Drools: storing rules in database

Question

Currently I store all rules files on the file system (there are lots of versions of them) and load the different versions of them into memory at startup. I would like to change to storing my drools files in a database and was wondering if there is any solution or addon to Drools which facilitates this or should I craft my own?

Thanks.

Answer 1

Yes, it can be done. All you need is the ability to get InputStream.In my case I use my own JPA class RulePackage to persist rule source as byte[], but you could use direct JDBC connection to access BLOB/CLOB fields in your DB schema. Important thing is to save also type of stored rule source, it will be needed when building rule packages:

switch(rulePackage.getRuleSourceType()) {
  case DRL:
    kbuilder.add( ResourceFactory.newByteArrayResource(rulePackage.getSource()), ResourceType.DRL);
    break;
  case EXCEL:
    kbuilder.add( ResourceFactory.newByteArrayResource(rulePackage.getSource()), ResourceType.DTABLE, excelConfig);
    break;
  case CSV:
    kbuilder.add( ResourceFactory.newByteArrayResource(rulePackage.getSource()), ResourceType.DTABLE, csvConfig);
    break;
  default:
    throw new Exception("Rule package '" + rulePackage.getName() + "' has unknown type");
}

You could consider using newInputStreamResource method if more applicable in your case:

   case DRL:
    kbuilder.add( ResourceFactory.newInputStreamResource(new StringInputStream(myDrlAsString)), ResourceType.DRL);
    break;

or

   case DRL:
    kbuilder.add( ResourceFactory.newInputStreamResource(new ByteArrayInputStream(myDrlAsByteArr)), ResourceType.DRL);
    break;

Something like that.

Answer 2

Yes you can do it by creating rule packages(.pkg files). This is the compiled/binary form of textual rules.

you can specify the name of the package file while creating the knowledgeBuilder and also how frequently the rules should be updated (say 30 seconds).

Use Guvnor to convert the textual rules to .pkg files. keep this file in a folder where the application can access it.

Please revert if you need code samples.