Templates
Consider a simpler mechanism of Imports first.
Templates allow users to share common elements between different projects and processes.
Templates can contain the same type of files which are used in a regular process payload, plus additional instructions on how to modify process’ data.
Process files will overwrite any template files with the same name, this way a user can “override” any resource provided by a template.
Additionally, using template aliases, it is possible to create Concord flows which don’t require sending a payload archive or having a GIT repository with flows and can be called with a simple HTTP request.
Creating a template
Template is a regular JAR or ZIP archive with the structure similar to a regular process payload.
For example, the ansible template has the following structure:
_callbacks/ # (1)
trace.py
processes/ # (2)
main.yml
_main.js # (3)
It contains additional resources needed for the ansible task (1), a folder with a flow definition (2) and a pre-processing script (3).
Template archive must be uploaded to a repository just like a regular artifact.
Pre-processing
If a template contains _main.js file, it will be executed by the
server before starting a process. The script must return a JSON
object which will be used as process variables.
For example, if _main.js looks like this:
({
entryPoint: "main",
arguments: {
message: _input.message,
name: "Concord"
}
})
then given this request data
{
"message": "Hello,"
}
the process variables will look like this:
{
"entryPoint": "main",
"arguments": {
"message": "Hello,",
"name": "Concord"
}
}
A special _input variable is provided to access source data from a
template script.
Usage
Template can be referenced with a template entry in process variables:
flows:
default:
- log: "${message} ${name}"
configuration:
template: "http://host/path/my-template.jar"
# or by using a maven repository
template: "mvn://groupId:artifactId:version"
Only one template can be used at a time.
The template parameter can also be specified in request JSON data
or profiles.
Templates also can be references by their aliases:
configuration:
template: "my-template"
The alias must be added using the template API.