创建测试用的数据库

CREATE DATABASE `mybatis_plus` /*!40100 DEFAULT CHARACTER SET utf8mb4 */; use `mybatis_plus`;
CREATE TABLE `user` (
`id` bigint(20) NOT NULL COMMENT '主键ID',
`name` varchar(30) DEFAULT NULL COMMENT '姓名 ',
`age` int(11) DEFAULT NULL COMMENT '年龄 ',
`email` varchar(50) DEFAULT NULL COMMENT '邮箱 ',
PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

向数据库插入数据

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');

pom文件中引入依赖

<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<scope>test</scope>
</dependency>
<dependency>
<groupId>com.baomidou</groupId>
<artifactId>mybatis-plus-boot-starter</artifactId>
<version>3.5.1</version>
</dependency>
<dependency>
<groupId>org.projectlombok</groupId>
<artifactId>lombok</artifactId>
<optional>true</optional>
</dependency>
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<scope>runtime</scope>
</dependency>
</dependencies>

idea中安装lombok插件

配置application.yml

具体的数据库名，用户名，密码更换为自己的

spring:
# 配置数据源信息
datasource:
# 配置数据源类型
type: com.zaxxer.hikari.HikariDataSource
# 配置连接数据库信息
driver-class-name: com.mysql.cj.jdbc.Driver
url: jdbc:mysql://localhost:3306/mybatis_plus?characterEncoding=utf- 8&useSSL=false
username: root
password: 123456

设置在启动类设置mapper扫描的包

@MapperScan("zoo.mapper")
@SpringBootApplication(exclude = {DataSourceAutoConfiguration.class})
public class SpringDemo2Application {
    public static void main(String[] args) {
        SpringApplication.run(SpringDemo2Application.class, args);
    }
}

添加实体类

• 这里实体类的主键也就是id必须为Long类型的。

@Data //lombok注解
public class User {

private Long id;
private String name;
private Integer age;
private String email;

}

• @Data注解的作用是自动生成getter、setter、equals、hashCode和toString等方法，无需我们再手动添加。

下面是加上@Data注解，经过编译后的User.class文件，可见它已经生成了getter、setter、equals、hashCode和toString等方法

//
// Source code recreated from a .class file by IntelliJ IDEA
// (powered by FernFlower decompiler)
//

package zoo.pojo;

import zoo.enmu.SexEnum;

public class User {
    private Long id;
    private String name;
    private Integer age;
    private String email;
    private SexEnum sex;

    public User() {
    }

    public Long getId() {
        return this.id;
    }

    public String getName() {
        return this.name;
    }

    public Integer getAge() {
        return this.age;
    }

    public String getEmail() {
        return this.email;
    }

    public SexEnum getSex() {
        return this.sex;
    }

    public void setId(final Long id) {
        this.id = id;
    }

    public void setName(final String name) {
        this.name = name;
    }

    public void setAge(final Integer age) {
        this.age = age;
    }

    public void setEmail(final String email) {
        this.email = email;
    }

    public void setSex(final SexEnum sex) {
        this.sex = sex;
    }

    public boolean equals(final Object o) {
        if (o == this) {
            return true;
        } else if (!(o instanceof User)) {
            return false;
        } else {
            User other = (User)o;
            if (!other.canEqual(this)) {
                return false;
            } else {
                label71: {
                    Object this$id = this.getId();
                    Object other$id = other.getId();
                    if (this$id == null) {
                        if (other$id == null) {
                            break label71;
                        }
                    } else if (this$id.equals(other$id)) {
                        break label71;
                    }

                    return false;
                }

                Object this$age = this.getAge();
                Object other$age = other.getAge();
                if (this$age == null) {
                    if (other$age != null) {
                        return false;
                    }
                } else if (!this$age.equals(other$age)) {
                    return false;
                }

                label57: {
                    Object this$name = this.getName();
                    Object other$name = other.getName();
                    if (this$name == null) {
                        if (other$name == null) {
                            break label57;
                        }
                    } else if (this$name.equals(other$name)) {
                        break label57;
                    }

                    return false;
                }

                Object this$email = this.getEmail();
                Object other$email = other.getEmail();
                if (this$email == null) {
                    if (other$email != null) {
                        return false;
                    }
                } else if (!this$email.equals(other$email)) {
                    return false;
                }

                Object this$sex = this.getSex();
                Object other$sex = other.getSex();
                if (this$sex == null) {
                    if (other$sex == null) {
                        return true;
                    }
                } else if (this$sex.equals(other$sex)) {
                    return true;
                }

                return false;
            }
        }
    }

    protected boolean canEqual(final Object other) {
        return other instanceof User;
    }

    public int hashCode() {
        int PRIME = true;
        int result = 1;
        Object $id = this.getId();
        int result = result * 59 + ($id == null ? 43 : $id.hashCode());
        Object $age = this.getAge();
        result = result * 59 + ($age == null ? 43 : $age.hashCode());
        Object $name = this.getName();
        result = result * 59 + ($name == null ? 43 : $name.hashCode());
        Object $email = this.getEmail();
        result = result * 59 + ($email == null ? 43 : $email.hashCode());
        Object $sex = this.getSex();
        result = result * 59 + ($sex == null ? 43 : $sex.hashCode());
        return result;
    }

    public String toString() {
        return "User(id=" + this.getId() + ", name=" + this.getName() + ", age=" + this.getAge() + ", email=" + this.getEmail() + ", sex=" + this.getSex() + ")";
    }
}

添加mapper

让UserMapper继承BaseMapper，这样无需我们手动添加就有了单表增删改查的很多函数。

public interface UserMapper extends BaseMapper<User> {
}

查询测试

@SpringBootTest

public class MybatisPlusTest {

@Autowired

private UserMapper userMapper;

@Test

public void testSelectList(){

//selectList()根据MP内置的条件构造器查询一个list集合，null表示没有条件，即查询所有

userMapper.selectList(null).forEach(System.out::println);

}

}

测试结果

在application.yml中配置日志输出

# 配置MyBatis日志
mybatis-plus:
configuration:
log-impl: org.apache.ibatis.logging.stdout.StdOutImpl