Cheat Sheet

This cheat sheet contains important takeaways that lead up to section eight.

REST API

Definitions

• API: Mediator between a consumer and a system
• REST API: API that conforms to a set of guidelines.
• JSON: universal format of key-value pairs that all systems can understand.

{
    "name": "Tyrion Lannister",  //JSON STRING
    "phoneNumber": "4515429321",  // JSON STRING
    "age": 40,  // JSON NUMBER
    "height": 1.2,  // JSON NUMBER
    "siblings": [ "Cersei", "Jaime" ], // JSON ARRAY
    "alwaysDrunk": true // JSON BOOLEAN
}

REST Guidelines:

• Resource: piece of data that can be named (Contact, Employee).
• URI: Uniform Resource Identifier – identifies the location of a resource.
• The API defines operations that can manipulate resources:
  • GET: retrieves a resource.
  • POST: creates a resource.
  • PUT: updates a resource.
  • DELETE: deletes a resource.
• The resource is most often serialized into JSON.

Spring Boot REST

• @RESTController:
  • Combines @Controller and @ResponseBody.
• @GetMapping, @PostMapping, @PutMapping, @DeleteMapping: method-level annotations that instrument methods to handle different types of requests.
• @ResponseBody:
  • is capable of serializing a returned Object into JSON.
• @RequestBody
  • is capable of deserializing incoming JSON data into the fields of an object.
• @PathVariable: extracts a variable from the provided path.
• ResponseEntity<Object>:
  • object is serialized into JSON before being sent off.
  • can also return an HTTP status code. See Mozilla Status Codes.
• @JsonFormat: can configure how properties get serialized. The following example serializes the annotated field into a JSON STRING, with a pattern of dd-MM-yyyy hh:mm:ss.

    @JsonFormat(shape = JsonFormat.Shape.STRING, pattern = "dd-MM-yyyy hh:mm:ss")

• @Valid: validates fields based on your constraints

Exception Handling

• @ControllerAdvice: class-level annotation that allows you to define global exception handlers.
• handleMethodArgumentNotValid: method that can be overridden from the ResponseEntityExceptionHandler parent class. You can handle field violations and get the BindingResult here.
• @ExceptionHandler: method-level annotation that defines an exception handler.

1. Define the exception that you want the method to handle.
2. Pass the exception into the list of arguments.