Automatic Java Refactoring

The relevance of code refactoring and our journey to develop a tool for automatic Java refactoring, jSparrow.

Transcript

1. A journey to automatic Java refactoring Software Quality Days 2019 Martin Huter & Ardit Ymeri A journey to automatic Java refactoring (and jSparrow)
2. A journey to automatic Java refactoring Who are we? Slide 2
3. A journey to automatic Java refactoring Agenda ▪ Refactoring ▪ Software aiding the refactoring process ▪ Creating an automatic refactoring tool Slide 3
4. A journey to automatic Java refactoring Management: Do we really need that? Refactoring Slide 4
5. A journey to automatic Java refactoring What is Refactoring Slide 5 ▪ Changing the code and keeping functionality ▪ Reasons include ▪ Improve readability ▪ Reduce complexity ▪ Improve maintainability ▪ Improve internal architecture ▪ Improve performance ▪ Improve security ▪ Parallelization
6. A journey to automatic Java refactoring Typical Problems ▪ Design and code structure ▪ Lack of Cohesion ▪ Tight Coupling ▪ Repeated Code ▪ Spaghetti Code ▪ Lack of Performance ▪ Lack of Tests ▪ Security Issues Slide 6
7. A journey to automatic Java refactoring Human Approach ▪ Define a goal ▪ Understand the code base ▪ Set up a safety net - Tests! ▪ Refactor ▪ Go with baby steps ▪ Test ▪ Does everything still work? ▪ Repeat Slide 7 Refactor Test
8. A journey to automatic Java refactoring Preserving Functionality ▪ Testing helps - but never guarantees. ▪ Program Equivalence ▪ Do programs P and Q terminate on the same state when starting on the same one? ▪ Reducible to the Halting Problem. ▪ Undecidable!!! ▪ All nontrivial semantic properties are undecidable Rice’s Theorem ▪ The good news: Undecidable only in general! ▪ Show correctness for specific cases ▪ Trivial properties are decidable. Slide 8
9. A journey to automatic Java refactoring Using Functional Interfaces Slide 9 SwingUtilities.invokeLater(new Runnable() { @Override public void run() { passwordField.requestFocusInWindow(); passwordField.requestFocus(); } }); SwingUtilities.invokeLater(() -> { passwordField.requestFocusInWindow(); passwordField.requestFocus(); });
10. A journey to automatic Java refactoring Using Standard Outputs Slide 10 System.err.println(e.getMessage()); logger.error(e.getMessage()); e.printStackTrace(); logger.error(e.getMessage(), e);
11. A journey to automatic Java refactoring Cognitive Complexity Slide 11 public void remapIds() { Attribute idAttribute = getAttributes(); if (idAttribute != null) { // very long code … } } public void remapIds() { Attribute idAttribute = getAttributes(); if (idAttribute == null) { return; } // very long code … }
12. A journey to automatic Java refactoring Other Code Smells Slide 12 ▪ Methods should not be empty ▪ Deprecated code should be removed ▪ Sections of code should not be commented out @Deprecated public static void doSomething(Object changeMe) { // throw new UnsupportedOperationException(); }
13. A journey to automatic Java refactoring There is Software that might help Help me? Slide 13
14. A journey to automatic Java refactoring Assessing Technical Debt Slide 14 ▪ Existing Solutions ▪ Integration in development process ▪ Reporting technical debt ▪ Evaluating efforts
15. A journey to automatic Java refactoring Addressing Technical Debt Common scenarios for 100k lines ▪ 10s Thousands issues ▪ Hundreds working days Addressing by: ▪ Avoid creating more debt ▪ Continuously removing debt ▪ Automatically resolving issues Slide 15
16. A journey to automatic Java refactoring Resolving Automatically ▪ Spotting issues ▪ Generating refactored code ▪ Avoiding Conflicts ▪ Preserving Functionality ▪ Test automation ▪ Preserving Comments Slide 16
17. A journey to automatic Java refactoring From Spotting to fixing Can I automate that? Slide 17
18. A journey to automatic Java refactoring Change source with AST Slide 18 1 Parsing source to AST First you need a tool that w ill parse your source code like a com piler 2 M anipulating AST Use the resulting AST to adopt the code and apply fixes 3 Assure syntax still valid Verify changes result in a valid source code 4 W riting Changes Apply the changes to the source file and replace it
19. A journey to automatic Java refactoring What framework to use? Slide 19 Java Grammar Java Compiler Advantages of the Framework • Open source • Integrated within Eclipse IDE 1 Eclipse JDT • Open source • Integrated within Intellij IDE 2 Javaparser.org • Mostly independent • Building a lot from scratch 3 Antlr 4
20. A journey to automatic Java refactoring jSparrow Slide 20 Eclipse JDT Eclipse Plugin GitHub App Maven Plugin
21. A journey to automatic Java refactoring Automatic Refactoring • Pros + Save time + Reduce debt + Set standards + Integration in development process + Improve coding habits • Cons - Technical restrictions Slide 21
22. A journey to automatic Java refactoring jSparrow Features ▪ 53 Rules and growing ▪ Custom rule profiles ▪ Portable between platforms ▪ Built-in review functionality Slide 22
23. A journey to automatic Java refactoring The end ▪ Thanks for your time, we now got some time left to discuss questions. ▪ You can also visit us at our booth at number 13 Slide 23