soft exception handling of BeanCreationException for spring JPA repository

Question

I am building a service that is supposed to be elastic and resilient enough based on data sources available when SpringBootApplication launches.

E.g. when datasource for FooRepository is online, then proceed and launch FooService; when datasource for BarRepository is online, then proceed and launch BarService. If one of the data sources is offline (like network issue or terminiation), the ignore and continue with the rest of the Repositories/Services, instead of failing the launching.

Any idea of how to achieve this?

question from:https://stackoverflow.com/questions/65866662/soft-exception-handling-of-beancreationexception-for-spring-jpa-repository

Answer 1

Usually this kind of things can be achieved by using @Conditional and its derivatives.

In one sentence this feature allows loading the bean (and making it available for injection into other beans) only if it obeys some condition. Usually its some kind of property or maybe presence of another bean, however in a nutshell you can define an implementation by yourself.

This is a tutorial about conditionals. More precisely you'll need a paragraph about the custom conditions

So you might define the condition that will "check the availability of the data source" and will return true from its matches method.

One caveat is that if you don't load, say DAO because the condition is not matched, then the code of the service that might use this Dao will fail because there is no bean of Dao available for injection.

So you might want either to load the no-op dao implementation when the condition is not met, or maybe not load the service itself, this really depends on the real project implementation.