Jedis缓存实现类

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pom.xml导入架包

<!-- 导入jedis架包 --><dependency>  <groupId>redis.clients</groupId>  <artifactId>jedis</artifactId>  <version>2.7.1</version></dependency>

Jedis缓存实现类

package cn.et.mybatis.buff;import java.io.ByteArrayInputStream;import java.io.ByteArrayOutputStream;import java.io.IOException;import java.io.ObjectInputStream;import java.io.ObjectOutputStream;import java.util.Set;import java.util.concurrent.locks.ReadWriteLock;import java.util.concurrent.locks.ReentrantReadWriteLock;import org.apache.commons.pool2.impl.GenericObjectPoolConfig;import org.apache.ibatis.cache.Cache;import redis.clients.jedis.Jedis;import redis.clients.jedis.JedisPool;public class JedisCache implements Cache {/** * 序列化和反序列化的操作类 * @author Administrator * */static class SeqUtils{/** * 对象序列化成字节数组 * @param obj * @return * @throws IOException */public static byte[] ser(Object obj) throws IOException{ByteArrayOutputStream baos=new ByteArrayOutputStream();ObjectOutputStream obos=new ObjectOutputStream(baos);obos.writeObject(obj);return baos.toByteArray();}/** * 反序列化为对象 * @param bt * @return * @throws IOException * @throws ClassNotFoundException */static public Object deSer(byte[] bt) throws IOException, ClassNotFoundException{ByteArrayInputStream bais=new ByteArrayInputStream(bt);ObjectInputStream ois = new ObjectInputStream(bais);return ois.readObject();}}static JedisPool jp = null;private String id;public JedisCache(String id){if(jp==null){try {GenericObjectPoolConfig gopc=new GenericObjectPoolConfig();gopc.setMaxTotal(100);gopc.setMaxIdle(10);jp=new JedisPool(gopc, "localhost");//去数据库连接一下，这样出错就会抛异常Jedis jedis = jp.getResource();jp.returnResourceObject(jedis);} catch (Exception e) {//e.printStackTrace();jp=null;}}this.id=id;}/** * 清空所有的缓存 */public void clear() {Jedis jedis = jp.getResource();jedis.flushAll();jp.returnResourceObject(jedis);}/** * 返回当前的id */public String getId() {return this.id;}/** * maBatis会自动调用该方法，判断返回值是否为null * 如果为空就去数据查 * 不为空就直接返回缓存对象 */public Object getObject(Object key) {//从连接池中获取一条连接Jedis jedis = jp.getResource();try {byte[] bt = jedis.get(SeqUtils.ser(key));if(bt!=null){Object obj = SeqUtils.deSer(bt);//将redis对象回收到连接池中jp.returnResourceObject(jedis);return obj;}} catch (Exception e) {e.printStackTrace();}return null;}/** * non-block io非阻塞式IO * 读写锁 * 同一时间只能有一个线程访问 */public ReadWriteLock getReadWriteLock() {return new ReentrantReadWriteLock();}/** * 用于读取redis中缓存了多少元素 */public int getSize() {Jedis jedis=jp.getResource();Set<String> allElements=jedis.keys("*");return allElements.size();}/** * 第一次查询数据库后mybatis会自动调用该方法将数据写入缓存 */public void putObject(Object key, Object value) {Jedis jedis=jp.getResource();try {jedis.set(SeqUtils.ser(key), SeqUtils.ser(value));//将redis对象回收到连接池中jp.returnResourceObject(jedis);} catch (IOException e) {e.printStackTrace();}}/** * 调用了myBatis flush方法自动清空缓存 * 自动调用removeObject 需要从redis中删除该元素 */public Object removeObject(Object key) {Jedis jedis=jp.getResource();try {jedis.del(SeqUtils.ser(key));//将redis对象回收到连接池中jp.returnResourceObject(jedis);} catch (IOException e) {e.printStackTrace();}return null;}}

emp_mapper.xml

<!--        加上cache标签就开启mybatis的二级缓存了  eviction="LRU"  eviction属性  FIFO 将队列最右端的数据T出内在  为先进先去  LFU  使用次数最少的T出内存   这个在这里不支持  LRU  最近使用次数最少的   -->  <cache  type="cn.et.mybatis.buff.JedisCache"></cache>   <select id="queryEmp2" resultType="cn.et.mybatis.lesson05.buff.Emp">select empno,ename,sal from emp where empno=#{0}  </select>

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