jOOQ exposes a lot of interfaces and hides most implementation facts from client code. The reasons for this are:
- Interface-driven design. This allows for modelling queries in a fluent API most efficiently
- Reduction of complexity for client code.
- API guarantee. You only depend on the exposed interfaces, not concrete (potentially dialect-specific) implementations.
The org.jooq.impl.DSL class is the main class from where you will create all jOOQ objects. It serves as a static factory for table expressions, column expressions (or "fields"), conditional expressions and many other QueryParts.
With jOOQ 2.0, static factory methods have been introduced in order to make client code look more like SQL. Ideally, when working with jOOQ, you will simply static import all methods from the DSL class:
import static org.jooq.impl.DSL.*;
Note, that when working with Eclipse, you could also add the DSL to your favourites. This will allow to access functions even more fluently:
concat(trim(FIRST_NAME), trim(LAST_NAME)); // ... which is in fact the same as: DSL.concat(DSL.trim(FIRST_NAME), DSL.trim(LAST_NAME));