Dmitry Serebrennikov's Library tagged java →  View Popular

1. Use an optimised HQL query to return only the columns you
   really need.








Generally, the first option isn't greatly appreciated by the client. So
lets look at the second option. This approach involves determining exactly
which columns you really need, and instanciating data-transfer JavaBean objects
containing exactly those columns.


select new CityItem(city.id, city.name, city.electrityCompany.name)
from City city
...







This technique is fast and efficient, and avoids the overheads of handling
associated objects and of loading large numbers of persistent objects
into the Hibernate session cache. The only downside is the need to create
a dedicated data-transfer class for each query.

Ease of configuration. 
Spring's bean factory makes it easy to configure marshallers, without needing to construct JAXB context,
JiBX binding factories, etc. The marshallers can be configured as any other bean in your application
context. Additionally, XML Schema-based configuration is available for a number of marshallers, making
the configuration even simpler.

Consistent Interfaces. 
Spring's O/X mapping operates through two global interfaces: the
Marshaller and Unmarshaller interface.
These abstractions allow you to switch O/X mapping
frameworks with relative ease, with little or no changes required on the classes that do the
marshalling. This approach has the additional benefit of making it possible to do XML marshalling with
a mix-and-match approach (e.g. some marshalling performed using JAXB, other using XMLBeans) in a
non-intrusive fashion, leveraging the strength of each technology.

Consistent Exception Hierarchy. 
Spring provides a conversion from exceptions from the underlying O/X mapping tool to its own exception
hierarchy with the XmlMappingException as the root exception. As can be expected,
these runtime exceptions wrap the original exception so no information is lost.