Software Engineering

Software Engineering Robbie Clutton

readme.txt Started City University 2001 Did industrial placement with Lloyds TSB 2003-2004 Coding Cobol 74, editing code written before I was born! Graduated Software Engineering BEng 2005 Joined BT graduate scheme

readme.txt SDK to access BT Web Services in .NET C# Worked with customers to build prototypes against BT Web Services RESTful website using Ruby on Rails SIP Application Server to support BT Web Services using Java IVR Web Service using SIP A/S using Java Website using PHP

Unit Testing Tests a unit of code (e.g. a method) Doing the simplest thing that could possibly work Living documentation Allows refactoring Assert upon the correctness of the application

@Test public void testHelloWorld(){ // setup HelloWorld helloWorld = new HelloWorld(); // act String result = helloWorld.sayHello(); // assert assertEquals("Hello", result); } package com.iclutton.seday; public class HelloWorld { public String sayHello() { return language.sayHello(); } }

Benefits unit testing Makes code cleaner Interfaces

package com.iclutton.seday.language; public interface Language { String sayHello(); } package com.iclutton.seday.language; public class English implements Language{ @Override public String sayHello() { return "Hello"; } } package com.iclutton.seday.language; public class French implements Language{ @Override public String sayHello(){ return "Bonjour"; } }

Mocking Useful when you want to ‘mock’ out external dependencies Databases Web services Etc Useful for simulating error conditions and handling

@Test public void testHelloWorldWithMock(){ // setup English english = mock(English. class); when(english.sayHello()).thenReturn("Alright"); HelloWorld helloWorld = new HelloWorld(); helloWorld.setLanguage(english); // act String result = helloWorld.sayHello(); // assert assertEquals("Alright", result); verify(english).sayHello(); } @Test(expected=IllegalStateException. class) public void testHelloWorldWithMockException(){ // setup English english = mock(English. class); when(english.sayHello()).thenThrow( new RuntimeException()); HelloWorld helloWorld = new HelloWorld(); helloWorld.setLanguage(english); // act helloWorld.sayHello(); // assert - see exception annotation }

Dependency Injection We’ve already seen dependency injection Now let’s look at Spring, which supports Reduces complexities of using interfaces Great way to configure applications Promotes the use of singletons Improves testability

<bean id="language" class="com.iclutton.seday.language.English"/> <bean id="hello" class="com.iclutton.seday.HelloWorld"> <property name="language" ref="language"/> </bean> @Test public void testSpring(){ // setup ApplicationContext applicationContext = new ClassPathXmlApplicationContext("applicationContext.xml"); HelloWorld helloWorld = (HelloWorld)applicationContext.getBean("hello"); // act String result = helloWorld.sayHello(); // assert assertEquals("Hello", result); }

Build Scripts Manual processes are more error prone Build scripts bring consistency and automation There are many varieties Ant (Java) nAnt (.NET) Make (C/C++) Rake (Ruby) etc

Property Driven Builds Useful when more that one person becomes involved Or deploying to different environments

Automating the Build Continuous Integration

Logging Until you support an application you’ve built you will never know the value of logging

# Root category log4j.rootLogger=DEBUG, stdout log4j.logger.com.iclutton.seday=DEBUG # CONSOLE log4j.appender.stdout.Threshold=DEBUG log4j.appender.stdout=org.apache.log4j.ConsoleAppender log4j.appender.stdout.layout=org.apache.log4j.PatternLayout log4j.appender.stdout.layout.ConversionPattern=%d %X{stackname}[%t] %-5p [%C {1}.%M() %L] - %m%n 2008-11-18 18:06:39,953 [main] DEBUG [AbstractAutowireCapableBeanFactory$1.run() 411] - Finished creating instance of bean 'hello' 2008-11-18 18:06:39,953 [main] DEBUG [AbstractApplicationContext.publishEvent() 273] - Publishing event in context [org.springframework.context.support.ClassPathXmlApplicationContext@1e845c2]: org.springframework.context.event.ContextRefreshedEvent[source=org.springframework.context.support.ClassPathXmlApplicationContext@1e845c2: display name [org.springframework.context.support.ClassPathXmlApplicationContext@1e845c2]; startup date [Tue Nov 18 18:06:39 GMT 2008]; root of context hierarchy] 2008-11-18 18:06:39,953 [main] DEBUG [AbstractBeanFactory.doGetBean() 214] - Returning cached instance of singleton bean 'hello'

Software Engineering

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