Spring Boot configures multiple DataSources

DataSourceWhen using Spring Boot, configuration is very easy by default . Spring Boot will automatically configure one for us DataSource.

If the relevant configuration application.ymlis specified in spring.datasource, Spring Boot will create one with that configuration DataSource. If there application.ymlis no spring.datasourcerelated configuration specified in , Spring Boot will search the classpath for jar packages of in-memory databases such as H2 and hsqldb. If found, an in-memory database will be automatically configured DataSource, so we only need to introduce the jar package. For example, to configure an hsqldb data source:

<dependency>
    <groupId>org.hsqldb</groupId>
    <artifactId>hsqldb</artifactId>
    <scope>runtime</scope>
</dependency>

However, in some cases, if we need to configure multiple data sources, how should we configure it in Spring Boot?

We take JDBC as an example to demonstrate how to configure both in Spring Boot DataSource. Correspondingly, we will create two JdbcTemplatebeans to use these two data sources respectively.

First, we have application.ymlto declare the configuration for two data sources in, one using spring.datasourceand the other using spring.second-datasource:

spring:
  application:
    name: data-multidatasource
  datasource:
    driver-class-name: org.hsqldb.jdbc.JDBCDriver
    url: jdbc:hsqldb:mem:db1
    username: sa
    password:
  second-datasource:
    driver-class-name: org.hsqldb.jdbc.JDBCDriver
    url: jdbc:hsqldb:mem:db2
    username: sa
    password:

Both DataSourceof these use hsqldb, but the databases are different. In addition, when using multiple data sources, all necessary configurations cannot be omitted.

Second, we need to create two DataSourcebeans ourselves, one marked @Primaryand the other named secondDatasource:

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

    @Bean(name = "secondDatasource")
    @ConfigurationProperties(prefix = "spring.second-datasource")
    public DataSource secondDataSource() {
        return DataSourceBuilder.create().build();
    }
}

For each of them DataSource, we have to @ConfigurationProperties(prefix = "xxx")specify the prefix of the configuration item.

Next, we create two JdbcTemplatebeans, one of which is marked and the @Primaryother named secondJdbcTemplate, using the corresponding DataSource:

@Bean
@Primary
public JdbcTemplate primaryJdbcTemplate(DataSource dataSource) {
    return new JdbcTemplate(dataSource);
}

@Bean(name = "secondJdbcTemplate")
public JdbcTemplate secondJdbcTemplate(@Qualifier("secondDatasource") DataSource dataSource) {
    return new JdbcTemplate(dataSource);
}

Note that secondJdbcTemplatewhen creating, the incoming DataSourcemust be @Qualifier("secondDatasource")declared, so that the second one can be used DataSource.

Now , we have created two JdbcTemplate. BeanWhere we need to use the first JdbcTemplate, we inject directly:

@Component
public class SomeService {
    @Autowired
    JdbcTemplate jdbcTemplate;
}

Where we need to use the second one JdbcTemplate, we need to use the flag when injecting @Qualifier("secondJdbcTemplate"):

@Component
public class AnotherService {
    @Autowired
    @Qualifier("secondJdbcTemplate")
    JdbcTemplate secondJdbcTemplate;
}

In this way, we can use different JdbcTemplateoperations for different data sources.

Precautions

When there are multiple beans of the same type, for example, multiple DataSource, multiple JdbcTemplate, it is strongly recommended to always use @Primaryone of the beans marked as "primary", and the bean @Autowiredmarked as the first will be used when using injection @Primary.

For other beans of the same type, each one needs to use an @Bean(name="xxx")identifying name, and when using @Autowiredinjection, @Qualifier("xxx")specify the name of the injected bean.

For the complete sample project source code, please refer to:

https://github.com/michaelliao/springcloud/tree/master/data-multidatasource