Web后端开发-Mybatis

Mybatis入门

快速入门

public class User {private Integer id;private String name;private Short age;private Short gender;private String phone;public User() {}public User(Integer id, String name, Short age, Short gender, String phone) {this.id = id;this.name = name;this.age = age;this.gender = gender;this.phone = phone;}public Integer getId() {return id;}public void setId(Integer id) {this.id = id;}public String getName() {return name;}public void setName(String name) {this.name = name;}public Short getAge() {return age;}public void setAge(Short age) {this.age = age;}public Short getGender() {return gender;}public void setGender(Short gender) {this.gender = gender;}public String getPhone() {return phone;}public void setPhone(String phone) {this.phone = phone;}@Overridepublic String toString() {return "User{" +"id=" + id +", name='" + name + '\'' +", age=" + age +", gender=" + gender +", phone='" + phone + '\'' +'}';}
}

JDBC介绍

#配置数据库的连接信息 - 四要素
#驱动类名称
spring.datasource.driver-class-name=com.mysql.cj.jdbc.Driver
#数据库连接的url
spring.datasource.url=jdbc:mysql://localhost:3306/mybatis
#连接数据库的用户名
spring.datasource.username=root
#连接数据库的密码
spring.datasource.password=...

package com.itheima.mapper;import com.itheima.pojo.User;
import org.apache.ibatis.annotations.Mapper;
import org.apache.ibatis.annotations.Select;import java.util.List;@Mapper //在运行时,会自动生成该接口的实现类对象(代理对象), 并且将该对象交给IOC容器管理
public interface UserMapper {//查询全部用户信息@Select("select * from user")public List<User> list();}

package com.itheima;import com.itheima.mapper.UserMapper;
import com.itheima.pojo.User;
import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;import java.sql.*;
import java.util.ArrayList;
import java.util.List;@SpringBootTest //springboot整合单元测试的注解
class SpringbootMybatisQuickstartApplicationTests {@Autowiredprivate UserMapper userMapper;@Testpublic void testListUser(){List<User> userList = userMapper.list();userList.stream().forEach(user -> {System.out.println(user);});}
}

JDBC介绍

package com.itheima;import com.itheima.mapper.UserMapper;
import com.itheima.pojo.User;
import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;import java.sql.*;
import java.util.ArrayList;
import java.util.List;@SpringBootTest //springboot整合单元测试的注解
class SpringbootMybatisQuickstartApplicationTests {@Autowiredprivate UserMapper userMapper;@Testpublic void testListUser(){List<User> userList = userMapper.list();userList.stream().forEach(user -> {System.out.println(user);});}@Testpublic void testJdbc() throws Exception {//1. 注册驱动Class.forName("com.mysql.cj.jdbc.Driver");//2. 获取连接对象String url = "jdbc:mysql://localhost:3306/mybatis";String username = "root";String password = "...";Connection connection = DriverManager.getConnection(url, username, password);//3. 获取执行SQL的对象Statement,执行SQL,返回结果String sql = "select * from user";Statement statement = connection.createStatement();ResultSet resultSet = statement.executeQuery(sql);//4. 封装结果数据List<User> userList = new ArrayList<>();while (resultSet.next()){int id = resultSet.getInt("id");String name = resultSet.getString("name");short age = resultSet.getShort("age");short gender = resultSet.getShort("gender");String phone = resultSet.getString("phone");User user = new User(id,name,age,gender,phone);userList.add(user);}//5. 释放资源statement.close();connection.close();//5. 释放资源statement.close();connection.close();userList.stream().forEach(user -> {System.out.println(user);});}
}

数据库连接池

#配置数据库的连接信息 - 四要素
#驱动类名称
spring.datasource.driver-class-name=com.mysql.cj.jdbc.Driver
#数据库连接的url
spring.datasource.url=jdbc:mysql://localhost:3306/mybatis
#连接数据库的用户名
spring.datasource.username=root
#连接数据库的密码
spring.datasource.password=...

用druid的话，datasource.druid中druid可省略！也就是要从默认切换Druid，只需添加Druid依赖

lombok

package com.itheima.pojo;import lombok.*;//@Getter
//@Setter
//@ToString
//@EqualsAndHashCode@Data
@NoArgsConstructor //无参构造
@AllArgsConstructor //全参构造
public class User {private Integer id;private String name;private Short age;private Short gender;private String phone;/*public User() {}public User(Integer id, String name, Short age, Short gender, String phone) {this.id = id;this.name = name;this.age = age;this.gender = gender;this.phone = phone;}public Integer getId() {return id;}public void setId(Integer id) {this.id = id;}public String getName() {return name;}public void setName(String name) {this.name = name;}public Short getAge() {return age;}public void setAge(Short age) {this.age = age;}public Short getGender() {return gender;}public void setGender(Short gender) {this.gender = gender;}public String getPhone() {return phone;}public void setPhone(String phone) {this.phone = phone;}@Overridepublic String toString() {return "User{" +"id=" + id +", name='" + name + '\'' +", age=" + age +", gender=" + gender +", phone='" + phone + '\'' +'}';}*/
}

Mybatis基础增删改查

准备

删除

    //根据ID删除数据@Delete("delete from emp where id = #{id}")public void delete(Integer id);//public int delete(Integer id);

    //根据ID删除@Testpublic void testDelete(){//int delete = empMapper.delete(16);//System.out.println(delete);empMapper.delete(16);}

插入

#指定mybatis输出日志的位置，输出控制台
mybatis.configuration.log-impl=org.apache.ibatis.logging.stdout.StdOutImpl

新增

    //新增员工@Insert("insert into emp(username, name, gender, image, job, entrydate, dept_id, create_time, update_time)" +" values (#{username},#{name},#{gender},#{image},#{job},#{entrydate},#{deptId},#{createTime},#{updateTime})")public void insert(Emp emp);

 //新增员工@Testpublic void testInsert(){//构造员工对象Emp emp = new Emp();emp.setUsername("Tom3");emp.setName("汤姆3");emp.setImage("1.jpg");emp.setGender((short)1);emp.setJob((short)1);emp.setEntrydate(LocalDate.of(2000,1,1));emp.setCreateTime(LocalDateTime.now());emp.setUpdateTime(LocalDateTime.now());emp.setDeptId(1);//执行新增员工信息操作empMapper.insert(emp);}

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

        System.out.println(emp.getId());

更新

    //更新员工@Update("update emp set username = #{username}, name = #{name}, gender = #{gender}, image = #{image}," +" job = #{job}, entrydate = #{entrydate}, dept_id = #{deptId},update_time = #{updateTime} where id = #{id}")public void update(Emp emp);

    //更新员工@Testpublic void testUpdate(){//构造员工对象Emp emp = new Emp();emp.setId(18);emp.setUsername("Tom1");emp.setName("汤姆1");emp.setImage("1.jpg");emp.setGender((short)1);emp.setJob((short)1);emp.setEntrydate(LocalDate.of(2000,1,1));emp.setUpdateTime(LocalDateTime.now());emp.setDeptId(1);//执行更新员工操作empMapper.update(emp);}

查询

#开启mybatis的驼峰命名自动映射开关
mybatis.configuration.map-underscore-to-camel-case=true

  //方案三: 开启mybatis的驼峰命名自动映射开关 --- a_cloumn ------> aColumn//根据ID查询员工@Select("select * from emp where id = #{id}")public Emp getById(Integer id);//方案一: 给字段起别名, 让别名与实体类属性一致//@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 getById(Integer id);//方案二: 通过@Results, @Result注解手动映射封装//@Results({//        @Result(column = "dept_id", property = "deptId"),//        @Result(column = "create_time", property = "createTime"),//        @Result(column = "update_time", property = "updateTime")//})//@Select("select * from emp where id = #{id}")//public Emp getById(Integer id);

  //更新员工@Testpublic void testUpdate(){//构造员工对象Emp emp = new Emp();emp.setId(18);emp.setUsername("Tom1");emp.setName("汤姆1");emp.setImage("1.jpg");emp.setGender((short)1);emp.setJob((short)1);emp.setEntrydate(LocalDate.of(2000,1,1));emp.setUpdateTime(LocalDateTime.now());emp.setDeptId(1);//执行更新员工操作empMapper.update(emp);}

    //条件查询员工//方式一@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);

    //方式二@Select("select * from emp where name like concat('%',#{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);

XML映射文件

    //动态条件查询public List<Emp> list(String name, Short gender, LocalDate begin , LocalDate end);

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapperPUBLIC "-//mybatis.org//DTD Mapper 3.0//EN""http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.itheima.mapper.EmpMapper"><select id="list" resultType="com.itheima.pojo.Emp">select *from empwhere name like concat('%', #{name}, '%')and gender = #{gender}and entrydate between #{begin} and #{end}order by update_time desc</select></mapper>

Mybatis动态SQL

< if >

    <!--resultType: 单条记录封装的类型--><select id="list" resultType="com.itheima.pojo.Emp">select *from emp<where><if test="name != null">and name like concat('%', #{name}, '%')</if><if test="gender != null">and gender = #{gender}</if><if test="begin != null and end != null">and entrydate between #{begin} and #{end}</if></where>order by update_time desc</select>
</mapper>

    //动态更新员工public void update2(Emp emp);

            <!-- 动态更新员工--><update id="update2">update emp<set><if test="username != null">username = #{username},</if><if test="name != null">name = #{name},</if><if test="gender != null">gender = #{gender},</if><if test="image != null">image = #{image},</if><if test="job != null">job = #{job},</if><if test="entrydate != null">entrydate = #{entrydate},</if><if test="deptId != null">dept_id = #{deptId},</if><if test="updateTime != null">update_time = #{updateTime}</if></set>where id = #{id}</update>

  //动态更新员工 - 更新ID为18的员工 username 更新为 Tom111, name更新为 汤姆111, gender更新为2@Testpublic void testUpdate2(){//构造员工对象Emp emp = new Emp();emp.setId(19);emp.setUsername("Tom222333");
//        emp.setName("汤姆222");
//        emp.setGender((short)1);
//        emp.setUpdateTime(LocalDateTime.now());//执行更新员工操作empMapper.update2(emp);}

< foreach >

    //批量删除员工public void deleteByIds(List<Integer> ids);

  <!--批量删除员工 (18,19,20)--><!--collection: 遍历的集合item: 遍历出来的元素separator: 分隔符open: 遍历开始前拼接的SQL片段close: 遍历结束后拼接的SQL片段--><delete id="deleteByIds">delete  from emp where id in<foreach collection="ids" item="id" separator="," open="(" close=")">#{id}</foreach></delete>

    //批量删除员工 - 13,14,15@Testpublic void testDeleteByIds(){List<Integer> ids = Arrays.asList(13, 14, 15);empMapper.deleteByIds(ids);}

< sql >< include >

    <sql id="commonSelect">select id, username, password, name, gender, image, job, entrydate, dept_id, create_time, update_timefrom emp</sql>

   <!--resultType: 单条记录封装的类型--><select id="list" resultType="com.itheima.pojo.Emp"><include refid="commonSelect"/><where><if test="name != null">name like concat('%', #{name}, '%')</if><if test="gender != null">and gender = #{gender}</if><if test="begin != null and end != null">and entrydate between #{begin} and #{end}</if></where>order by update_time desc</select>