drools-eclipse/org.drools.eclipse/src/main/java/org/drools/eclipse/editors/completion/DSLTree.java
protected BufferedReader openDSLFile(String filename) {
        try {
            FileReader reader = new FileReader(filename);
            BufferedReader breader = new BufferedReader(reader);
            return breader;
        } catch (IOException e) {
            e.printStackTrace();
            return null;
        }
    }
protected BufferedReader openDSLFile(String filename) {
        try {
            FileReader reader = new FileReader(filename);
            BufferedReader breader = new BufferedReader(reader);
            return breader;
        } catch (IOException e) {
            e.printStackTrace();
            return null;
        }
    }
method will create a BufferedReader to read the file.
@param filename
@return