Beans.LearnerLab

Bean Flavored Learner Lab

• Objective - to register a Classroom bean which mediates a composite Students and Instructors bean reference.
• Purpose - to demonstrate the use of
  • Bean registration
  • Dependency Injection
  • IOC Container
  • AnnotationConfigApplicationContext
  • Annotations
    • @Bean
    • @DependsOn
    • @Autowired
    • @PostConstruct
    • @Config
    • @SpringBootTest
    • @Qualifier

Developmental Notes

• Do NOT clone this repository until completing Part 0.0
• You may structure this project and the packaging how you please, however keep in mind that @Configuration scans from current directory down.
• Until Part 10, this project is nearly identical to the LearnerLab completed in the past.

Part 0.0 - Generating Project

• Navigate to start.spring.io
• In the Search for Dependencies input box search for
  • DevTools
  • Web
• Select Generate Project
• After the project has completed downloading, navigate to the download directory and unzip the project folder.
• At the root directory of the project, clone this repository.
• Move all files from the demo project generated by start.spring.io, into the newly cloned learnerlab folder.
• Open the project via its pom.xml from IntelliJ > File > Open
  • Be sure to Open as Project when prompted

Part 1.0 - Create Person Class

• Create a Person class.
  • The class should declare a final field named id of type long.
  • The class should declare a field named name of type String.
    
  • Person constructor should have a parameter of type Long id, String name which sets each of the fields to their respective value.
  • The class should define a getId() method which returns the Person object's id field.
  • The class should define a getName() method which returns the Person object's name field.
  • The class should define a setName() method which sets the Person object's name field.

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Part 2.0 - Create Learner Interface

• Create a Learner interface.
  • Learner should declare one method signature:
    • Method name: learn
    • Method parameters: double numberOfHours
    • Method return-type: void

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Part 3.0 - Create Student Class

• Create a Student class such that:
  • Student is a subclass of Person
  • Student implements the Learner interface
  • Student should have an instance variable totalStudyTime of type double
  • Student should have a concrete implementation of the learn method which increments the totalStudyTime variable by the specified numberOfHours argument.
  • Student should have a getTotalStudyTime() method which returns the totalStudyTime instance variable.

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Part 4.0 - Create Teacher Interface

• Create a Teacher interface.

  • Teacher should declare a teach method signature:

    • Method name: teach
    • Method parameters:
      • Learner learner
      • double numberOfHours
    • Method return-type: void

  • Teacher should declare a lecture method signature:

    • Method name: lecture
    • Method parameters:
      • Iterable<? extends Learner> learners
      • double numberOfHours
    • Method return-type: void
      

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Part 5.0 - Create Instructor Class

• Create an Instructor class such that:
  • Instructor is a subclass of Person
  • Instructor implements the Teacher interface
  • Instructor should have a concrete implementation of the teach method which invokes the learn method on the specified Learner object.
  • Instructor should have a concrete implementation of the lecture method which invokes the learn method on each of the elements in the specified array of Learner objects.
    • numberOfHours should be evenly split amongst the learners.
      • double numberOfHoursPerLearner = numberOfHours / learners.length;

Part 6.0 - Create People

• Create an abstract People class
  • The class signature should be parameterized with PersonType such that PersonType is a sub class of Person.
  • The class should implement Iterable of type PersonType.
  • Upon construction People should consume a List of PersonType and set it to a respective personList field.
  • The class should define a constructor which consumes a variable number of PersonType objects and sets the personList field respectively.
  • The class should define a method named add which adds a PersonType to the personList.
  • The class should define a method named remove which removes a PersonType from the personList.
  • The class should define a method named size which returns the size of personList.
  • The class should define a method named clear which clears our personList field.
  • The class should define a method named addAll which adds an Iterable of PersonType objects to the composite personList.
    • This method will NOT take an argument of Collection<PersonType>
  • The class should define a method named findById which makes use of a long id parameter to return a PersonType object with the respective id field.
  • The class should define a method named findAll which returns the composite personList.

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Part 7.0 - Create Students

• Create a Students class.
  • The class should be a subclass of People of parameterized type Student.
  • The class should consume a variable number of Student objects upon construction and pass them to the super constructor.

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Part 8.0 - Create Instructors

• Create a Instructors class.
  • The class should be a subclass of People of parameterized type Instructor.
  • The class should consume a variable number of Instructor objects upon construction and pass them to the super constructor.

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Part 9.0 - Create Classroom

• Create a Classroom class.
  • The class should consume and set composite reference to an Instructors and Students object upon construction
  • The class should define a method hostLecture which makes use of a Teacher teacher, double numberOfHours parameter to host a lecture to the composite personList field in the students reference.
    

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Part 10.0 - Creating Configuration classes

• Each of the following Config classes should have a class-signature annotation of @Configuration
  • this annotation tells spring to scan for @Bean definitions within the scope of the class, and register them to the IOC Container for Inject and Autowire use later.
• Classroom should define getters for each of its fields.

Developmental Notes

• @Autowired

  • injects bean by type
  • can be used alone.
  • If is used alone, it will be wired by type
  • If more than one bean of same type are declared in the container @Autowired does not know which beans to use for injection.

• @Qualifier

  • injects bean by specified name
  • supports fields, setter, constructors and multi-argument methods injection
  • together with @Autowired, clarifies which beans to be wired by specifying the bean name (wired by name)

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Part 10.1 - Create StudentConfig

• Note: The creation of this class will demonstrate an implementation of bean registration in Spring.
• The class should define a method named currentStudents() which returns a Students representative of the current cohort of students.
  • the method should be annotated with @Bean(name = "students")
    • this ensures the Spring container registers the bean with the respective name.
    • a @Bean whose name attribute is not specified defaults to the name of the method it is annotating.
• The class should define a bean named previousStudents() which returns a Students representative of the previous cohort of students.
  

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Part 10.2 - Create InstructorsConfig

• The class should define a bean named tcUsaInstructors() which returns an Instructors representative of the Tech Connect USA instructors.
• The class should define a bean named tcUkInstructors() which returns an Instructors representative of the Tech Connect UK instructors.
• The class should define a bean named instructors which returns all Instructors employed at ZipCodeWilmington
  • annotate this bean with @Primary
    • this ensures Spring will inject this bean in the case that an Autowire annotation is not supplied with a Qualifier annotation

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Part 10.3 - Create ClassroomConfig

• The class should define a bean named currentCohort() which returns a Classroom object whose dependencies are instructors and students
• The class should define a bean named previousCohort() which returns an Classroom object whose dependencies are instructors and previousStudents
• Note: it is sometimes useful (although not always necessary) to use the @DependsOn annotation to help the Spring framework and other readers of the code to understand what order beans should be executed.
  • @DependsOn({"instructors", "students"})
    

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Part 11.0 - Test Config classes

• Each of the following Test classes should be annotated with
  • @RunWith(SpringRunner.class)
    • enforces which strategy junit should use to run tests
  • @SpringBootTest
    • indicates that this class is a Spring Boot test class
    • provides support to scan for a ContextConfiguration that tells the test class how to load the ApplicationContext.
    • If no ContextConfiguration classes are specified as a parameter to the @SpringBootTest annotation, the default behavior is to load the ApplicationContext by scanning for a @SpringBootConfiguration annotation on a class in the package root.
• Each bean can be injected into the class scope using @Autowired along with @Qualifier(name = "beanname")

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Part 11.1 - Test StudentConfig Class

• Create a TestStudentConfig class in the test package.
• The class should ensure that each Bean in the StudentConfig class is configured as expected.
• Tip: You can use the toString method to get a representation of the aggregate state of any People object.

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Part 11.2 - Test InstructorConfig Class

• Create a TestInstructorConfig class in the test package.
• The class should ensure that each Bean in the TestInstructorConfig class is configured as expected.

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Part 11.3 - Test ClassroomConfig Class

• Create a TestClassroomConfig class in the test package.
• The class should ensure that each Bean in the TestClassroomConfig class is configured as expected.

Part 11.0 - Using @Component

• Annotating a class signature with @Component allows Spring to register the class as a Bean implicitly.

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Part 11.1 - Create Alumni Class

• Create an Alumni component which autowires Students of the previous cohort and Instructors
• Create an executeBootcamp method which teaches each Student in the composite Students a totalNumberOfHours of 1200.
  • Annotate this method with @PostConstruct
    • denotes that this method must be executed before the class is put into an IoC container
• Create a getter for each of the fields.

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Part 11.2 - Test Alumni Class

• Write a test class which ensures that each Student in the Alumni class has been taught 1200 hours upon injection of the Alumni dependency.

• Ensure the numberOfHoursTaught has been evenly distributed amongst each of the instructors.

• Tip: How to derive numberOfHoursTaught dynamically

  int numberOfInstructors = instructors.size();
  int numberOfStudents = students.size();
  double numberOfHoursToTeachEachStudent = 1200;
  double numberOfHoursToTeach = numberOfHoursToTeachEachStudent * numberOfStudents;
  double numberOfHoursPerInstructor = numberOfHoursToTeach / numberOfInstructors;