Mybatis基于注解开启使用二级缓存

2023-07-22 11:49:10

　　关于Mybatis的一级缓存和二级缓存的概念以及理解可以参照前面文章的介绍。前文连接：https://www.cnblogs.com/hopeofthevillage/p/11427438.html，上文中二级缓存使用的是xml方式的实现，本文主要是补充一下Mybatis中基于注解的二级缓存的开启使用方法。

　　1.在Mybatis的配置文件中开启二级缓存

<?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>

        <!--开启全局的懒加载-->

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

        <!--&lt;!&ndash;关闭立即加载，其实不用配置，默认为false&ndash;&gt;-->

        <!--<setting name="aggressiveLazyLoading" value="false"/>-->

        <!--开启Mybatis的sql执行相关信息打印-->

        <setting name="logImpl" value="STDOUT_LOGGING" />

        <!--默认是开启的，为了加强记忆，还是手动加上这个配置-->

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

    </settings>

    <typeAliases>

        <typeAlias type="com.example.domain.User" alias="user"/>

        <package name="com.example.domain"/>

    </typeAliases>

    <environments default="test">

        <environment id="test">

            <!--配置事务-->

            <transactionManager type="jdbc"></transactionManager>

            <!--配置连接池-->

            <dataSource type="POOLED">

                <property name="driver" value="com.mysql.jdbc.Driver"/>

                <property name="url" value="jdbc:mysql://localhost:3306/test1"/>

                <property name="username" value="root"/>

                <property name="password" value="123456"/>

            </dataSource>

        </environment>

    </environments>

    <mappers>

        <package name="com.example.dao"/>

    </mappers>

</configuration>

　　开启缓存 <setting name="cacheEnabled" value="true"/>，为了查看Mybatis中查询的日志，添加 <setting name="logImpl" value="STDOUT_LOGGING" />开启日志的配置。

　　2.领域类以及Dao

public class User implements Serializable{

    private Integer userId;

    private String userName;

    private Date userBirthday;

    private String userSex;

    private String userAddress;

    private List<Account> accounts;

   省略get和set方法......

}

import com.example.domain.User;

import org.apache.ibatis.annotations.*;

import org.apache.ibatis.mapping.FetchType;

import java.util.List;

@CacheNamespace(blocking = true)

public interface UserDao {

    /**

     * 查找所有用户

     * @return

     */

    @Select("select * from User")

    @Results(id = "userMap",value = {@Result(id = true,column = "id",property = "userId"),

            @Result(column = "username",property = "userName"),

            @Result(column = "birthday",property = "userBirthday"),

            @Result(column = "sex",property = "userSex"),

            @Result(column = "address",property = "userAddress"),

            @Result(column = "id",property = "accounts",many = @Many(select = "com.example.dao.AccountDao.findAccountByUid",fetchType = FetchType.LAZY))

    })

    List<User> findAll();

    /**

     * 保存用户

     * @param user

     */

    @Insert("insert into user(username,birthday,sex,address) values(#{username},#{birthday},#{sex},#{address})")

    void saveUser(User user);

    /**

     * 更新用户

     * @param user

     */

    @Update("update user set username=#{username},birthday=#{birthday},sex=#{sex},address=#{address} where id=#{id}")

    void updateUser(User user);

    /**

     * 删除用户

     * @param id

     */

    @Delete("delete from user where id=#{id}")

    void  deleteUser(Integer id);

    /**

     * 查询用户根据ID

     * @param id

     * @return

     */

    @Select("select * from user where id=#{id}")

    @ResultMap(value = {"userMap"})

    User findById(Integer id);

    /**

     * 根据用户名称查询用户

     * @param name

     * @return

     */

//    @Select("select * from user where username like #{name}")

    @Select("select * from user where username like '%${value}%'")

    List<User> findByUserName(String name);

    /**

     * 查询用户数量

     * @return

     */

    @Select("select count(*) from user")

    int findTotalUser();

}

　　3.在对应的Dao类上面增加注释以开启二级缓存　

　　@CacheNamespace(blocking = true)

　　4.测试

public class UserCacheTest {

    private InputStream in;

    private SqlSessionFactory sqlSessionFactory;

    @Before

    public void init()throws Exception{

        in = Resources.getResourceAsStream("SqlMapConfig.xml");

        sqlSessionFactory = new SqlSessionFactoryBuilder().build(in);

    }

    @After

    public void destory()throws Exception{

        in.close();

    }

    @Test

    public void testFindById(){

        //第一查询

        SqlSession sqlSession1 = sqlSessionFactory.openSession();

        UserDao userDao1 = sqlSession1.getMapper(UserDao.class);

        User user1 = userDao1.findById(41);

        System.out.println(user1);

        //关闭一级缓存

        sqlSession1.close();

        //第二次查询

        SqlSession sqlSession2 = sqlSessionFactory.openSession();

        UserDao userDao2 = sqlSession2.getMapper(UserDao.class);

        User user2 = userDao2.findById(41);

        System.out.println(user2);

        sqlSession1.close();

        System.out.println(user1 == user2);

    }

}

（1）未开启二级缓存时

（2）开启二级缓存时

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