What is the difference between a Repository and a DAO (Data Access Object) ?
The reason for the question was that in many repositories (real world projects and tutorials on the web) I could not see much difference to good old DAOs.
Let's say you we have a functionality which is grabbing customers out of your database - seems to be modern to call stuff like this "CustomerRepository" - I personally doubt that this is what DDD is aiming at.
I started searching on the web but it was not so easy to find a precise answers but finally I stumbled over a very good blog post with illustrative examples. You definitely should check this out. I just would like to abstract it by opposing different aspects of repositories and DAOs:
| Repository | DAO |
| "business interface" speaking ubiquitous domain language | "technical interface" contracting between data source and OO application |
| Close to domain | Close to data source |
| typically one per aggregate root | typically one per database table (or web service operation) |
| containing one or multiple DAOs | used by a repository |
| interfaces in domain layer | interfaces in infrastructure layer |
| parameters of interface methods are domain types | parameters of interface methods are reflecting the data source |
| implementations in infrastructure layer (lots of technical plumbing) | implementations in infrastructure layer (purely technical) |
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