Brainstorming on introducing "Stacks"

At the moment Forge generates code without having a real notion of a technical stack. For example, creating a JPA Entity for a Java EE 6 application could be different from a Java EE 7 application :

• The persistence.xml version if different (2.0 / 2.1)
• The properties are different (e.g. schema generation in 2.1)
• The syntax is different (List<MyEntity> m = new ArrayList<MyEntity> while it could use diamond syntax for a Java EE 7 stack)

The stack could be choosen when the project is created :

• project-new --named myproj : let's the developper use Forge without any special stack
• project-new --named myproj --stack JavaEE7 : the generated code will follow Java EE 7

Possible stacks

A stack would bundle certain facets. Therefore we could have as many stacks as needed. As an example, we could have the following stacks :

• Java EE 6 : JPA 2.0, CDI 1.0, JSF 2.0, Bean Validation 1.0, JTA 1.1
• Java EE 7 : JPA 2.1, CDI 1.1, JSF 2.2, Bean Validation 1.1, JTA 1.2, Batch 1.0
• Micro Java EE 7 Service: JPA 2.1, CDI 1.1, JSF 2.2, Bean Validation 1.1, JTA 1.2, Batch 1.0 (but with special Microservice configuration)
• Java EE 8 : JPA 2.1, CDI 2.0, JSF 2.3, Bean Validation 1.2, JTA 1.2, Batch 1.0, JCache 1.1, MVC 1.0
• Spring 3.x
• Spring 4.x
• ....

Differences in having stacks

Filtering commands

When you pick up a Stack, it gives you access or not to certain commands. For example, if you create a project with a Java EE 6 stack, you won't have access to any Batch, MVC... commands

$ project-new --named myproj --stack JavaEE6
$ jpa-new-entity --named MyEntity

$ project-new --named myproj --stack JavaEE7
$ jpa-new-entity --named MyEntity
$ mvc-new-controller --named MyController // only available on EE7

Setting up command versions

When you pick up a Stack, it filters the commands that have the right version for the right stack. For example, if you create a Java EE 6 stack, you will get JPA 2.0 commands, for a Java EE 7 stack, the JPA 2.1 commands. Also, the version parameters will be disabled

$ project-new --named myproj
$ jpa-new-entity --named MyEntity --jpaVersion 2.1
$ cdi-new-bean --named MyBean --cdiVersion 1.1

$ project-new --named myproj --stack JavaEE6
$ jpa-new-entity --named MyEntity  // no --jpaVersion because it is automatically set to 2.0

$ project-new --named myproj --stack JavaEE7
$ jpa-new-entity --named MyEntity  // no --jpaVersion because it is automatically set to 2.1
$ jpa-new-converter --named MyConvert  // JPA Converters are only available in 2.1

API to define a Stack

A stack could be defined with a fluent API such as :

stack("JavaEE7").includes(JavaEE7Facet).includes(JPA2.1Facet).excludes(SpringFacet)
stack("JavaEE7").includes(JavaEE7Facet).includes(JPA2.1Facet).allowsFeature(WildflySwarm)
stack("MyOwnStacks").includes(JavaEE7Stack).includes(MyFacet).includes(YourFacet)