Implement ORM mapping based on Spring Boot and MyBatis Plus

In the development process of Java web applications, ORM (Object-Relational Mapping) mapping technology is used to map relational data in the database to Java objects, making it convenient for developers to access and operate data. Spring Boot, as one of the most popular Java web development frameworks at present, has provided a way to integrate MyBatis, and MyBatis Plus is an ORM framework extended on the basis of MyBatis. This article will introduce how to use Spring Boot and MyBatis Plus to implement ORM mapping.

1. Spring Boot integrates MyBatis Plus
Using MyBatis Plus in Spring Boot is very simple, just add the dependency of MyBatis Plus to maven.

<dependency>
  <groupId>com.baomidou</groupId>
  <artifactId>mybatis-plus-boot-starter</artifactId>
  <version>3.4.2</version>
</dependency>

At the same time, configure MyBatis Plus related parameters in application.properties or application.yml, as shown below:

#数据库配置
spring.datasource.driver-class-name=com.mysql.cj.jdbc.Driver
spring.datasource.url=jdbc:mysql://localhost:3306/mybatis_plus?useUnicode=true&characterEncoding=UTF-8&serverTimezone=UTC
spring.datasource.username=root
spring.datasource.password=123456
#MyBatis Plus配置
mybatis.configuration.cache-enabled=false
mybatis.mapper-locations=classpath:mapper/*.xml

Among them, driver-class-name, url, username and password are databases Related configuration, and mapper-locations is the path where the SQL mapping configuration file of MyBatis Plus is located.

2. Define entity classes and Mapper interfaces
Like MyBatis, using MyBatis Plus also requires defining entity classes and Mapper interfaces. The following takes a simple User table as an example to define the corresponding entity class and Mapper interface.

1. Define entity classes

@Getter
@Setter
@Builder
@NoArgsConstructor
@AllArgsConstructor
public class User {

    private Integer id;
    private String name;
    private Integer age;
    private String email;
    private Integer gender;
    private LocalDateTime createTime;
    private LocalDateTime updateTime;

}

Using the annotations @Getter, @Setter and @Builder can simplify the code, while @NoArgsConstructor and @AllArgsConstructor are used to generate parameter-free and full Parameter constructor.

2. Define Mapper interface

public interface UserMapper extends BaseMapper<User> {
}

The BaseMapper provided by MyBatis Plus is used here, which can save many tedious SQL operations.

3. Use MyBatis Plus for database operations
After defining the Mapper interface, you can use MyBatis Plus for database operations.

1. Insert data

User user = User.builder()
        .name("test")
        .age(20)
        .email("test@test.com")
        .gender(1)
        .createTime(LocalDateTime.now())
        .updateTime(LocalDateTime.now())
        .build();
int count = userMapper.insert(user);

When inserting data, you can directly use the insert method provided in the Mapper interface. MyBatis Plus will automatically map the attributes of the entity class to the database. corresponding column.

2. Query data

List<User> userList = userMapper.selectList(null);

When querying data, you can directly use the selectList method provided in the Mapper interface and pass in null or an empty QueryWrapper object to query it. All data. In addition, you can also use lambda expressions and chain operations provided by MyBatis Plus to perform more complex queries, as shown below:

QueryWrapper<User> wrapper = Wrappers.<User>lambdaQuery()
        .eq(User::getGender, 1)
        .ge(User::getAge, 20)
        .orderByDesc(User::getCreateTime);
List<User> userList = userMapper.selectList(wrapper);

In the above code, use Wrappers.lambdaQuery() A QueryWrapper object is defined, and query conditions and sorting rules are constructed through .eq, .ge and .orderByDesc chain operations.

3. Update data

User user = userMapper.selectById(id);
user.setAge(30);
int count = userMapper.updateById(user);

When updating data, you can first query the data that needs to be updated through selectById, then modify the attributes that need to be updated, and use updateById to The modified data is updated to the database.

4. Delete data

int count = userMapper.deleteById(id);

Finally, when deleting data, just call the deleteById method provided in the Mapper interface.

4. Conclusion
This article introduces how to use Spring Boot and MyBatis Plus to implement ORM mapping, and database operations can be achieved through simple configuration and code. MyBatis Plus, as an extension framework of MyBatis, can greatly simplify the developer's workload while improving the readability and maintainability of the code. Due to space limitations, this article only introduces the basic usage of MyBatis Plus. For more advanced functions, please refer to the official documentation.

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