How to Configure Multiple Data Sources with MyBatis in Spring Boot

Adding Multiple Data Source Configuration

First set two database connections in application.properties:

spring.datasource.primary.jdbc-url=jdbc:mysql://localhost:3306/test1
spring.datasource.primary.username=root
spring.datasource.primary.password=123456
spring.datasource.primary.driver-class-name=com.mysql.cj.jdbc.Driver

spring.datasource.secondary.jdbc-url=jdbc:mysql://localhost:3306/test2
spring.datasource.secondary.username=root
spring.datasource.secondary.password=123456
spring.datasource.secondary.driver-class-name=com.mysql.cj.jdbc.Driver

Explanation and notes:

When configuring multiple data sources, add a name after spring.datasource (e.g., primary, secondary) to distinguish them; this prefix is used later during initialization.

Configuration keys differ between Spring Boot 2.x and 1.x: 2.x uses spring.datasource.secondary.jdbc-url, while 1.x uses spring.datasource.secondary.url. Mis‑matching these keys can cause errors such as

java.lang.IllegalArgumentException: jdbcUrl is required with driverClassName

.

The data source configuration format is the same regardless of whether you use JdbcTemplate, Spring Data JPA, or MyBatis.

Initializing Data Sources and MyBatis Configuration

Create a configuration class to load the properties, instantiate the data sources, and provide MyBatis factories for each.

@Configuration
public class DataSourceConfiguration {

    @Primary
    @Bean
    @ConfigurationProperties(prefix = "spring.datasource.primary")
    public DataSource primaryDataSource() {
        return DataSourceBuilder.create().build();
    }

    @Bean
    @ConfigurationProperties(prefix = "spring.datasource.secondary")
    public DataSource secondaryDataSource() {
        return DataSourceBuilder.create().build();
    }
}

Define separate MyBatis configuration classes for the primary and secondary data sources, using @MapperScan to bind mapper packages, sqlSessionFactory, and sqlSessionTemplate to each data source.

@Configuration
@MapperScan(
        basePackages = "com.didispace.chapter39.p",
        sqlSessionFactoryRef = "sqlSessionFactoryPrimary",
        sqlSessionTemplateRef = "sqlSessionTemplatePrimary")
public class PrimaryConfig {
    private final DataSource primaryDataSource;
    public PrimaryConfig(@Qualifier("primaryDataSource") DataSource primaryDataSource) {
        this.primaryDataSource = primaryDataSource;
    }
    @Bean
    public SqlSessionFactory sqlSessionFactoryPrimary() throws Exception {
        SqlSessionFactoryBean bean = new SqlSessionFactoryBean();
        bean.setDataSource(primaryDataSource);
        return bean.getObject();
    }
    @Bean
    public SqlSessionTemplate sqlSessionTemplatePrimary() throws Exception {
        return new SqlSessionTemplate(sqlSessionFactoryPrimary());
    }
}

@Configuration
@MapperScan(
        basePackages = "com.didispace.chapter39.s",
        sqlSessionFactoryRef = "sqlSessionFactorySecondary",
        sqlSessionTemplateRef = "sqlSessionTemplateSecondary")
public class SecondaryConfig {
    private final DataSource secondaryDataSource;
    public SecondaryConfig(@Qualifier("secondaryDataSource") DataSource secondaryDataSource) {
        this.secondaryDataSource = secondaryDataSource;
    }
    @Bean
    public SqlSessionFactory sqlSessionFactorySecondary() throws Exception {
        SqlSessionFactoryBean bean = new SqlSessionFactoryBean();
        bean.setDataSource(secondaryDataSource);
        return bean.getObject();
    }
    @Bean
    public SqlSessionTemplate sqlSessionTemplateSecondary() throws Exception {
        return new SqlSessionTemplate(sqlSessionFactorySecondary());
    }
}

Key points:

Use @MapperScan to specify the package containing entities and mappers for each data source, and to bind the corresponding sqlSessionFactory and sqlSessionTemplate.

Inject the correct DataSource into each configuration class via @Qualifier, matching the bean names defined in DataSourceConfiguration.

Define SqlSessionFactory and SqlSessionTemplate beans that reference the appropriate data source.

Entity and Mapper Definitions

For the primary data source:

@Data
@NoArgsConstructor
public class UserPrimary {
    private Long id;
    private String name;
    private Integer age;
    public UserPrimary(String name, Integer age) {
        this.name = name;
        this.age = age;
    }
}

public interface UserMapperPrimary {
    @Select("SELECT * FROM USER WHERE NAME = #{name}")
    UserPrimary findByName(@Param("name") String name);

    @Insert("INSERT INTO USER(NAME, AGE) VALUES(#{name}, #{age})")
    int insert(@Param("name") String name, @Param("age") Integer age);

    @Delete("DELETE FROM USER")
    int deleteAll();
}

For the secondary data source:

@Data
@NoArgsConstructor
public class UserSecondary {
    private Long id;
    private String name;
    private Integer age;
    public UserSecondary(String name, Integer age) {
        this.name = name;
        this.age = age;
    }
}

public interface UserMapperSecondary {
    @Select("SELECT * FROM USER WHERE NAME = #{name}")
    UserSecondary findByName(@Param("name") String name);

    @Insert("INSERT INTO USER(NAME, AGE) VALUES(#{name}, #{age})")
    int insert(@Param("name") String name, @Param("age") Integer age);

    @Delete("DELETE FROM USER")
    int deleteAll();
}

Testing the Configuration

Write a test class to verify that each mapper operates against its designated data source.

@Slf4j
@RunWith(SpringRunner.class)
@SpringBootTest
@Transactional
public class Chapter39ApplicationTests {

    @Autowired
    private UserMapperPrimary userMapperPrimary;

    @Autowired
    private UserMapperSecondary userMapperSecondary;

    @Before
    public void setUp() {
        // Clean tables before each test
        userMapperPrimary.deleteAll();
        userMapperSecondary.deleteAll();
    }

    @Test
    public void testMultipleDataSources() throws Exception {
        // Insert into primary
        userMapperPrimary.insert("AAA", 20);
        UserPrimary userPrimary = userMapperPrimary.findByName("AAA");
        Assert.assertEquals(20, userPrimary.getAge().intValue());
        // Verify not present in secondary
        UserSecondary userSecondary = userMapperSecondary.findByName("AAA");
        Assert.assertNull(userSecondary);

        // Insert into secondary
        userMapperSecondary.insert("BBB", 20);
        // Verify not present in primary
        userPrimary = userMapperPrimary.findByName("BBB");
        Assert.assertNull(userPrimary);
        // Verify present in secondary
        userSecondary = userMapperSecondary.findByName("BBB");
        Assert.assertEquals(20, userSecondary.getAge().intValue());
    }
}

The complete example code is available in the chapter3-9 directory of the GitHub or Gitee repositories.