Spring Boot up and Running

Chap 1: in nutshell

3 foundational features:

1. starters for dependency management
2. Executable JARs for Simplified Deployment
   • instead of shading (combining dependency + app JARs into one), nest JARs
   • can run the app
     • simple java -jar <SpringBootAppName.jar>
     • make the Jar self-executable
3. convention over configuration
   • autoconfig
   • defaults favor local dev environment

Chap 2: Choosing Tools and Getting Started

• Maven vs Gradle
  • Maven:
    • project structure strict convention
      • rigic declarative -> consistency -> less issues
  • Gradle:
    • Incremental compilation, only compile changes
    • allows scripting/programming
    • flexibility -> more tweaking and troubleshooting
• Java vs Kotlin
  • Kotlin
    • benefits:
      • less verbose
      • safe: by default no null values
      • define own syntax with "extension function" and "infix" - more readable

Chap 3: REST API

• use https://httpie.io/ to test REST APIs (over Curl, postman)

• Use class-level @RequestMapping (Private) annotation for shared URL portion

  @RestController
  @RequestMapping("/coffees")
  class RestApiDemoController {
  

• Use ResponseEntity to include status codes.

  @PutMapping("/{id}")
  ResponseEntity<Coffee> putCoffee(@PathVariable String id,
          @RequestBody Coffee coffee) {
      
      ...
      
      return (coffeeIndex == -1) ?
              new ResponseEntity<>(postCoffee(coffee), HttpStatus.CREATED) :
              new ResponseEntity<>(coffee, HttpStatus.OK);
  }
  

Chap 4: DB access

• @entity on model, no-arg constructor, setters on all fields
• Repository
  • CrudRepository with generic CRUD operations
  • JpaRepository extends CrudRepository

Chap 5: Config

• @ConfigurationProperties(prefix = "greeting")
• @ConfigurationPropertiesScan
• need spring-boot-configuration-processor dependency
• Autoconfiguration Report
  • java -jar bootapplication.jar --debug
  • java -Ddebug=true -jar bootapplication.jar
  • export DEBUG=true in shell
  • add debug=true to application.properties file
• Actuator
  • runtime info get/set
  • need spring-boot-starter-actuator dependency
  • secure by default with little info
  • opening it up
    • management.endpoints.web.exposure.include
    • management.endpoint.health.show-details=always or when_authorized
  • query
    • /actuator/env - get env variable and where config props comes from
    • /actuator/beans - all beans created
    • actuator/health - Health info (basic or expanded, depending on settings)
    • /actuator/loggers
      • echo '{"configuredLevel": "TRACE"}' | http :8080/actuator/loggers/org.springframework.data.web change logger level on the fly
    • /actuator/mappings
    • /actuator/heapdump and /actuator/threaddump
    • /actuator/metrics