Question

I am using @Transactional on my service class which call DAO methods
and I was wondering how can I use read only on specific service method.
Do I have to define extra @Transactional with readonly=true on this service method, or there’s another way?

Answer 1

From the Spring API here.

The most derived location takes precedence when evaluating the transactional settings for a method. In the case of the following example, the DefaultFooService class is annotated at the class level with the settings for a read-only transaction, but the @Transactional annotation on the updateFoo(Foo) method in the same class takes precedence over the transactional settings defined at the class level.

@Transactional(readOnly = true)
public class DefaultFooService implements FooService {

  public Foo getFoo(String fooName) {
    // do something
  }

  // these settings have precedence for this method
  @Transactional(readOnly = false, propagation = Propagation.REQUIRES_NEW)
  public void updateFoo(Foo foo) {
    // do something
  }
}

The @Transactional annotation is metadata that specifies that an interface, class, or method must have transactional semantics; for example, “start a brand new read-only transaction when this method is invoked, suspending any existing transaction”. The default @Transactional settings are as follows:

Propagation setting is PROPAGATION_REQUIRED.

Isolation level is ISOLATION_DEFAULT.

Transaction is read/write.

Transaction timeout defaults to the default timeout of the underlying transaction system, or to none if timeouts are not supported.

Any RuntimeException triggers rollback, and any checked Exception does not.