Not an actual Spring-related subject
We need help about a subject that came up in our project in a very annoying way.
I would like to say that the following has little to do with Spring properly, in the sense that it is a design/architecture decision rather than a technological problem, but I think that the Spring community is as good a place as every other to ask such questions in order to get feedback from experienced, talented and on-the-same-page developers. So, without further due, Iíll get to the point.
We are developing a large system; I mean a nation-wide large system, which of course manages a lot of business entities. There is a certain subset of said entities that must be audited every time one is added, deleted or updated. The problem here is the special nature of these audits. See, we are not looking at a text-only solution in the form of ďUser X did operation Y to entity ZĒ but we must actually store the entity being updated or saved in order to fulfill a detailed view requirement in one of our use cases that asks for the full history of changes of an user-selected attribute of one of the entities audited. For instance, if one such an entity were a Person class, an user could ask for all the states the name or hairColor attributes has had since the Person object with id 456 was created. This issue grows even bigger when we take into account that this is probably true ALSO for lists or sets of attributes.
We are using Spring 2.0.6 (our project framework ensemble was defined from above, using a template from a previous project, so we donít have the choice to advocate for Spring 2.5 right now) Hibernate 3.x and JSF. We also use Acegi 1.0.x for security (although we heavily modified it for special requirements of security we have and also to support AJAX) and other less relevant frameworks. Our DBMS is Oracle 10g.
Initially we thought in serializing all the traffic between the application and the database, and coded a solution accordingly. But although we havenít tested the code in real situations, itís obvious this is a huge pull down on performance, not to mention database disk space. We are using a Hibernate Interceptor injected into the Transaction Manager to hold the problematic code. This way we have a chance to get in the way of every transaction that is made to the database via Hibernate, leaving out native SQL queries, HQL and stored procedures (the latest we handle using Spring support, it was by far easier to comprehend and to use than Hibernateís).
So current solution is as follows:
Every time an Auditable entity is saved, we serialized it and stored it in this format in a BLOB field.
Every time an Auditable entity is updated, we loop through all of its attributes seeing which one of them changed (the Hibernate interceptor provides two arrays for this, one with current values and one with old values) and if it has, then if itís a plain attribute or a wrapper, we store it as a ModificationAttribute object, containing the name of the property and its value; if itís an Object, we serialize it into another implementation of ModificationAttribute, and if itís a Collection of any kind, we serialize the object(s) that caused the Collection to change into ModificationAttribute(s). The the UpdateAudit and its accompanying list of Modification attributes is save to the database at the commit phase in the same interceptor. Problems with these approach are obvious, we are imposing a huge hit in performance in the application as well as in the storage capacity of the database. We have thought a lot about this, but the requirements are adamant and we are always forced to go through all the attributes in the entities. What I need is some insight of experience about something similar to these, or at the very least another way to store an object through several updates in a way that allows it to be rebuilt as it was at any given point of time.
The complete solution is larger than this, but this is the problematic part.
Iím sorry Iím posting this in the Spring forum which is supposed to be devoted to technical discussion of Spring features, but I thought this was as good a place to ask for help as any other. And after all, Iím also a Spring user, albeit a very lame one. Iím not posting code or XML due to confidentiality constraints, but Iíll be glad to address any concern you may have in the clearest way possible. I also apologize for my poor English.
Thanks in advance