10.24

今天学习了使用mybatis通过注解的方式实现对数据库最基本的增删改查

定义了一个Emp的类对象

Emp.java

package com.itheima.mybatisdatabaseexample.pojo;

import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;

import java.time.LocalDate;
import java.time.LocalDateTime;
@Data
@AllArgsConstructor
@NoArgsConstructor
public class Emp {
    private Integer id;
    private String username;
    private String password;
    private String name;
    private short gender;
    private String imag;
    private short job;
    private LocalDate entrydate;
    private Integer deptId;
    private LocalDateTime createTime;
    private LocalDateTime updateTime;

}

定义了一个EmpMapper的接口

EmpMapper.java

package com.itheima.mybatisdatabaseexample.mapper;

import com.itheima.mybatisdatabaseexample.pojo.Emp;
import org.apache.ibatis.annotations.*;

import java.time.LocalDate;
import java.time.LocalDateTime;
import java.time.LocalTime;
import java.util.List;

@Mapper

public interface EmpMapper {
    //删除数据
    @Delete("delete from mybaits.emp where id=#{id}")
    public void delete(Integer id);

    @Options(keyProperty = "id", useGeneratedKeys = true)
    @Insert("insert into emp(username, name, gender, image, job, entrydate, dept_id, create_time, update_time)" +
            " VALUES (#{username},#{name},#{gender},#{imag},#{job},#{entrydate},#{deptId},#{createTime},#{updateTime})")
    public void insert(Emp emp);

    @Update("update  emp set username=#{username},name=#{name},gender=#{gender},image=#{imag},job=#{job},entrydate=#{entrydate},dept_id=#{deptId},update_time=#{updateTime} where id=#{id};")
    public void update(Emp emp);
//@Select("select *  from emp where id=#{id}")
//    public Emp select(Integer id);


//查询完善的方式一：起别名
//@Select("select id, username, password, name, gender, image, job, entrydate, dept_id deptId, create_time createTime, update_time updateTime from emp where id=#{id}")
//public Emp select(Integer id);


//方式二 通过@Result @Results手动注解封装
//    @Results({
//            @Result(property = "deptId",column = "dept_id"),
//            @Result(property = "createTime",column = "create_time"),
//            @Result(property = "updateTime",column = "update_time"),
//    })
//    @Select("select *  from emp where id=#{id}")
//    public Emp select(Integer id);


//    方案三:开启mybatis的驼峰命名自动映射开关

    @Select("select *  from emp where id=#{id}")
    public Emp select(Integer id);
//多条件查询
//    @Select("select * from emp where name like '%张%' " +
//            "and gender=1 and entrydate between'2010-01-01' and '2023-01-01'" +
//            " order by update_time desc ;")
//    public List<Emp>list();

    //    使用字符串拼接
    @Select("select * from emp where name like concat('%','张','%')" +
            "and gender=1 and entrydate between'2010-01-01' and '2023-01-01'" +
            " order by update_time desc ;")
    public List<Emp> list();

//    @Select("select * from emp where name like '%${name}%' " +
//            "and gender=#{gender} and entrydate between#{begin} and #{end}" +
//            " order by update_time desc ;")
//    public List<Emp>list(String name,short gender, LocalDate begin, LocalDate end);
}

同时在测试类中定义函数来实现函数

MybatisDatabaseExampleApplicationTests.java

package com.itheima.mybatisdatabaseexample;

import com.itheima.mybatisdatabaseexample.mapper.EmpMapper;
import com.itheima.mybatisdatabaseexample.pojo.Emp;
import org.apache.ibatis.annotations.*;
import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;

import java.time.LocalDate;
import java.time.LocalDateTime;
import java.util.List;

@SpringBootTest
class MybatisDatabaseExampleApplicationTests {
    @Autowired
    private EmpMapper empMapper;

    @Test
    public void testDelete() {
        empMapper.delete(17);
    }

    @Test
    public void insert() {
        Emp emp = new Emp();
        emp.setUsername("Tom1");
        emp.setName("汤姆1");
        emp.setGender((short) 1);
        emp.setImag("1.jpg");
        emp.setJob((short) 1);
        emp.setEntrydate(LocalDate.now());
        emp.setDeptId(1);
        emp.setCreateTime(LocalDateTime.now());
        emp.setUpdateTime(LocalDateTime.now());
        empMapper.insert(emp);
        System.out.println(emp.getId());
    }

    @Test
    public void update() {
        Emp emp = new Emp();
        emp.setUsername("Tom5");
        emp.setName("汤姆5");
        emp.setGender((short) 1);
        emp.setImag("3.jpg");
        emp.setJob((short) 2);
        emp.setEntrydate(LocalDate.of(2022, 10, 15));
        emp.setDeptId(2);
        emp.setUpdateTime(LocalDateTime.now());
        emp.setId(20);
        empMapper.update(emp);
    }

    @Test
    public void select() {
        Emp emp = empMapper.select(7);
        System.out.println(emp);
    }


    @Test
    public void selectByCondition() {
        List<Emp> empList = empMapper.list();
        System.out.println(empList);
    }
//    @Test
//    public void selectByCondition()
//    {
//List<Emp>empList=empMapper.list("张",(short)1,LocalDate.of(2010,01,01),LocalDate.of(2020,01,01));
//        System.out.println(empList);
//    }
}

当然在application.properties的配置文件中 我们需要配置连接数据库的基本设置

application.properties

#?????
spring.datasource.driver-class-name=com.mysql.cj.jdbc.Driver
#???????url
spring.datasource.url=jdbc:mysql://localhost:3306/mybaits
#?????????
spring.datasource.username=root
#??
spring.datasource.password=123456789
#??mybatis?????????????
mybatis.configuration.log-impl=org.apache.ibatis.logging.stdout.StdOutImpl

#kaiqi tuofengmingming zidongyingshe kaiguan
mybatis.configuration.map-underscore-to-camel-case=true

第一行说明我们需要的连接数据库驱动，同时第二行是要链接的url地址，第三行是连接数据库的地址，第四行是连接数据库的密码，第五行是配置是现在控制台打印出运行与数据库连接的日志信息，第六行是配置出开启驼峰命名自动映射的开关，此开关的作用是可以在搜查元素时，当java代码中的变量名和数据库表中不一致时，且java代码的变量是驼峰命名，数据库中是下划线命名时，自动匹配相应信息。