confident-spring-03-webmvc-restservices

This repository is related to module 3 in Marco Behler's course "The confident Spring professional" https://www.marcobehler.com/ which I purchased in order to understand the fundamentals of Spring. The course starts with plain Java backend and introduces plain Spring features little by little, showcasing what Spring Boot hides under the hood. At the end of the course Spring Boot features are implemented.

Learning goals

• Spring WebMVC setup.
• Writing REST services with WebMVC.
• Controllers.
• Extracting path variables and parameters with annotations.
• Mapping json request to DTO.
• Validation (JSR 303/Hibernate).
• Content negotiation: responses in both JSON and XML.
• Exception handling against bad request.

Key takeaways

• DispatcherServlet's jobis to dispatch requests and responses to and from controllers

• DispatcherServlet is constructed from WebApplicationContect which is constructed from configuration.class

• @Controller tells Spring that your class contains methods that can return something HTTP related (HTML, JSON, XML) to the browser.

• @ResponseBody tells Spring, that you want to write JSON/XML/plain text directly to the HttpServletOutputstream

• @RestController = @Controller + @ResponseBody

• @GetMapping("/invoices") is a shorthand annotation for RequestMapping(value = "/invoices", method = RequestMethod.GET)

• @EnableWebMvc Spring Web MVC get initialized with default configuration, e.g. registers jackson dependency i.e. enables JSON <-> Java object conversion.

• @RequestParam @PathVariable @RequestBody (DTO, @JsonProperty) for extracting incoming data.

• Hibernate-validator(&expressly) is one popular validation framework: With that you can check that incoming JSON is valid against dto (@Valid + validation-annotations in DTO).

• @Validated (in Controller) + MethodValidationProcessor (in config) enables parameter and pathvariable validation.

• @RestControllerAdvice applies to both @Controller and @RestController and writes JSON/XML to response body

• @ControllerAdvice applies also to both @Controller and @RestController but writes HTML.

• With the help of Jackson libraries, Java objects can be written to response body in JSON/XML, based on content negotiation.

  Getting Started

To run the application, you have two choices:

1. Run locally
2. Run in Docker

Locally

1. Ensure all the dependencies are installed
2. Clone the repository
3. Build the project using Maven:

   mvn clean install

4. Run the application with:

   java -jar target/pdfinvoices-1.0-SNAPSHOT.jar

Run in Docker

1. Build the image:

   docker build . -t confident-03:latest     

2. Run the image:

   docker run -it -p 8080:8080 confident-03:latest 

3. Open the api in http://localhost:8080

Documentation

Endpoints for local use:

• GET "/"
• GET "/invoices"
• POST "/invoices?user_id=jeff&amount=40"
• POST "/invoices/jeff/40"
• POST "/invoicesbody" + user_id & amount in request body
• Content negotiation: Request header's Accept and Content-Type can both be either "application/json" or "application/xml"