Spring Boot

Setup

• Start new project with Initializr
  • Make sure you add the Spring Web dependency for REST apps

Layout

• App files are in src/main/java/com/example/project/
• By default, Maven compiles sources from src/main/java

Controllers

Annotated controllers have flexible method signatures and do not have to extend base classes nor implement specific interfaces.

• Annotate with @RestController - Tells Spring to render the resulting string back to the caller
  • Equivalent to @Controller + @ResponseBody
• @ResponseBody means the controller writes directly to the HTTP response instead of going through an HTML template first
• @RequestMapping("/path") - Routing information for requests, matches all methods. Can be used at the class level for routing.
  • @GetMapping
    • @GetMapping("/{id}") - Dynamic segment, access with @PathVariable Long id in signature
  • @PostMapping
  • @PutMapping
  • @PatchMapping
  • @DeleteMapping
• Can match on other values: @PostMapping(path = "/pets", consumes = "application/json", produces = "application/json", headers = "myHeader=myValue", params = "myParam=myValue")
• @ResponseStatus(HttpStatus.CREATED) for setting response
• Can match paths with exact match, glob, or dynamic segment
• Multiple patterns are matched by specificity scoring
• Method arguments include (docs):
  • WebRequest - The entire HTTP response
  • @RequestParam("paramName")
  • @PathVariable
  • @RequestBody
  • @RequestPart (Form)
• Method return values include (docs):
  • @ResponseBody
  • String - Name of a view to use
  • void - Use if the response status is handled by the @ResponseStatus annotation
• @JsonView("serializerName") to return a model and serialize the response
• @CrossOrigin puts CORS headers on responses (allowed at both method and class level)

package com.example.demo;

import java.util.concurrent.atomic.AtomicLong;

import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class GreetingController {

  private static final String template = "Hello, %s!";
  private final AtomicLong counter = new AtomicLong();

  @GetMapping("/greeting")
  public Greeting greeting(@RequestParam(value = "name", defaultValue = "World") String name) {
    return new Greeting(counter.incrementAndGet(), String.format(template, name));
  }
}

Running The Server

With Maven: ./mvnw spring-boot:run (runs on 8080)

Building

• ./mvnw package builds the app into a .jar file in the /target folder

Questions

• How does model work?