FindBugs OBL_UNSATISFIED_OBLIGATION

I'm trying to find bugs in on of our legacy code using findBugs. In one the methods, findBugs is giving OBL_UNSATISFIED_OBLIGATION error. I have verified that all streams are properly closed. Here is the code snippet:

FileWriter fw = null;
FileReader fr = null;
try { if (!new File(filePath).exists()) { requiredStrings = CommandUtils.invoke(filename); fw = new FileWriter(filePath); fw.write(requiredStrings); } else { StringBuilder sb = new StringBuilder(); fr = new FileReader(filePath); char[] buffer = new char[BLOCK_READ_SIZE]; int bytesRead; while (-1 != (bytesRead = fr.read(buffer, 0, BLOCK_READ_SIZE))) { sb.append(buffer, 0, bytesRead); } requiredStrings = sb.toString(); }
} finally { if (fw != null) { fw.close(); } if (fr != null) { fr.close(); }
}
return requiredStrings;

The error says that Obligation to clean up resurces in not discharged, Path continues at ....line.... Remaining obligations {Reader x 1, Writer x-1}

2 Answers

You have to catch IO exceptions throwed by FileReader and FileWriter when they are closing. You can do that in Java 7 and upper with try with resources

try (FileWriter fw = new FileWriter(filePath); FileReader fr = new FileReader(filePath)) { /*your code here*/ } catch (FileNotFoundException e) { e.printStackTrace(); } catch (IOException e) { e.printStackTrace(); }

Or by the old way

 FileWriter fw = null; FileReader fr = null; try { /*your code here*/ fw = new FileWriter(filePath); /*your code here*/ fr = new FileReader(filePath); /*your code here*/ } catch (FileNotFoundException e) { e.printStackTrace(); } catch (IOException e) { e.printStackTrace(); } finally { try { if (fw != null) { fw.close(); } if (fr != null) { fr.close(); } } catch (IOException e) { e.printStackTrace(); } }
}

In a method, it opens a InputStream for reading, if there is a chance the method quits without closing this InputStream object, FindBugs would complain like fail to clean up java.io.InputStream on checked exception. For example:

void readProperties() throws FooException{ InputStream is= ... PropertyFactory.getInstance().loadXXXFromPropertyStream(is); // it throws FooException is.close(); // maybe never called for a FooException leaving inputstream is open.
}