bluedenim / multids-demo

Demo Spring Boot app using multi (two) datasources

multids-demo

A sample Spring Boot app showing how to configure one to use multiple DataSources.

Probably one of the more common questions people (myself included) have about Spring Boot. Sooner or later you will run into a situation when you need to work with two databases.

The Spring Boot documentation is concise, perhaps as a way to illustrate how easy it is to work with it. However, it is surprising how little documentation there is on working with multiple DataSources.

This sample all shows how it can be done.

The main points, if looking through the app is too much for you:

• Add a Configuration class (anywhere in the tree where it can be scanned by Spring Boot, typically a sibling of your @SpringBootApplication class (com.van.MultiDatasourceDemoApplication in this app).
• In that Configuration class (com.van.DataSourceConfiguration in this app):
  • Declare a @Bean method to return a DataSource for each data source.
  • If you want to configure the data sources via the environment (e.g. application.properties and the like), add @ConfigurationProperties(prefix="...") with the prefix for your properties.
  • One of the data sources need to be annotated with @Primary for it to be the default data source (or you may encounter errors during start-up).
  • The method can return any implementation of DataSource, though I use org.apache.tomcat.jdbc.pool.DataSource so that all the connection pool parameters are also available.
• Configure the data sources in application.properties (or other environmental means)
• When using the datasources, Autowire them in as usual (see com.van.services.DataAccessService).
  • Without further qualifiers, the default datasource is used just as before.
  • With a qualifier (such as @Resource(name="...")), you can select the data source you want.

That's pretty much it. The rest of the app is basically some boilerplate stuff so that you can run it (mvn spring-boot:run) and see it in action with http://localhost:8080/.

Building & Running

You will need:

• Java 1.8
• Maven (3.2.2 tested)

Simply clone the repo and run with Maven:

mvn spring-boot:run

Then simply visit http://localhost:8080/ to see the queries made of the datasources printed out.