第六天1/4

通过Mybatis操作数据库

Mybatis

Mybatis同样也是一款优秀的持久层框架，前身是iBatis
Mybatis与JPA最大的区别是SQL需要写（有工具辅助生成）

适用情况

整个数据库的操作比较简单用JPA
因为这样不用去关心SQL与映射相关的东西

如果DBA对SQL与映射有把控的要求，例如说每条SQL都需要审核，添加一些hint这样的东西时，
或者SQL比较复杂，存在join等复杂的关联
就需要选择Mybatis

大厂一般都选择Mybatis

Spring中使用Mybatis

Mybatis Spring Adapter 以及Mybatis-spring-boot-starter

在application.properties文件中的配置

mybatis.mapper-locations = classpath*:mapper/**/*.xml
mybatis.type-aliases-package = 类型别名的包名
mybatis.type-handlers-package = TypeHandler扫描包名
mybatis.configuration.map-underscore-to-camel-case = true

@MapperScan 配置扫描位置
@Mapper 定义接口
映射的定义—— XML 与注解（两种定义映射的方式，支持混用）

代码及运行结果

CoffeeMapper

package geektime.spring.data.mybatisdemo.mapper;

import geektime.spring.data.mybatisdemo.model.Coffee;
import org.apache.ibatis.annotations.Insert;
import org.apache.ibatis.annotations.Mapper;
import org.apache.ibatis.annotations.Options;
import org.apache.ibatis.annotations.Param;
import org.apache.ibatis.annotations.Result;
import org.apache.ibatis.annotations.Results;
import org.apache.ibatis.annotations.Select;

@Mapper
public interface CoffeeMapper {
    
    
    @Insert("insert into t_coffee (name, price, create_time, update_time)"
            + "values (#{name}, #{price}, now(), now())")
    @Options(useGeneratedKeys = true)
    int save(Coffee coffee);

    @Select("select * from t_coffee where id = #{id}")
    @Results({
    
    
            @Result(id = true, column = "id", property = "id"),
            @Result(column = "create_time", property = "createTime"),
            // map-underscore-to-camel-case = true 可以实现一样的效果
            // @Result(column = "update_time", property = "updateTime"),
    })
    Coffee findById(@Param("id") Long id);
}

MybatisDemoApplication

package geektime.spring.data.mybatisdemo;

import geektime.spring.data.mybatisdemo.mapper.CoffeeMapper;
import geektime.spring.data.mybatisdemo.model.Coffee;
import lombok.extern.slf4j.Slf4j;
import org.joda.money.CurrencyUnit;
import org.joda.money.Money;
import org.mybatis.spring.annotation.MapperScan;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.ApplicationArguments;
import org.springframework.boot.ApplicationRunner;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
@Slf4j
@MapperScan("geektime.spring.data.mybatisdemo.mapper")
public class MybatisDemoApplication implements ApplicationRunner {
    
    
	@Autowired
	private CoffeeMapper coffeeMapper;

	public static void main(String[] args) {
    
    
		SpringApplication.run(MybatisDemoApplication.class, args);
	}

	@Override
	public void run(ApplicationArguments args) throws Exception {
    
    
		Coffee c = Coffee.builder().name("espresso")
				.price(Money.of(CurrencyUnit.of("CNY"), 20.0)).build();
		int count = coffeeMapper.save(c);
		log.info("Save {} Coffee: {}", count, c);

		c = Coffee.builder().name("latte")
				.price(Money.of(CurrencyUnit.of("CNY"), 25.0)).build();
		count = coffeeMapper.save(c);
		log.info("Save {} Coffee: {}", count, c);

		c = coffeeMapper.findById(c.getId());
		log.info("Find Coffee: {}", c);
	}
}

运行输出：
在这里插入图片描述

Mybatis操作数据库-Spring入门学习笔记11

学习笔记@玩转Spring全家桶