Spring Boot (11) : Spring Boot integration MyBatis

During project startup, the Spring Boot Starter loads and initializes components based on convention information. Therefore, the introduction of the Starter for the project can be achieved out of the box. So mybatis-spring-boot-starter can help you quickly build a MyBatis application based on Spring Boot.

⭐ next to get you started integrating MyBatis in the Spring Boot project!

Import the following dependencies into the POM.xml file:

<! -- MyBatis Integration With Spring Boot -->
<dependency>
    <groupId>org.mybatis.spring.boot</groupId>
    <artifactId>mybatis-spring-boot-starter</artifactId>
    <version>2.2.0</version>
</dependency>

<! -- @data, @tostring -->
<dependency>
    <groupId>org.projectlombok</groupId>
    <artifactId>lombok</artifactId>
    <version>1.18.12</version>
    <scope>provided</scope>
</dependency>

<! Mysql driver -->
<dependency>
    <groupId>mysql</groupId>
    <artifactId>mysql-connector-java</artifactId>
    <version>8.0.16</version>
</dependency>

<! -- log4j prints SQL execution logs,.yml configuration -->
<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-log4j</artifactId>
    <version>1.3.8. RELEASE</version>
</dependency>
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Note: this dependency is provided by MyBatis official integration with Spring Boot, not Spring Boot official integration with MyBatis, so the

version number cannot be omitted!

As we all know, MyBatis has two core components: SqlSessionFactory and Mapper interface. The former is used for database connections and the latter for SQL mappings. When we use MyBatis based on Spring, we also want to ensure that these two components are present in the Spring environment.

After the mybatis-spring-boot-starter dependency is introduced, it will automatically complete the following tasks:

1. Automatic detection of existingDataSource
2. usingSqlSessionFactoryBeanCreate and registerSqlSessionFactory
3. Create and registerSqlSessionTemplateThe instance
4. Automatic scanningMappersInterface and register it in the Spring context for easy injection

Mysql > select * from sys_user;

Create the User entity class

Note: the entity class name User does not match the sys_USER table name in the database, so it cannot be mapped automatically. Therefore, manual mapping should be carried out through the resultType attribute when usermapper. XML is written. Phone and phoneNum are mapped through the AS alias in the Select statement.

@Data
@ToString
public class User {
    private int id;
    private String username;
    private String email;
    private String password;
    private String phone;

}
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Mapper interfaces:

@Mapper
public interface UserMapper {
    List<User> selectAllUsers(a);
}
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🧠 If you have more than one @mapper, it is a bit troublesome to annotate one by one. In this case, you can use @mapperscan (basePackages = “com.wyk.mybatis. Dao “) instead.

@Configuration
@MapperScan(basePackages = "com.wyk.mybatis.dao")
public class MyBatisConfiguration {}Copy the code

For SQL statements, we can write them as annotations or as XML configuration files, which are used here to demonstrate:

Front: in the resource directory com/wyk/new mybatis mapper/UserMapper. The XML mapping file.

      
<! DOCTYPEmapper PUBLIC "- / / mybatis.org//DTD Mapper / 3.0 / EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.wyk.mybatis.dao.UserMapper">

    <select id="selectAllUsers" resultType="user">-- phoneNum As phone: select ID, username, email, password, phoneNum As phone -- Mapping with inconsistent table names from sys_user;</select>

</mapper>
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The SQL mappings are basically configured, but the database is not connected yet, so you configure them in application.yml.

spring:
  datasource:
    url: jdbc:mysql://localhost:3306/mybatis? useUnicode=true&characterEncoding=UTF-8&serverTimezone=Asia/Shanghai
    driver-class-name: com.mysql.cj.jdbc.Driver
    username: root
    password: 123456
mybatis:
  # Entity category name -- package path
  type-aliases-package: com.wyk.mybatis.entity
  # map file location
  mapper-locations: classpath*:com/wyk/mybatis/mapper/*Mapper.xml
  configuration:
    Print SQL statements using logs
    log-impl: org.apache.ibatis.logging.stdout.StdOutImpl

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OK! Next test in the test class:

@SpringBootTest
class MybatisApplicationTests {

    @Autowired
    private UserMapper userMapper;

    @Test
    void contextLoads(a) { List<User> users = userMapper.selectAllUsers(); users.forEach(System.out::println); }}Copy the code

Running results:

🤨Spring Boot integrated MyBatis basic operations on this demonstration, more operations and configuration please refer to the official documentation