Software modularity and reuse Paulo Borba Informatics Center Federal University of Pernambuco

[email protected] ◈ twitter.com/pauloborba Monday, September 20, 2010

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Components and parametrization

Monday, September 20, 2010

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Different devices, 15 to 60 different applications…

Different clients, different products

http://www.androidauthority.com Monday, September 20, 2010

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Reuse problems

Monday, September 20, 2010

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Modularity problems

Monday, September 20, 2010

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Refactoring problematic component

Test 1 Test 2

improved component

Test 1 Test 2

...

...

Monday, September 20, 2010

refactoring

Test n

Test n

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Patterns

Monday, September 20, 2010

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Variability patterns (avoiding code duplication in product families) Monday, September 20, 2010

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Template method

http://www.refactoring.com/catalog/formTemplateMethod.html Monday, September 20, 2010

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PDC, bridge variation... class AccountRecord { private AccountRepository accounts;... public void register(Account a) { if (a != null) { String n = a.getNumero(); if (!accounts.exists(n)) { accounts.insert(a); } } } Monday, September 20, 2010

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variation is whole data structure interface AccountRepository { void insert(Account account); Account search(String number); boolean exists(String number); } class AccountArray implements AccountRepository {...} class AccountVector implements AccountRepository {...} Monday, September 20, 2010

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Compare patterns

Monday, September 20, 2010

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But how are variants chosen? Monday, September 20, 2010

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Product family assets Java files, abstract

Java files, concrete

Java files, decision ... new AccountArray ... ...

Makefiles

Monday, September 20, 2010

new AccountVector ...

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Parametrized factory... Java files, abstract

Java files, concrete

Java file, decision ... if (...) {... new AccountArray

...

} else {... new AccountVector

Makefiles

...

} ...

Monday, September 20, 2010

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with property (or XML) file Properties p = new Properties(); p.load(new FileInputStream("repository.prop")); ... if (p.getProperty("ACCOUNT_REP") == 1) { ... } else {...} ...

Monday, September 20, 2010

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Property files as assets Java files, abstract

Java files, concrete

Java file, decision ... if (...) {...} else {...} ...

Property files Makefiles

ACCOUNT_REP=1 ACCOUNT_REP=2

Monday, September 20, 2010

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Properties parametrize behavior and data Properties p = new Properties(); p.load(new FileInputStream("device_screen.prop")); ... draw(p.getProperty("SCREEN_WIDTH"),50); ...

Monday, September 20, 2010

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Compare mechanisms

Monday, September 20, 2010

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Analyzing subtype polymorphism • Variation point: supertypes (methods) in the program text • Variation: subtypes (including methods and fields) • Binding time: execution time, based on makefile choice (compilation/build time) • Mechanism: subtype definition, variation modularization Monday, September 20, 2010

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Analyzing file parametrization • Variation point: expressions in the program text, and commands too (with conditionals) • Variation: constants and values, commands • Binding time: execution time, based on makefile choice (build time) • Mechanism: value instantiation, decision

Monday, September 20, 2010

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Decision mechanisms for subtype polymorphism • Makefiles (different mains or factories)

developer

• Makefiles + property_files + conditionals • Makefiles + property_files + reflection • Input + conditionals

user

• Input + reflection

Monday, September 20, 2010

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Environment decision, with dependency injection... class AccountRecord { private AccountRepository accounts; void setRepository(AccountRepository r) { accounts = r; } ... Not a developer decision, nor } a user decision!

Monday, September 20, 2010

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Components • Improvement over subtype polymorphism and Java packages • not by defining subtypes of abstract classes, but of interfaces • clientship + subtype polymorphism • deployment independence • service location and management • module visibility and versions

Monday, September 20, 2010

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Containers Client

component component

XML

Java Java Java

component component

component

Monday, September 20, 2010

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Extending Eclipse... Monday, September 20, 2010

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and allowing extensions Monday, September 20, 2010

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Acessing variations ep = Platform...getExtensionPoint("ELP_EP.languageSet"); IExtension[] extensions = ep.getExtensions(); for (IExtension e : extensions) { configs = e.getConfigurationElements(); for (IConfigurationElement c : configs) { if (c.getName().equals("language")) { ...new Path(c.getAttribute("languageFile")); } } }

Monday, September 20, 2010

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Components in Spring

http://www.developer.com/img/articles/2005/04/13/List108.gif Monday, September 20, 2010

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When and where to use this?

Monday, September 20, 2010

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Parametrization via parametric polymorphism public class Record { ... public void insert(ComplaintType o) { ... } } ... Record ... Monday, September 20, 2010

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Parametric polymorphism core assets Java file, generic Makefiles

Java files, specific ... Record ... Monday, September 20, 2010

... Record ... 32

Parametrizing data + operations public class Record< ComplaintType extends CodeIdentifiable> { ... public ComplaintType search(int code){ ... } public void insert(ComplaintType o) { ... } interface CodeIdentifiable { } int getCode(); } Monday, September 20, 2010

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Analyzing parametric polymorphism • Variation point: class parameters (types and methods) in the program text • Variation: types (including methods) • Binding time: compilation time, based on makefile choice • Mechanism: type instantiation, variation and “common” code modularization Monday, September 20, 2010

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Black belt parametrization! Monday, September 20, 2010

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Smells good?

functions as parameters

artigos.each{|a| map = {} a.elements.each("DADOS-BASICOS-DO-ARTIGO"){|d| atts = d.attributes map["TITULO-DO-ARTIGO"] = atts["TITULO-DO-ARTIGO"] map["ANO-DO-ARTIGO"] = atts["ANO-DO-ARTIGO"] } a.elements.each("DETALHAMENTO-DO-ARTIGO"){|d| atts = d.attributes map["TITULO-DO-MEIO"] = atts["TITULO-DO-MEIO"] map["VOLUME"] = atts["VOLUME"] map["FASCICULO"] = atts["FASCICULO"] map["PAGINA-INICIAL"] = atts["PAGINA-INICIAL"] map["PAGINA-FINAL"] = atts["PAGINA-FINAL"] } ... Monday, September 20, 2010

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Not only for articles... ... a.elements.each("AUTORES"){|author| map["AUTORES"] = (if map["AUTORES"] then map["AUTORES"] else [] end) + [author.attributes["NOME-PARA-CITACAO"]] } }

Monday, September 20, 2010

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XML structure as parameter artigos.each{|a| map = {} structure = { "DADOS-BASICOS-DO-ARTIGO" => ["TITULO-DO-ARTIGO", "ANO-DO-ARTIGO"], "DETALHAMENTO-DO-ARTIGO" => ["TITULO-DO-MEIO", "VOLUME", "FASCICULO", "PAGINA-INICIAL", "PAGINA-FINAL"], "AUTORES" => ["*", "NOME-PARA-CITACAO"]} }

Monday, September 20, 2010

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Abstracting structure details structure.keys.each {|e| a.elements.each(e) {|d| atts = d.attributes if structure[e].include?("*") then (structure[e] - ["*"]).each {|att| map[e] = (if map[e] then map[e] else [] end) + [atts[att]] } else structure[e].each {|att| map[att] = atts[att] } end } } Monday, September 20, 2010

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Improvement is more often needed than not, so abstract to see it! Monday, September 20, 2010

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Take notes, now! Monday, September 20, 2010

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Components and parametrization

Monday, September 20, 2010

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Software modularity and reuse Paulo Borba Informatics Center Federal University of Pernambuco

[email protected] ◈ twitter.com/pauloborba Monday, September 20, 2010

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