MyBatis二级缓存配置

正如大多数持久层框架一样,MyBatis 同样提供了一级缓存二级缓存的支持

Mybatis二级缓存是SessionFactory,如果两次查询基于同一个SessionFactory,那么就从二级缓存中取数据,而不用到数据库里去取了。

  1. 一级缓存: 基于PerpetualCache 的 HashMap本地缓存,其存储作用域为 Session,当 Session flush 或 close 之后,该Session中的所有 Cache 就将清空

  2. 二级缓存与一级缓存其机制相同,默认也是采用 PerpetualCache,HashMap存储,不同在于其存储作用域为 Mapper(Namespace),并且可自定义存储源,如 Ehcache。

启动二级缓存:

  1.mybatis-config.xml添加

    <setting name="cacheEnabled" value="true"/>

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE configuration
PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
"http://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>
    <settings>  
        <setting name="logImpl" value="STDOUT_LOGGING"/> 
        <setting name="cacheEnabled" value="true"/><!-- 二级缓存 -->
    </settings> 
    <typeAliases>
      <package name="pojo"/>
    </typeAliases> 
    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.jdbc.Driver"/>
                <property name="url" value="jdbc:mysql://localhost:3306/lol?characterEncoding=UTF-8"/>
                <property name="username" value="root"/>
                <property name="password" value="root"/>
            </dataSource>
        </environment>
    </environments>
    <mappers>
        <mapper resource="pojo/Product.xml"/>
    </mappers>
</configuration>

  2.在Product.xml(数据库关系映射)中增加 <cache/>

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE mapper
    PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
    "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
 
    <mapper namespace="pojo">
        <cache/>
        <insert id="addProduct" parameterType="Product" >
            insert into product (name, price) values (#{name}, #{price})    
        </insert>
        <select id="listProduct" resultType="Product">
            select * from  product     
        </select>
         <delete id="deleteProduct" parameterType="Product" >
            delete from product where id= #{id}   
        </delete>
        <select id="getProduct" parameterType="_int" resultType="Product">
            select * from product where id=#{id}
        </select>
        <select id="listProductByIdAndName" resultType="Product">
            <bind name="likename" value="'%' + name + '%'" />
               select * from product 
               <where>
                   <if test="name!=null">
                   and name like #{likename}
                   <if test="price!=null">
                   and price > #{price}
                   </if>
               </if> 
               </where>
               
        </select>
    </mapper>

  3.序列化Product.java(pojo类)

     通常来说,二级缓存的机制里会有一个: 当缓存的个数达到某个数量的时候,把缓存对象保存在硬盘上。 如果要把对象保存在硬盘上,就必须实现序列化接口。

     序列化相关知识:http://blog.csdn.net/wangloveall/article/details/7992448/  

package pojo;

import java.io.Serializable;

public class Product implements Serializable{
 
    private int id;
    private String name;
    private float price;
    public int getId() {
        return id;
    }
    public void setId(int id) {
        this.id = id;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public float getPrice() {
        return price;
    }
    public void setPrice(float price) {
        this.price = price;
    }
}

  4.测试类

package controller;

import java.io.IOException;
import java.io.InputStream;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;

import pojo.Product;

public class TestMybatis {
    public static void main(String [] args) throws IOException{
        String resource = "mybatis-config.xml";
        InputStream inputStream = Resources.getResourceAsStream(resource);
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        SqlSession session = sqlSessionFactory.openSession();
        
        Product p = session.selectOne("getProduct", 1);
        session.commit();
        session.close();
        
        SqlSession session1 = sqlSessionFactory.openSession();//二级缓存测试
        Product p2 = session1.selectOne("getProduct", 1);
        session1.commit();
        session1.close();
    }
}

  5.结果

 

  

posted @ 2017-08-23 15:20  Junsept  阅读(1689)  评论(0编辑  收藏  举报