Is an ORM applicable for a non-CRUD database?

Question

I'm pretty new to database development in general and I've never used ORM before. I'm interested in the benefits of using one, specifically saving time writing boilerplate SQL queries. I'd like to use ORM for a project that I'm working on right now, but I'm not sure it's applicable.

This project is more akin to change tracking for very small (<= 500 characters) documents. I need to track edits and categorizations made by multiple users. Not really to see the specific changes they make, but more to see if the users agree with each other. I am using a SQL database for this (as opposed to actual document control) for a few reasons:

1. The documents are really small; and I'm only interested in the strings, not really in files.
2. I wanted the ability to perform ad-hoc queries against the data for development purposes, and didn't want an unpleasantly surprised halfway through that a particular document control package couldn't do what I wanted.

From most of what I've read it seems like you need a direct mapping from columns to data fields in an object to use ORM. What I have now does not even come close to this. To create objects representing documents in different stages of editing I have to cobble together data from columns in different tables, in different combinations.

So my question is: Does an ORM like Hibernate apply to this type of project? And if it does can one be added to an existing application/database?

If it makes a difference: I'm using Java, MySQL, and JDBC. The web app users have access to for edits is made with GWT and hosted via Tomcat6. If I need it, I have complete control of the webserver.

Thanks.

Answer 1

My opinion is that an ORM tool could be useful for you but you really need to delve into it to see for yourself. Remember when you use an ORM tool you are not forced to use only that to connect to your database. ORM tools in general make the most sense for applications that store data in a very object like structure. For instance your user code might be the place to start. Usually you only create 1 user at a time, you edit 1 user at a time, you check if 1 user is logged into. It also makes sense for things where you would return a list of results like Order Lines. Where I have run into issues with ORM tools is when you have complex data that requires multiple joins especially back to the table you started in. For those cases you might want to keep doing what you are doing. Overall, ORM tools are great but they are like a lot of other things in software development. Try them out on a small part of your code and use them where they work and don't where they don't. Ultimately, you are the one that will have to deal with and maintain whatever you make. Just educate yourself on Hibernate and I am sure you will know what to do!

Answer 2

Does an ORM like Hibernate apply to this type of project?

Yes

And if it does can one be added to an existing application/database?

Yes

Answer 3

I think that ORM (I would suggest using the JPA standard, probably with Hibernate as the provider) could suit your project.

It is fairly traditional, as you say, for database columns to map directly onto object fields. If you need to keep your existing database structure (which apparently doesn't map at all well to your objects), then you might find that its more trouble than it's worth to use ORM.

While it's certainly possible to use ORM to map to a specific database schema - perhaps because it's used by other systems - my view is that one of the biggest advantages of ORM is that you can almost ignore the schema. Once you design your objects, and tell hibernate about them, hibernate will create whatever tables it needs.