Spring Web MVC Lab

Learning Goals

• Practice creating a web application using the Spring Framework.
• Create a @RestController class.
• Create a @Service class.
• Use Postman as an API Client tool to test.

Instructions

Create a simple web application using the Spring Framework to perform simple calculator operations between two numbers.

Follow the given instructions and tips:

• Create a CalculatorController class. This will be the controller class.
  • The controller will need to have the following methods:
    • add
    • subtract
    • multiply
    • divide
  • Each of the methods above should take in two double variables as request parameters.
  • Each of the methods above should return a Double.
  • Each of these methods will use the @GetMapping annotation with the method name as the path (i.e., "/add" will be the route for the add() method).
    • Since each of these methods will take in two parameters, the full URL might look like: http://localhost:8080/add?x=8&y=4 where x and y are the request parameters.
• Create a CalculatorService class. This will be where we place the business logic.
  • The service will need to have the following methods:
    • sum
    • difference
    • product
    • quotient
  • Each of the methods above should take in two double variables as parameters and return a Double.
  • For the subtract() and divide() methods, the first number argument will be the minuend or the dividend respectfully.
    • If the first parameter in a subtraction method is 5, then 5 will be the number we subtract from.
    • If the first parameter in a division method is 5, then 5 will be the number that is being divided.
  • Remember, anything divided by 0 is not a number. Print an error to the console and return null when 0 is given as divisor (second number).
  • Add the service to the controller class as we saw in the Service Class lesson.
    • Add a private final reference to the CalculatorService class to the controller class.
    • Add an @Autowired constructor to the controller class.
• Suggestion: Start by implementing the add() and sum() methods in the controller and the service classes respectively. Once that is working, then add the other methods one at a time.
• Use the SpringMod1MvcLabApplication class to run the application.
• Use Postman to test the application.

Project Structure

The Spring Boot project has already been initialized for you. Consider the following project structure:

├── CONTRIBUTING.md
├── HELP.md
├── LICENSE.md
├── mvnw
├── mvnw.cmd
├── pom.xml
├── README.md
└── src
    ├── main
    │   ├── java
    │   │   └── com
    │   │       └── example
    │   │           └── springmod1mvclab
    │   │               ├── SpringMod1MvcLabApplication.java
    │   │               ├── controller
    │   │               │   └── CalculatorController.java
    │   │               └── service
    │   │                   └── CalculatorService.java
    │   └── resources
    │       ├── application.properties
    │       ├── static
    │       └── templates
    └── test
        └── java
            └── org
                └── example
                    └── springmod1mvclab
                        └── SpringMod1MvcLabApplication.java

Example Output

Consider the example outputs:

Addition

Request URL: http://localhost:8080/add?x=8.0&y=4.0

Subtraction

Request URL: http://localhost:8080/subtract?x=8.0&y=4.0

Multiplication

Request URL: http://localhost:8080/multiply?x=8.0&y=4.0

Division

Request URL: http://localhost:8080/divide?x=8.0&y=4.0

Request URL: http://localhost:8080/divide?x=8&y=0

Note that request above will attempt to divide by 0; which should return null since anything divided by 0 is not a number.