Spring MVC — Bir İstek Controller'a Nasıl Ulaşır?

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@Component
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@Order(Ordered.HIGHEST_PRECEDENCE)
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class CorrelationIdFilter extends OncePerRequestFilter {
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    private static final String HEADER = "X-Correlation-Id";
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    @Override
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    protected void doFilterInternal(HttpServletRequest request, HttpServletResponse response, FilterChain chain)
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            throws ServletException, IOException {
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        String id = Optional.ofNullable(request.getHeader(HEADER)).orElseGet(() -> UUID.randomUUID().toString());
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        MDC.put("correlationId", id);
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        response.setHeader(HEADER, id);
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        try {
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            chain.doFilter(request, response);
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        } finally {
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            // The thread goes back to the pool; a leftover id would leak into the next request's logs.
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            MDC.remove("correlationId");
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        }
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    }
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}

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@Component
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class AuditInterceptor implements HandlerInterceptor {
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    private final AuditLog audit;
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    AuditInterceptor(AuditLog audit) {
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        this.audit = audit;
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    }
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    @Override
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    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) {
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        if (handler instanceof HandlerMethod method) {
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            request.setAttribute("audit.action", method.getMethod().getName());
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        }
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        return true;
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    }
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    // Runs after success and after failure alike, as long as preHandle returned true.
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    @Override
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    public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) {
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        audit.record(request.getUserPrincipal(), (String) request.getAttribute("audit.action"), response.getStatus());
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    }
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}

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@Configuration
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class WebConfig implements WebMvcConfigurer {
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    private final AuditInterceptor audit;
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    WebConfig(AuditInterceptor audit) {
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        this.audit = audit;
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    }
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    @Override
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    public void addInterceptors(InterceptorRegistry registry) {
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        registry.addInterceptor(audit).addPathPatterns("/transfers/**", "/accounts/**");
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    }
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}

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@RestController
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@RequestMapping("/transfers")
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class TransferController {
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    private final TransferService transfers;
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    TransferController(TransferService transfers) {
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        this.transfers = transfers;
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    }
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    @PostMapping
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    ResponseEntity<TransferResponse> create(@Valid @RequestBody TransferRequest request) {
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        TransferResponse done = transfers.send(request);
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        return ResponseEntity.status(HttpStatus.CREATED).body(done);
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    }
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}
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record TransferRequest(@NotBlank String fromIban, @NotBlank String toIban, @NotNull @Positive BigDecimal amount) {
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}

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@RestControllerAdvice
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class ApiErrors {
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    @ExceptionHandler(InsufficientFundsException.class)
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    ProblemDetail insufficient(InsufficientFundsException e) {
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        ProblemDetail body = ProblemDetail.forStatusAndDetail(HttpStatus.UNPROCESSABLE_ENTITY, "Bakiye yetersiz");
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        body.setProperty("accountId", e.accountId());
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        return body;
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    }
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    @ExceptionHandler(MethodArgumentNotValidException.class)
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    ProblemDetail invalid(MethodArgumentNotValidException e) {
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        ProblemDetail body = ProblemDetail.forStatusAndDetail(HttpStatus.BAD_REQUEST, "İstek alanları geçersiz");
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        body.setProperty("fields", e.getBindingResult().getFieldErrors().stream()
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                .collect(Collectors.toMap(FieldError::getField, f -> String.valueOf(f.getDefaultMessage()), (a, b) -> a)));
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        return body;
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    }
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}