Eclipse Community Forums: TMF (Xtext) » Using Xtext DSL as a rule engine on runtime

Help

Home

Home » Modeling » TMF (Xtext) » Using Xtext DSL as a rule engine on runtime

Show: Today's Messages :: Show Polls :: Message Navigator

Using Xtext DSL as a rule engine on runtime [message #1821429]

Wed, 12 February 2020 22:26

Ihar Valnou

Messages: 1
Registered: February 2020

Junior Member

Dear Xtext experts,
Thanks a lot for such an awesome technology and tools built around it!
We are using an Xtext technology to build a custom DSL which allow us to use different conditions as part of a rule engine and get a result of such conditions by running a DSL interpreter on runtime.
Example of such condition is here:

if(doSomething()) {
     return  true;
} else {
     return false;
}

To run an interpreter we just create a model from our string conditions, load it as resource, get model and run interpreter.
Here it's a way we create and load our resource with a condition string:

XtextResourceSet resourceSet = injector.getInstance(XtextResourceSet.class);
resourceSet.addLoadOption(XtextResource.OPTION_RESOLVE_ALL, Boolean.TRUE);
resourceSet.createResource(URI.createURI(UUID.randomUUID().toString());
InputStream inputStream = new ByteArrayInputStream("condition as string");
resource.load(inputStream, resourceSet.getLoadOptions());

Could you help me with the following questions:
1. Do we use a ResourceSet in a proper way? Maybe some pieces of advice?
2. Do you see any possible issues (out of memory, timings etc)

Thanks in advance!

Report message to a moderator

Re: Using Xtext DSL as a rule engine on runtime [message #1821568 is a reply to message #1821429]

Sat, 15 February 2020 07:43

Christian Dietrich

Messages: 14669
Registered: July 2009

Senior Member

hi, here are a some remarks
- the uri should have your file extension.
- you can use Xtexts built-in StringInputStream
- the resolve all is not needed as xtext resolves proxies lazy. it would also not work (as expected) once you ever have more than one resource

- having a look at timeings / performance you should do if you consider to have huge files

Twitter : @chrdietrich
Blog : https://www.dietrich-it.de

Report message to a moderator

Re: Using Xtext DSL as a rule engine on runtime [message #1821705 is a reply to message #1821568]

Tue, 18 February 2020 20:54

Neeraj Bhusare

Messages: 177
Registered: July 2009
Location: Canada

Senior Member

Adding to Christians comments

> XtextResourceSet resourceSet = injector.getInstance(XtextResourceSet.class);
You could just do - XtextResourceSet resourceSet = new XtextResourceSet()

> resourceSet.addLoadOption(XtextResource.OPTION_RESOLVE_ALL, Boolean.TRUE);
ECoreUtil#resolveAll() gets called internally, which tries to resolve all the proxies in your model. It might not be a good idea to load the complete model in the memory right at the start, especially if its a deep hierarchy

> esourceSet.createResource(URI.createURI(UUID.randomUUID().toString());
The file extension in the URI is required for getting the Resource Factory. It needs to be registered if you are running your application in standalone mode

> resource.load(inputStream, resourceSet.getLoadOptions());
resource.load(new StringInputStream("condition as string"));

Hope this helps.

Twitter : @NeerajBhusare
Blog : https://nbhusare.github.io/
Best regards, Neeraj

Report message to a moderator