinton Begin */
public class PerpetualCache implements Cache {

  private String id;

  private Map<Object, Object> cache = new HashMap<Object, Object>();

  public PerpetualCache(String id) {
    this.id = id;
  }

  public String getId() {
    return id;
  }

  public int getSize() {
    return cache.size();
  }

  public void putObject(Object key, Object value) {
    cache.put(key, value);
  }

  public Object getObject(Object key) {
    return cache.get(key);
  }

  public Object removeObject(Object key) {
    return cache.remove(key);
  }

  public void clear() {
    cache.clear();
  }

  public ReadWriteLock getReadWriteLock() {
    return null;
  }

  public boolean equals(Object o) {
    if (getId() == null) throw new CacheException("Cache instances require an ID.");
    if (this == o) return true;
    if (!(o instanceof Cache)) return false;

    Cache otherCache = (Cache) o;
    return getId().equals(otherCache.getId());
  }

  public int hashCode() {
    if (getId() == null) throw new CacheException("Cache instances require an ID.");
    return getId().hashCode();
  }

}

整合ehcache

• 加入ehcache包
  
  • ehcache-core-2.6.5.jar
  • mybatis-ehcache-1.0.2.jar

配置mapper中cache中的type为ehcache对cache接口的实现类型

 <!-- 开启本mapper的namespace下的二级缓存 type：指定cache接口的实现类的类型，mybatis默认使用PerpetualCache 要和ehcache整合，需要配置type为ehcache实现cache接口的类型 <cache /> -->
    <cache type="org.mybatis.caches.ehcache.EhcacheCache"/>

加入ehcache的配置文件

在classpath下配置ehcache.xml

<ehcache xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="../config/ehcache.xsd">
    <diskStore path="F:\develop\ehcache" />
    <defaultCache maxElementsInMemory="1000" maxElementsOnDisk="10000000" eternal="false" overflowToDisk="false" timeToIdleSeconds="120" timeToLiveSeconds="120" diskExpiryThreadIntervalSeconds="120" memoryStoreEvictionPolicy="LRU">
    </defaultCache>
</ehcache>

作者@brianway更多文章：个人网站 | CSDN | oschina