Why are you trying to read it from your classpath?  As it wasn’t in your classpath when you loaded java doesn’t know about it.

You already have the File object so you can just make a FileReader object from that.


Reader source = new FileReader(drlFile);


Don’t forget to close your reader when you are done with it, ideally in a finally block so that ti gets closed even if there is an IOException while reading from it.


Also you really really really shouldn’t write files into your source directory as it means that running a clean doesn’t work properly, is likely to confuse eclipse and lead to all sorts of other funnies like dynamic files suddenly appearing in your classpath... For unit tests write it to “target/testOutput” or similar.


Hope this helps,



From: rules-users-bounces@lists.jboss.org [mailto:rules-users-bounces@lists.jboss.org] On Behalf Of Fnu Mahalakshmi
Sent: 15 June 2010 22:05
To: 'rules-users@lists.jboss.org'
Subject: [rules-users] Weird error with rule files




When I run my project – I have brl and drl rule files.

When I run it for the first time: I am converting brl to drl files.

I get this error


Exception in thread "main" java.lang.NullPointerException

      at java.io.Reader.<init>(Unknown Source)

      at java.io.InputStreamReader.<init>(Unknown Source)

      at com.org.RuleRunner.loadRuleFile(RuleRunner.java:87)

      at com.org.RuleRunner.loadRules(RuleRunner.java:44)

      at com.org.RuleRunner.runStatelessRules(RuleRunner.java:108)

      at com.org.RulesTest.main(RulesTest.java:40)



But after I run it for the first time and the rule.drl (converted file from brl to drl) exists in my directory – I run it again and then the program runs fine.


So number of .brl files that many number of exceptions(same as above) and then program runs.


Why is this happening?? Should it not create the file and load it into the rulebase?


My code for converting from brl to drl is :


                  BRXMLPersistence read = (BRXMLPersistence) BRXMLPersistence.getInstance();

                  BRDRLPersistence write = (BRDRLPersistence) BRDRLPersistence.getInstance();

                  brl = FileUtils.readFileToString(file);

                System.out.println("File content: " + brl);

                outputDRL = write.marshal(read.unmarshal(brl));

                String drlFilePath = "src/main/rules"+rulesFiles +".drl";

                System.out.println("drlFilePath "+drlFilePath +"rulesFiles "+rulesFiles);

                String path = rulesFiles+".drl";

                System.out.println("path "+path);

                System.out.println("drlfile "+drlFilePath);

                drlFile = new File(drlFilePath);

                FileUtils.writeStringToFile(drlFile, outputDRL);


                Reader source = new InputStreamReader( RuleRunner.class.getResourceAsStream(path) ); // error is here


            }catch (IOException e) {






Any idea why this problem?? Is there some error in my code above????


Please help.

Thank you


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