[jboss-jira] [JBoss JIRA] Commented: (JBRULES-1675) Xpath Default Constraint Evaluations

Xpath Default Constraint Evaluations ------------------------------------ Key: JBRULES-1675 URL: https://issues.jboss.org/browse/JBRULES-1675 Project: Drools Issue Type: Feature Request Security Level: Public(Everyone can see) Components: drools-compiler, drools-compiler (expert), drools-eclipse Reporter: Paul Ryan Assignee: Mark Proctor A default set of constraint matchers for xpath based on loaded w3c DOMs would be very helpful. For our project we have alot of facts that are just an xml file (this seems to be the way the industry in general is going) that is calculated and being able to load that in to working memory and have constraint based node evaluations would be a very nice and attractive feature. I would suggest as a start a basic content equals (on elements it would match against text content and on attributes it would match against the node value) as well as a basic check for exists based on given xpath. Potential syntax: Fact( xml.xpath("/document//fragment[@id='myid']")) // Checks if the xpath exists in the property xml or Fact( xml.xpath("/document//fragment[@id='myid']") == "myvalue") // Checks if the text content of the fragment with the given id is "myvalue" or Fact( xml.xpath("/document//fragment[@id='myid']/@attr1") == "myattr") // Checks if the node value of the attribute attr1 in the given fragment is "myattr" with the property xml having been defined in the fact. I would suggest implementing this using the latest DOM stuff that has been recently released with xerces 2.9 and up as it has a very fast and efficient xpath evaluator. If you would like I think I can draw up some examples, however I don't think I know enough about drools core code to write this feature myself yet, maybe with some help. Also this constraint module may need a new interface for configuring the size limit (or other constraint) around when to load the xml into working memory. Maybe a annotation based solution in the fact is a good idea (e.g. put an annotation @LoadDOM on xml property in the fact for properties that should be loaded into DOM), or the other option is that the designer has to set the property up as an org.w3c.dom.Document for it to be consider pre-loadable.