Spring in Action

Chpt 2: Wiring beans

Auto configuration

• @Autowired works on both constructor and method (will create dependent beans, and throw error if can't find)
• @Autowired is spring specific, use @Inject from java, mostly interchangable
• when using @ComponentScan, better to use basePackageClasses to be refactor proof

Manual wiring:

• @bean by default ID = method name. override it with name=

• by default, all beans in spring are singletons.

  @Bean
  public CompactDisc sgtPeppers(){
    return new SgtPappers();
  }
  

  if directly call the method that a bean annotation is on, e.g. sgtPepeprs() will return the singleton rather than creating another instance.

  Chpt 3: Advanced wiring

• @Profile("dev") annotation for beans only created when active profiles include dev

• @Conditional(MagicExistsCondition.class) for custom conditions

  • Condition interface comes with 2 params: matches(ConditionContext context, AnnotatedTypeMetadata metadata)
  • ConditionContext
    • bean registry: bean definitions
    • bean factory: presence of beans
    • environment: env varialbes
    • resource loader: resources loaded
    • class loader: class loaded

• disambiguating beans

  • @Primary

  • @Qualifier("cold)

  • Use custom qualifier annotations to allow multiple qualifiers - @Cold

    @Target({ElementType.FIELD, ElementType.PARAMETER, ElementType.TYPE})
    @Retention(RetentionPolicy.RUNTIME)
    @Qualifier
    public @interface Cold {
    }
    

• @Scope

  • singleton
  • prototype - created each time is injected
  • session - in web app, one for each session. e.g. shopping cart
  • request
    • scope proxy

Chpt4: Aspect oriented Spring

• basic concepts:

• unlike AspectJ, spring is proxy based, and only supports method interception

  

• wrap method options:

  • @After
  • @AfterReturning
  • @AfterThrowing
  • @Around
  • @Before

• also possible to add methods using Introduction