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;
    }

    @Override
    public 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 {

    @Autowired
    private UserMapper userMapper;

    @Test
    public 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 {

    @Autowired
    private UserMapper userMapper;

    @Test
    public void testListUser(){
        List<User> userList = userMapper.list();
        userList.stream().forEach(user -> {
            System.out.println(user);
        });
    }

    @Test
    public 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;
    }

    @Override
    public 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
    @Test
    public 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
    @Test
    public 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
    @Test
    public 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
    @Test
    public 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 mapper
        PUBLIC "-//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 emp
        where 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
    @Test
    public 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
    @Test
    public 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_time
    from 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>