Spring Boot Bootcamp – Workbooks and Challenges
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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.

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

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