z2-Environment

h1. More efficient handling of API and Impl in Rebuilds

Currently, in the dependency map used by the ComponentsBuilder, we analyze the necessity of a rebuild by comparing

build timestamps maintained in a dependency map in dependent components with a latest built timestamp kept in the

build lock file of the dependency component.

If there is a rebuild of an implementation part of a Java component, the build timestamp is updated and so a

rebuild of all dependency components forced - which is unnecessary, unless there was a change in the API as well.

We would like that a rebuild of dependency Java components is not forced, if there is no change of the API of a dependency component

h2. With the current model

At the level of the dependency component:

* Separate build timestamps for API and implementation as maintained in the build lock file.

At the level of the dependent component:

* When checking for rebuild in dependency components only check for matches with the API build timestamp.

* Keep a cache of build results and copy from there, if no deemed necessary - because the sources are not younger than the last build-timestamp

h2. A new component split

The solution would be altogether completely natural, if api and impl as well as test would be different "Java" components.

We could have a simple layout:

<pre>

<module>/api

<module>/impl

</pre>

For compatibility, we could consider

<pre>

<module>/impl -(private)-> <module>/java/impl

<module>/java -(public)->  <module>/java/api

</pre>