Mybatis如何通过注解开启使用二级缓存

这篇文章主要介绍了Mybatis基于注解开启使用二级缓存,文中通过示例代码介绍的非常详细，对大家的学习或者工作具有一定的参考学习价值,需要的朋友可以参考下

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"/>
    <!--<!–关闭立即加载，其实不用配置，默认为false–>-->
    <!--<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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