7. Software Development

Size: px

Start display at page:

Download "7. Software Development"

Alfred Sanders
5 years ago
Views:

1 7. Software Development Prof. Dr. Dirk Riehle, M.B.A. Friedrich Alexander-University Erlangen-Nürnberg Version of Agile Methods by Dirk Riehle is licensed under a Creative Commons Attribution- ShareAlike 3.0 Unported License. Based on a work at dirkriehle.com.

4 Content of Software Development Chapter 1. General Software development 2. Principles General principles Coding guidelines Collective code ownership Pair programming 3. Programming Refactoring Test-first programming Test-driven Development 4. Team Collaboration Configuration management Build management Continuous integration 2012 Dirk Riehle - All Rights Reserved 4

5 Traditional vs. Agile Software Development Traditional SD Upfront design Module-oriented Separated from QA Agile Methods SD Emergent design Feature-oriented Joined with QA 2012 Dirk Riehle - All Rights Reserved 5

10 Coding Guidelines (Practice) Definition Coding guidelines (or rules) are a set of conventions that determine desired naming, formating and structuring of source code and related artifacts. Properties Eases reading source code Eases navigating project Are typically mandatory Java Guidelines [S1] File Names File Organization Indentation Comments Declarations Statements White Space Naming Conventions Programming Practices 2012 Dirk Riehle - All Rights Reserved 10

11 Example Coding Guidelines Beginning Comments All source files should begin with a c-style comment that lists the class name, version information, date, and copyright notice: /* * Classname * * Version information * * Date * * Copyright notice */ 4.2 Wrapping Lines When an expression will not fit on a single line, break it according to these general principles: Break after a comma. Break before an operator. Prefer higher-level breaks to lower-level breaks Placement Put declarations only at the beginning of blocks. (A block is any code surrounded by curly braces "{" and "".) Don't wait to declare variables until their first use; it can confuse the unwary programmer and hamper code portability within the scope. void mymethod() { int int1 = 0; // beginning of method block if (condition) { int int2 = 0; // beginning of "if" block Simple Statements Each line should contain at most one statement. Example: argv++; // Correct argc--; // Correct argv++; argc--; // AVOID! 2012 Dirk Riehle - All Rights Reserved 11

12 Naming Conventions package org.wahlzeit.model; import java.sql.*; import org.wahlzeit.services.*; public class PhotoFactory {... public Photo createphoto() { return new Photo(); public Photo createphoto(photoid id) { return new Photo(id); public Photo createphoto(resultset rs) throws SQLException { return new Photo(rs); public PhotoFilter createphotofilter() { return new PhotoFilter(); public PhotoTagCollector createphototagcollector() { return new PhotoTagCollector(); 2012 Dirk Riehle - All Rights Reserved 12

13 Query Method Types [R1] Definition A query method (a.k.a. accessing method) is a method that returns some information about the object being queried. It does not change the object's state. Example A comparison method is a query method that compares two objects and returns a value that tells you which object is "greater" or "lesser" than the other one according to an ordering criterion. Query Method Types Get method (getter) Default value method Boolean query method Comparison method Conversion method Dirk Riehle - All Rights Reserved 13

14 Mutation Method Types Definition A mutation method (a.k.a. command method) is a method that changes the state of the object in a single well-defined way. Example An initialization method is a mutation method that sets some or all fields of an object to an initial value. Mutation Method Types Set method (setter) Command method Initialization method Finalization method Configuration method Constructor Dirk Riehle - All Rights Reserved 14

15 Helper Method Types Definition A helper method (a.k.a. utility method) is a method that performs a support task for the calling object. A helper method does not change the object's state, but only performs operations on the method arguments. Example An assertion method is a helper method that checks whether a certain condition holds. If the condition holds, it returns silently. If it does not hold, an appropriate exception is thrown. Helper Method Types Creation method Factory method Cloning method Trading method Conversion method Assertion method Logging method Dirk Riehle - All Rights Reserved 15

16 Design Pattern Conventions public class PhotoFactory { private static PhotoFactory instance = null; public static synchronized PhotoFactory getinstance() { if (instance == null) { SysLog.logInfo("Setting generic PhotoFactory"); setinstance(new PhotoFactory()); return instance; protected static synchronized void setinstance(photofactory photofactory) { if (instance!= null) { throw new IllegalStateException("Attempting to initalize again"); instance = photofactory; public static void initialize() { getinstance(); // drops result due to getinstance() side-effects protected PhotoFactory() { // do nothing Dirk Riehle - All Rights Reserved 16

17 Design Patterns [G1] Definition A design pattern is proven solution to a recurring design problem in a defined context. A solution becomes a pattern after three known examples. Example GoF Design Patterns Creational Patterns: Abstract Factory, Builder, Factory Method, Prototype, Singleton Structural Patterns: Adapter, Composite, Bridge, Decorator, Facade, Flyweight, Proxy Behavioral Patterns: Chain of Responsibility, Command, Interpreter, Iterator, Mediator, Memento, Observer, State, Strategy, Template Method, Visitor More Design Patterns Null Object, Type Object, Role Object, Serializer, Product Trader, Dirk Riehle - All Rights Reserved 17

18 Collective Code Ownership (Practice) Definition Source code (and other artifacts) is collectively owned (collective code ownership) if every member of the collective has full read and write access to the code. The opposite of collective code ownership is individual code ownership. Properties Every member of the collective Cares about the architecture Cares about clean code Ensuring high quality Every single author can Implement a feature end-to-end Finish a refactoring Fix a bug 2012 Dirk Riehle - All Rights Reserved 18

20 Refactoring (Practice) Definition A refactoring is a behavior-preserving transformation of existing source code. It is a change made to the internal structure of software to make it easier to understand and cheaper to modify without changing its observable behavior. History Defined by Opdyke [O1] Popularized by Fowler [F1] Properties Change structure of code Without changing behavior Focus on non-functional features Within range of specification Are defined techniques Are typically language specific Are ideally supported by IDEs UIUC Refactoring Browser Eclipse JDT 2012 Dirk Riehle - All Rights Reserved 20

21 Benefits of Well-Factored Code [1] 1. Maintainability (Easier to understand) 2. Extensibility (Easier to adapt and evolve) 3. Predictability (Improves planning ability) [1] Well-factored code is code where no more refactoring is possible or reasonable Dirk Riehle - All Rights Reserved 21

22 Extract-Method Refactoring (Example) 1 / 2 public class PhotoManager extends ObjectManager { protected Map<PhotoId, Photo> allphotos = new HashMap<PhotoId, Photo>(); public void addphoto(photo photo) { PhotoId id = photo.getid(); assertisnewphoto(id); allphotos.put(id, photo);... public Photo getphotofromid(photoid id) { Photo result = dogetphotofromid(id); if (result == null) {... if (result!= null) { allphotos.put(id, result) return result; public Set<Photo> findphotosbyowner(string ownername) { Set<Photo> r = new HashSet<Photo>();... for (Iterator<Photo> i=r.iterator(); i.hasnext();) { Photo photo = i.next(); allphotos.put(photo.getid(), photo); return r; 2012 Dirk Riehle - All Rights Reserved 22

23 Extract-Method Refactoring (Example) 2 / 2 public class PhotoManager extends ObjectManager { public void addphoto(photo photo) {... doaddphoto(photo); public Photo getphotofromid(photoid id) {... doaddphoto(photo); public Set<Photo> findphotosbyowner(string ownername) {... for (Iterator<Photo> i=r.iterator(); i.hasnext(); ) { doaddphoto(i.next()); protected void doaddphoto(photo myphoto) { allphotos.put(myphoto.getid(), myphoto); Dirk Riehle - All Rights Reserved 23

27 When to Refactor? (Code Smells) 2 / 3 Duplicated Code Extract Method Pull Up Field Form Template Method Substitute Algorithm Extract Class Long Method Extract Method Decompose Conditional Large Class Extract Class Extract Subclass Extract Interface More Smells Long Parameter List Divergent Change Data Clumps Dirk Riehle - All Rights Reserved 27

30 Refactoring Process 2 / 2 Refactoring Process Can get complex May be series of refactorings Switch Statement 1. Extract Method 2. Move Method 3. Replace Type Code with Subclass or with State / Strategy 4. Replace Conditional... with Polymorphism 2012 Dirk Riehle - All Rights Reserved 30

32 Video Lessons Explanation Technical Debt is a Metaphor Taking on debt can speed up Use of Metaphor Speaks well to manager Certainly in financial services May be justified to learn faster But you have to pay up later If you don't you'll slow down Paying up means refactoring For this, still don't write poor code 2012 Dirk Riehle - All Rights Reserved 32

34 Configuration Management (Practice) Definition Configuration management is the process of managing all relevant artifacts that make up a software product and tracking all relevant changes to them. A configuration management system (CMS) is a software product that serves as the record keeper for all artifacts tracked by configuration management. A configuration management system embodies a specific collaboration model and thus needs to be compatible with your desired development process. Properties Used to define specific states Used to track configurations Example Systems CVS, Subversion (svn) git, Mercurial (hg) Clearcase, Perforce 2012 Dirk Riehle - All Rights Reserved 34

35 Traditional Configuration Management Definition Has central repository Commits effect team directly TM Tracks small changes centrally Example Tools CVS, svn Commit Code Repo 2012 Dirk Riehle - All Rights Reserved 35

36 Distributed Configuration Management Definition Has local and team repository Commits effect local repo first TM Team sees semantic progress Example Tools git, hg Commit Local Repo Push Pull Team Repo 2012 Dirk Riehle - All Rights Reserved 36

37 Versions and Releases Version Identifies configuration Is codified as number x.y.z Release Is version provided to customer Numbering System Major = new functionality Minor = small new functionality Micro = small change, bug fix Label = typically internal only Typically has major increment major minor micro label RC x/m x alpha x/beta x build id (date) 2012 Dirk Riehle - All Rights Reserved 37

38 Branches and the Main-Line Branch A branch is a copy of the code being developed further independently of the main-line A branch is used to stabilize the main-line for public release and develops slowly only A branch ultimately dies Main-Line The main-line is the branch where on-going new-feature development takes place There is only one main-line and it never dies as long as the product lives on A.k.a. trunk, head, x 1.7.x 2.1.x main-line (or: trunk) 2012 Dirk Riehle - All Rights Reserved 38

39 backport backport backport backport Configuration Management (Linux Example) new features bug fix commercial features new feat. bug fix new feat. bug fix new feat. bug fix EOL commercial features EOL 2012 Dirk Riehle - All Rights Reserved 39

40 Build Process and Management Build Process The build process is the defined and (ideally automated) process of deriving an installable product from its source artifacts. Every project needs a defined build process; these days, it is well supported by tools, for example, ant, maven, etc. Build Manager Builds product from repository Ideally regularly, automated Identifies build problems Tracks down causes of failure Defines standard environment Supports developers with setup Defines commit rules For example, no executables Manages test-first data 2012 Dirk Riehle - All Rights Reserved 40

41 Developer Responsibilities Only work in defined standardized environment This ensures no subtle differences to central build process Only commit / push code that compiles and works Breaking the build through non-compiling code hurts team Only commit / push code that passes all the tests Failing tests quickly degenerate system (hard to catch-up) 2012 Dirk Riehle - All Rights Reserved 41

42 Quiz: Agile Software Development 1. You need a method to create a new photo. Which name is best? PhotoFactory.make() PhotoFactory.newPhoto() PhotoFactory.createPhoto() PhotoFactory.createNewPhoto() 2. A file may have many authors. Should the names of these authors be listed in the file's header? Yes No 3. It is the last workday of the week and you want to go home. Should you always commit to the team repository? Yes No 2012 Dirk Riehle - All Rights Reserved 42

8. Quality Assurance

8. Quality Assurance Prof. Dr. Dirk Riehle, M.B.A. Friedrich Alexander-University Erlangen-Nürnberg Version of 22.03.2012 Agile Methods by Dirk Riehle is licensed under a Creative Commons Attribution-