Entity DSL

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Purpose

The Entity DSL facilitates the handling of persistence entities. Defining entities using the Entity DSL efficiently creates a clean entity model that contains all relevant semantic elements of the model text file. This semantic model is used to automatically transform the semantic information into proper Java code with the respective annotations for a persistence provider. Additionally, if the entity model is located within a project with OSBP nature, "Auto-DTOs" and services are generated as well. In this case, attributes that are added to entities will automatically be transferred to the "Auto-DTOs".

Overview

The main semantic elements of the Compex Entity DSL are the following:

• "Package" - the root element that contains all the other elements. A model can contain multiple packages.

• "Import" declarations - used to import external models or even Java classes.

• "Datatype" declarations - a way to define datatypes that can be used in entities and beans.

• "Entity" - the abstraction of a business model entity. It contains further elements such as properties and references.

• "Bean" - does not compile to a JPA Entity but to a Java Bean (POJO with getter and setter and PropertyChange-Support). Beans may be used as temporary containers in entity operations or can be embedded into JPA Entities.

• "Enum" - the abstraction for Java enums.

• "Property" - a reference to an embedded Bean, an Enum, a Java class or a simple datatype (as defined in the datatype declaration). Offers multiplicity.

• "Reference" - a reference to another Entity (or to another Bean in the case of a Bean). Offers multiplicity.

• "Operations" - similar to Java methods. The Xbase expression language can be used to write high-level code.

• "Annotations" can be placed on Entity, Property and Reference.

• "Comments" can be added to all elements.

Entity model files

Entity models are described in .entitymodel files. These files describe the entity model and are the basis for the code generation. Entity models may be split over several .entitymodel files containing packages in the same namespace. An .entityodel file may contain several packages with entities. However, from a performance point of view, a complex entity model may work better with more and smaller .entitymodel files than the same model crammed into few large files (or even a single file).

package

Entity model files must start with a package declaration. Packages are the root element of the Entity DSL grammar. Everything is contained in a package: Imports, Entities, Beans and Enums have to be defined inside the Package definition. One document can contain multiple packages with unique names. The elements a package can contain are Entities, Beans and Enums. Additionally, a package allows Import statements and the declaration of datatypes.

 package name {
    import importStatement;
    datatype datatypeDefinition;
    entities/beans/enums
 } align alignment

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Figure 1 - Entity model file - a package is the topmost element and contains other items.

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