简介
简单接收Mybatis中二级缓存的使用示例
概览
主要部分如下：
- 引入Maven依赖
- SpringBoot配置文件配置、建库与初始化SQL语句
- 实体类与Mapper编写
- 测试
Maven依赖
完整依赖大致如下：
xml
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<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
......
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>8.0.11</version>
</dependency>
<dependency>
<groupId>org.mybatis.spring.boot</groupId>
<artifactId>mybatis-spring-boot-starter</artifactId>
<version>2.2.0</version>
</dependency>
<dependency>
<groupId>org.projectlombok</groupId>
<artifactId>lombok</artifactId>
<optional>true</optional>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<scope>test</scope>
</dependency>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>4.13</version>
<scope>test</scope>
</dependency>
</dependencies>
......
</project>
SpringBoot配置文件配置、建库与初始化SQL语句
配置文件如下：
yaml
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spring:
datasource:
url: jdbc:mysql://localhost:3306/test?serverTimezone=UTC&useUnicode=true&characterEncoding=utf-8&allowPublicKeyRetrieval=true&useSSL=false
username: root
password: root
driver-class-name: com.mysql.cj.jdbc.Driver
sql:
init:
schema-locations: classpath:mybatis/schema-mysql.sql
data-locations: classpath:mybatis/data-mysql.sql
mybatis:
configuration:
cache-enabled: true
mapper-locations: classpath:mybatis/mapper/*.xml
logging.level.com.example.cache.mapper: debug
建库DDL：
mysql
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DROP TABLE IF EXISTS user;
CREATE TABLE user
(
id BIGINT(20) NOT NULL COMMENT '主键ID',
name VARCHAR(30) NULL DEFAULT NULL COMMENT '姓名',
age INT(11) NULL DEFAULT NULL COMMENT '年龄',
email VARCHAR(50) NULL DEFAULT NULL COMMENT '邮箱',
PRIMARY KEY (id)
);
数据初始化DDL：
mysql
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DELETE FROM `user`;
INSERT INTO `user` (id, name, age, email) VALUES
(1, 'Jone', 18, 'test1@baomidou.com'),
(2, 'Jack', 20, 'test2@baomidou.com'),
(3, 'Tom', 28, 'test3@baomidou.com'),
(4, 'Sandy', 21, 'test4@baomidou.com'),
(5, 'Billie', 24, 'test5@baomidou.com');
实体类与Mapper编写
User实体类：
java
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import lombok.Data;
import java.io.Serializable;
@Data
public class User implements Serializable {
private Long id;
private String name;
private Integer age;
private String email;
}
UserMapper.java
java
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import com.example.cache.entity.User;
import org.springframework.stereotype.Repository;
import java.util.List;
@Repository
public interface UserMapper {
List<User> select();
}
UserMapper.xml
xml
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<?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="com.example.cache.mapper.UserMapper"><cache/>
<select id="select" resultType="com.example.cache.entity.User">
select * from `user`;
</select>
</mapper>
测试
测试代码如下：
java
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import com.example.cache.entity.User;
import com.example.cache.mapper.UserMapper;
import lombok.extern.slf4j.Slf4j;
import org.junit.jupiter.api.Assertions;
import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;
import java.util.List;
@SpringBootTest
public class UserTest {
@Autowired
private UserMapper userMapper;
@Test
public void testSelectOneCache() {
List<User> users = userMapper.select();
Assertions.assertEquals(5, users.size());
users.forEach(System.out::println);
users = userMapper.select();
Assertions.assertEquals(5, users.size());
users.forEach(System.out::println);
}
}
输出如下：
shell
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2021-06-08 22:38:48.925 DEBUG 7296 --- [ main] c.e.cache.mapper.UserMapper.select : ==> Preparing: select * from `user`;
2021-06-08 22:38:48.950 DEBUG 7296 --- [ main] c.e.cache.mapper.UserMapper.select : ==> Parameters:
2021-06-08 22:38:48.979 DEBUG 7296 --- [ main] c.e.cache.mapper.UserMapper.select : <== Total: 5
User(id=1, name=Jone, age=18, email=test1@baomidou.com)
User(id=2, name=Jack, age=20, email=test2@baomidou.com)
User(id=3, name=Tom, age=28, email=test3@baomidou.com)
User(id=4, name=Sandy, age=21, email=test4@baomidou.com)
User(id=5, name=Billie, age=24, email=test5@baomidou.com)
2021-06-08 22:38:48.995 WARN 7296 --- [ main] o.apache.ibatis.io.SerialFilterChecker : As you are using functionality that deserializes object streams, it is recommended to define the JEP-290 serial filter. Please refer to https://docs.oracle.com/pls/topic/lookup?ctx=javase15&id=GUID-8296D8E8-2B93-4B9A-856E-0A65AF9B8C66
2021-06-08 22:38:48.997 DEBUG 7296 --- [ main] com.example.cache.mapper.UserMapper : Cache Hit Ratio [com.example.cache.mapper.UserMapper]: 0.5
User(id=1, name=Jone, age=18, email=test1@baomidou.com)
User(id=2, name=Jack, age=20, email=test2@baomidou.com)
User(id=3, name=Tom, age=28, email=test3@baomidou.com)
User(id=4, name=Sandy, age=21, email=test4@baomidou.com)
User(id=5, name=Billie, age=24, email=test5@baomidou.com)
可以看到第二次查询没有走SQL查询，直接从Cache中取得了结果
总结
一篇简单的Mybatis二级缓存的示例
从中可以看到，SpringBoot Mybatis是默认开启二级缓存的，其他更多的使用，如缓存失效等，后面再探索
