Template CallBack - 2

1. Callback

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public interface TraceCallback<T> {

    T call();
}

 

 

 

2. TraceTemplate

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• TraceTemplate 는 템플릿 역할을 한다.
• execute(..) 를 보면 message 데이터와 콜백인 TraceCallback callback 을 전달 받는다.
• <T> 제네릭을 사용했다. 반환 타입을 정의한다.

public class TraceTemplate {

    private final LogTrace trace;

    public TraceTemplate(LogTrace trace) {
        this.trace = trace;
    }

    public <T> T execute(String message, TraceCallback<T> callback){
        TraceStatus status = null;

        try{
            status = trace.begin(message);

            //로직 호출, 변하는 부분
            T result = callback.call();

            trace.end(status);
            return result;

        }catch (Exception e){
            trace.exception(status, e);
            throw e;
        }
    }
}

 

 

3. Controller V5

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@RestController //@Controller +@ResponseBody
//@RequiredArgsConstructor
public class OrderControllerV5 {

    private final OrderServiceV5 orderService;
    private final TraceTemplate traceTemplate;

    public OrderControllerV5(OrderServiceV5 orderService, LogTrace trace) {
        this.orderService = orderService;
        this.traceTemplate = new TraceTemplate(trace);
    }

    @GetMapping("/v5/request")
    public String request(String itemId){

       return traceTemplate.execute("OrderController.request()", new TraceCallback<>() {
            @Override
            public String call() {
                orderService.orderItem(itemId);
                return "ok";
            }
        });

    }
}

• this.template = new TraceTemplate(trace)
  • trace 의존관계 주입을 받으면서 필요한 TraceTemplate 템플릿을 생성한다. 
  • 참고로 TraceTemplate 를 처음부터 스프링 빈으로 등록하고 주입받아도 된다. 이 부분은 선택이다.
• template.execute(.., new TraceCallback(){..})
  • 템플릿을 실행하면서 콜백을 전달한다.
  • 여기서는 콜백으로 익명 내부 클래스를 사용했다.

 

 

4. ServiceV5

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@Service
public class OrderServiceV5 {

    private final OrderRepositoryV5 orderRepository;
    private final TraceTemplate template;

    public OrderServiceV5(OrderRepositoryV5 orderRepository, LogTrace trace) {
        this.orderRepository = orderRepository;
        this.template = new TraceTemplate(trace);
    }

    public void orderItem(String itemId){

        template.execute("OrderService.orderItem()", () -> {
            orderRepository.save(itemId);
            return null;
        });
    }
}

 

• template.execute(.., new TraceCallback(){..}) : 템플릿을 실행하면서 콜백을 전달한다.
• 여기서는 콜백으로 람다를 전달했다.

 

5. RepositoryV5

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@Repository
public class OrderRepositoryV5 {

   private final TraceTemplate template;

    public OrderRepositoryV5(LogTrace trace) {
        this.template = new TraceTemplate(trace);
    }

    public void save(String itemId){

        template.execute("OrderRepository.save()", () ->{
            if (itemId.equals("ex")){
                throw new IllegalStateException("예외 발생");
            }
            sleep(1000);
            return "ok";
        });

    }

    private void sleep(int millis) {
        try {
            Thread.sleep(millis);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
}

 

 

6. GitHub : 211122 Template Callback2

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GitHub - bsh6463/Spring_Advanced: initial