Springboot learn seven spring affairs

a transaction control

@Service
public class CityServiceImpl implements CityService {

    @Autowired
    private CityMapper cityMapper;
    
    @Override
    @Transactional(value = "primaryTxMan", readOnly = true)
    public List<City> findByState(String state) {
        return this.cityMapper.findByState(state);
    }
}

@Transcational(readOnly=true) This annotation is generally written on the business class, or on its method, to add transaction control to it. When readOnly=true is added to the parentheses, it will tell the underlying data source that this is a read-only transaction. For JDBC, read-only transactions will have a certain speed optimization .

Two Transactional value

 The value here is mainly used to specify different transaction managers; it is mainly used to satisfy the existence of different transaction managers in the same system. For example, in Spring, two transaction managers, txManager1, txManager2, are declared.

The user can then specify a specific txManager as needed based on this parameter.

   Then some students will ask under what circumstances will there be multiple transaction managers? For example, in a system that needs to access multiple data sources or multiple databases, multiple transaction managers must be configured.