springboot-support

some extended supports for SpringBoot

multi-datasource

Support multi-datasource for SpringBoot.

How To Enable Multi-DataSource Support?

Just do it in a SpringBoot way:

@Configuration
@EnableMultiDataSource
public class XXXConfiguration {
  // code...
}

or

@SpringBootApplication
@EnableMultiDataSource
public class XXXApplication {
  // code...
}

In purpose to specify your configuration of multi-datasource, inside EnableMultiDataSource you can change:

• location: location of configuration properties, default classpath:application.properties.
• prefix: prefix of configuration, default multi-datasource.multi.
• loader: class of loader to load configuration properties, default DefaultPropertiesLoader; If some ConfigurationService, like Spring Cloud Config or Aliyun ACM, is in use, change loader to a customized loader class implementing PropertiesLoader interface to load it in your way.

How To Configure Multi-DataSource?

Configuration properties is parsed by PropertiesParser. As a convention, every item will be treated in a <prefix>.<name>.<config>.<property> pattern:

• prefix: prefix defined in EnableMultiDataSource
• name: base name of DataSource and JdbcTemplate beans, thus generating bean names in pattern <name>DataSource and <name>JdbcTemplate
• config: a sub-name for detail config properties of DataSource, candidates is below
  • datasource: basic config properties, bind to DataSourceProperties
  • hikari: Hikari config, bind to com.zaxxer.hikari.HikariDataSource
  • tomcat: Tomcat config, bind to org.apache.tomcat.jdbc.pool.DataSource
  • dbcp2: Dbcp2 config, bind to org.apache.commons.dbcp2.BasicDataSource
• property: property name in DataSourceProperties; We reuse utilized classes DataSourceProperties and DataSourceBuilder in SpringBoot to construct DataSource and JdbcTemplate

Type of DataSource will be determined by SpringBoot automatically if not specified in properties, just like spring-boot-starter-jdbc does.

Example:

multi-datasource.multi.a.datasource.url = jdbc:mysql://localhost:3306/test
multi-datasource.multi.a.datasource.username=test
multi-datasource.multi.a.datasource.password=123456
multi-datasource.multi.a.datasource.driver-class-name=com.mysql.cj.jdbc.Driver

multi-datasource.multi.b.datasource.url = jdbc:mysql://localhost:3306/test
multi-datasource.multi.b.datasource.username=test
multi-datasource.multi.b.datasource.password=123456
multi-datasource.multi.b.datasource.driver-class-name=com.mysql.cj.jdbc.Driver
multi-datasource.multi.b.hikari.maximum-pool-size = 3

This will lead to construction of:

• 2 DataSources with bean names: aDataSource and bDataSource
• 2 JdbcTemplates with bean names: aJdbcTemplate and bJdbcTemplate

How To Inject DataSource/JdbcTemplate?

Beans depending on a DataSource or JdbcTemplate must be annotated by DataSourceRouting, and value should be one of base names parsed from configuration properties. Besides, to accept DataSource or JdbcTemplate specified by DataSourceRouting, bean also must satisfied one of the following convention:

• implement interface DataSourceAware or JdbcTemplateAware.
• own a method named as setDataSource or setJdbcTemplate.

Example:

@DataSourceRouting("a")
public class JdbcTemplateAwareBean implements JdbcTemplateAware {
  private JdbcTemplate jdbcTemplate;
  @Override
  public void setJdbcTemplate(JdbcTemplate jdbcTemplate) {
    this.jdbcTemplate = jdbcTemplate;
  }
}

or

@DataSourceRouting("a")
public class JdbcTemplateSetterBean {
  private JdbcTemplate jdbcTemplate;
  public void setJdbcTemplate(JdbcTemplate jdbcTemplate) {
    this.jdbcTemplate = jdbcTemplate;
  }
}

Injection of DataSource and JdbcTemplate is processed by DataSourceRoutingPostProcessor, which will detect interfaces and methods introduced above and do the injection.