MS Lesson 17: Exception Handling


1. Ilk once eger bizim proyektde Global Exception Handler olmadigi ucun program exception atsa Spring onu 500 Internal Server Error kimi qaytarir.

Bu tipli response aliriq:

{

  "timestamp": "2026-05-14T17:17:04.482Z",

  "status": 500,

  "error": "Internal Server Error",

  "path": "/find-by-id/1"

}


2. Hetta bu terzde yazsaq bele bu problemi hell etmir:

@Transactional
public Account foo(Long id) {
    return accountRepository.findById(id).orElseThrow(() -> new RuntimeException("Xeta"));
}


3. Bu problemi hell etmek ucun, sade model quraq. 

package guru.springframework.cruddemo.error;

import java.time.Instant;

import com.fasterxml.jackson.annotation.JsonInclude;

import lombok.AllArgsConstructor;
import lombok.Builder;
import lombok.Data;
import lombok.NoArgsConstructor;

@Data
@Builder
@NoArgsConstructor
@AllArgsConstructor
@JsonInclude(JsonInclude.Include.NON_NULL)
public class ErrorResponse {

    private Integer status;
    private String code;
    private String message;
    private Instant timestamp;
    private String path;

}

response model:

{

  "status": 404,

  "code": "ACCOUNT_NOT_FOUND",

  "message": "Account was not found",

  "timestamp": "2026-05-14T10:15:30Z"

}



Novbeti addim ise BaseException model qura bilerik.

package guru.springframework.cruddemo.error;

import java.util.Arrays;

import org.springframework.http.HttpStatus;

import lombok.Getter;

@Getter
public class BaseException extends RuntimeException {

    private final ErrorCode errorCode;
    private final Object[] detailsParams;

    public BaseException(ErrorCode errorCode) {
        super(errorCode.getMessage());
        this.errorCode = errorCode;
        this.detailsParams = new Object[0];
    }

    public BaseException(ErrorCode errorCode, Object... detailsParams) {
        super(errorCode.getMessage());
        this.errorCode = errorCode;
        this.detailsParams = copyParams(detailsParams);
    }

    public BaseException(ErrorCode errorCode, Throwable cause) {
        super(errorCode.getMessage(), cause);
        this.errorCode = errorCode;
        this.detailsParams = new Object[0];
    }

    public BaseException(ErrorCode errorCode, Throwable cause, Object... detailsParams) {
        super(errorCode.getMessage(), cause);
        this.errorCode = errorCode;
        this.detailsParams = copyParams(detailsParams);
    }

    private static Object[] copyParams(Object... detailsParams) {
        if (detailsParams == null || detailsParams.length == 0) {
            return new Object[0];
        }
        return Arrays.copyOf(detailsParams, detailsParams.length);
    }

    public String getFormattedDetails() {
        return errorCode.formatDetails(detailsParams);
    }

    public HttpStatus getHttpStatus() {
        return errorCode.getHttpStatus();
    }
}



package guru.springframework.cruddemo.error;

import java.text.MessageFormat;
import java.util.Arrays;

import org.springframework.http.HttpStatus;

import com.fasterxml.jackson.annotation.JsonCreator;
import com.fasterxml.jackson.annotation.JsonValue;

import lombok.Getter;
import lombok.RequiredArgsConstructor;

@Getter
@RequiredArgsConstructor
public enum ErrorCode {

    VALIDATION_FAILED(
            "VALIDATION_FAILED",
            "Validation failed",
            "One or more fields failed validation.",
            HttpStatus.BAD_REQUEST),
    METHOD_VALIDATION_FAILED(
            "METHOD_VALIDATION_FAILED",
            "Method validation failed",
            "One or more method parameters failed validation.",
            HttpStatus.BAD_REQUEST),
    CONSTRAINT_VIOLATION(
            "CONSTRAINT_VIOLATION",
            "Constraint violation",
            "One or more constraints were violated.",
            HttpStatus.BAD_REQUEST),
    REQUEST_BODY_NOT_READABLE(
            "REQUEST_BODY_NOT_READABLE",
            "Malformed request body",
            "Request body is missing or malformed.",
            HttpStatus.BAD_REQUEST),
    MISSING_REQUEST_PARAMETER(
            "MISSING_REQUEST_PARAMETER",
            "Missing request parameter",
            "A required request parameter is missing.",
            HttpStatus.BAD_REQUEST),
    TYPE_MISMATCH(
            "TYPE_MISMATCH",
            "Type mismatch",
            "Request parameter type is invalid.",
            HttpStatus.BAD_REQUEST),
    BAD_REQUEST(
            "BAD_REQUEST",
            "Bad request",
            "Request is malformed or contains invalid data.",
            HttpStatus.BAD_REQUEST),
    AKB_INTEGRATION_ERROR(
            "AKB_INTEGRATION_ERROR",
            "AKB integration error",
            "AKB integration failed during {0}.",
            HttpStatus.SERVICE_UNAVAILABLE),
    INTERNAL_SERVER_ERROR(
            "INTERNAL_SERVER_ERROR",
            "Internal server error",
            "An unexpected error occurred.",
            HttpStatus.INTERNAL_SERVER_ERROR),
    SUBMISSION_ALREADY_EXISTS(
            "IDEMPOTENCY_KEY_EXISTS",
            "Submission with this idempotency key already exists",
            "A credit submission with idempotency key ''{0}'' has already been processed. This is a duplicate request. If you need to submit a new credit, please generate a new idempotency key.",
            HttpStatus.CONFLICT),
    SUBMISSION_NOT_FOUND(
            "SUBMISSION_NOT_FOUND",
            "Submission not found",
            "Submission with ID ''{0}'' was not found.",
            HttpStatus.NOT_FOUND),
    SCORING_INQUIRY_NOT_FOUND(
            "SCORING_INQUIRY_NOT_FOUND",
            "Scoring inquiry not found",
            "Scoring inquiry with ID ''{0}'' was not found.",
            HttpStatus.NOT_FOUND),
    ACCOUNT_NOT_FOUND(
            "ACCOUNT_NOT_FOUND",
            "Account not found",
            "Account with ID ''{0}'' was not found.",
            HttpStatus.NOT_FOUND),

    UNKNOWN(
            "UNKNOWN",
            "Unknown error",
            "An unrecognized error code was received.",
            HttpStatus.INTERNAL_SERVER_ERROR);

    @Getter(onMethod_ = @JsonValue)
    private final String code;
    private final String message;
    private final String detailsTemplate;
    private final HttpStatus httpStatus;

    public String formatDetails(Object... params) {
        if (params == null || params.length == 0) {
            return this.detailsTemplate;
        }
        return MessageFormat.format(this.detailsTemplate, params);
    }

    @JsonCreator
    public static ErrorCode fromCode(String value) {
        if (value == null || value.isBlank()) {
            return null;
        }
        return Arrays.stream(values())
                .filter(c -> c.code.equals(value))
                .findFirst()
                .orElse(UNKNOWN);
    }
}


Indi ise exceptionu spesifikleshdire bilerik:

package guru.springframework.cruddemo.error;

public class AccountNotFoundException extends BaseException {

    public AccountNotFoundException(Long accountId) {
        super(ErrorCode.ACCOUNT_NOT_FOUND, accountId);
    }
    
}


Novbeti addim ise GlobalExceptionHandler yazmaq lazimdir:

package guru.springframework.cruddemo.error;

import java.time.Instant;

import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.ExceptionHandler;
import org.springframework.web.bind.annotation.RestControllerAdvice;

import lombok.extern.slf4j.Slf4j;
import org.springframework.web.context.request.ServletWebRequest;
import org.springframework.web.context.request.WebRequest;

@Slf4j
@RestControllerAdvice
public class GlobalExceptionHandler {

    @ExceptionHandler(BaseException.class)
    public ResponseEntity<ErrorResponse> handleBaseException(BaseException ex, WebRequest request) {
        ErrorResponse body = ErrorResponse.builder()
                .status(ex.getHttpStatus().value())
                .code(ex.getErrorCode().getCode())
                .message(ex.getFormattedDetails())
                .timestamp(Instant.now())
                .path(((ServletWebRequest) request).getRequest().getRequestURI())
                .build();
        return ResponseEntity.status(ex.getHttpStatus()).body(body);
    }

    @ExceptionHandler(Exception.class)
    public ResponseEntity<ErrorResponse> handleUnexpected(Exception ex, WebRequest request) {
        log.error("Unhandled exception", ex);
        ErrorCode code = ErrorCode.INTERNAL_SERVER_ERROR;
        ErrorResponse body = ErrorResponse.builder()
                .status(code.getHttpStatus().value())
                .code(code.getCode())
                .message(code.getMessage())
                .timestamp(Instant.now())
                .path(((ServletWebRequest) request).getRequest().getRequestURI())
                .build();
        return ResponseEntity.status(code.getHttpStatus()).body(body);
    }

}




Indi ise field-ler ucun error model quraq. 

package guru.springframework.cruddemo.controller;

import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

import guru.springframework.cruddemo.dto.CreateAccountRequest;
import jakarta.validation.Valid;
import lombok.extern.slf4j.Slf4j;

@Slf4j
@RestController
@RequestMapping("/validation-demo")
public class ValidationDemoController {

    @PostMapping("/accounts")
    public ResponseEntity<String> createAccount(@Valid @RequestBody CreateAccountRequest request) {
        log.info("Valid request: name={}, email={}, balance={}",
                request.getName(), request.getEmail(), request.getBalance());
        return ResponseEntity.ok("Validation passed");
    }

}


package guru.springframework.cruddemo.dto;

import java.math.BigDecimal;

import jakarta.validation.constraints.Email;
import jakarta.validation.constraints.NotBlank;
import jakarta.validation.constraints.NotNull;
import jakarta.validation.constraints.Positive;
import lombok.Data;

@Data
public class CreateAccountRequest {

    @NotBlank(message = "name must not be blank")
    private String name;

    @NotBlank(message = "email must not be blank")
    @Email(message = "email must be valid")
    private String email;

    @NotNull(message = "balance must not be null")
    @Positive(message = "balance must be greater than zero")
    private BigDecimal balance;

}


Field error tutulmasa response bu shekilde gelecek:

{

  "status": 500,

  "code": "INTERNAL_SERVER_ERROR",

  "message": "Internal server error",

  "timestamp": "2026-05-16T07:23:22.083954Z",

  "path": "/validation-demo"

}



Bunun ucun ayrica error response model qururuq:

package guru.springframework.cruddemo.error;

import com.fasterxml.jackson.annotation.JsonInclude;

import lombok.AllArgsConstructor;
import lombok.Builder;
import lombok.Data;
import lombok.NoArgsConstructor;

@Data
@Builder
@NoArgsConstructor
@AllArgsConstructor
@JsonInclude(JsonInclude.Include.NON_NULL)
public class FieldErrorDto {

    private String field;
    private String message;

}


package guru.springframework.cruddemo.error;

import java.time.Instant;
import java.util.List;

import com.fasterxml.jackson.annotation.JsonInclude;

import lombok.AllArgsConstructor;
import lombok.Builder;
import lombok.Data;
import lombok.NoArgsConstructor;

@Data
@Builder
@NoArgsConstructor
@AllArgsConstructor
@JsonInclude(JsonInclude.Include.NON_NULL)
public class ErrorResponse {

    private Integer status;
    private String code;
    private String message;
    private Instant timestamp;
    private String path;
    private List<FieldErrorDto> fieldErrors;

}


package guru.springframework.cruddemo.error;

import java.time.Instant;
import java.util.List;

import org.springframework.http.ResponseEntity;
import org.springframework.http.converter.HttpMessageNotReadableException;
import org.springframework.web.bind.MethodArgumentNotValidException;
import org.springframework.web.bind.annotation.ExceptionHandler;
import org.springframework.web.bind.annotation.RestControllerAdvice;
import org.springframework.web.context.request.ServletWebRequest;
import org.springframework.web.context.request.WebRequest;

import lombok.extern.slf4j.Slf4j;

@Slf4j
@RestControllerAdvice
public class GlobalExceptionHandler {

    @ExceptionHandler(BaseException.class)
    public ResponseEntity<ErrorResponse> handleBaseException(BaseException ex, WebRequest request) {
        ErrorResponse body = ErrorResponse.builder()
                .status(ex.getHttpStatus().value())
                .code(ex.getErrorCode().getCode())
                .message(ex.getFormattedDetails())
                .timestamp(Instant.now())
                .path(requestPath(request))
                .build();
        return ResponseEntity.status(ex.getHttpStatus()).body(body);
    }

    @ExceptionHandler(MethodArgumentNotValidException.class)
    public ResponseEntity<ErrorResponse> handleMethodArgumentNotValid(
            MethodArgumentNotValidException ex,
            WebRequest request) {
        ErrorCode code = ErrorCode.VALIDATION_FAILED;
        List<FieldErrorDto> fieldErrors = ex.getBindingResult().getFieldErrors().stream()
                .map(fieldError -> FieldErrorDto.builder()
                        .field(fieldError.getField())
                        .message(fieldError.getDefaultMessage())
                        .build())
                .toList();
        ErrorResponse body = ErrorResponse.builder()
                .status(code.getHttpStatus().value())
                .code(code.getCode())
                .message(code.getMessage())
                .timestamp(Instant.now())
                .path(requestPath(request))
                .fieldErrors(fieldErrors)
                .build();
        return ResponseEntity.status(code.getHttpStatus()).body(body);
    }

    @ExceptionHandler(HttpMessageNotReadableException.class)
    public ResponseEntity<ErrorResponse> handleHttpMessageNotReadable(
            HttpMessageNotReadableException ex,
            WebRequest request) {
        ErrorCode code = ErrorCode.REQUEST_BODY_NOT_READABLE;
        ErrorResponse body = ErrorResponse.builder()
                .status(code.getHttpStatus().value())
                .code(code.getCode())
                .message(code.getMessage())
                .timestamp(Instant.now())
                .path(requestPath(request))
                .build();
        return ResponseEntity.status(code.getHttpStatus()).body(body);
    }

    @ExceptionHandler(Exception.class)
    public ResponseEntity<ErrorResponse> handleUnexpected(Exception ex, WebRequest request) {
        log.error("Unhandled exception", ex);
        ErrorCode code = ErrorCode.INTERNAL_SERVER_ERROR;
        ErrorResponse body = ErrorResponse.builder()
                .status(code.getHttpStatus().value())
                .code(code.getCode())
                .message(code.getMessage())
                .timestamp(Instant.now())
                .path(requestPath(request))
                .build();
        return ResponseEntity.status(code.getHttpStatus()).body(body);
    }

    private static String requestPath(WebRequest request) {
        if (request instanceof ServletWebRequest servletWebRequest) {
            return servletWebRequest.getRequest().getRequestURI();
        }
        return request.getDescription(false);
    }

}











==========================================================================




package com.azercell.akbintegrationservice.error.enums;

import lombok.Getter;
import lombok.RequiredArgsConstructor;
import org.springframework.http.HttpStatus;

import java.text.MessageFormat;

@Getter
@RequiredArgsConstructor
public enum ErrorCode {

    VALIDATION_FAILED(
            "VALIDATION_FAILED",
            "Validation failed",
            "One or more fields failed validation.",
            HttpStatus.BAD_REQUEST
    ),
    METHOD_VALIDATION_FAILED(
            "METHOD_VALIDATION_FAILED",
            "Method validation failed",
            "One or more method parameters failed validation.",
            HttpStatus.BAD_REQUEST
    ),
    CONSTRAINT_VIOLATION(
            "CONSTRAINT_VIOLATION",
            "Constraint violation",
            "One or more constraints were violated.",
            HttpStatus.BAD_REQUEST
    ),
    REQUEST_BODY_NOT_READABLE(
            "REQUEST_BODY_NOT_READABLE",
            "Malformed request body",
            "Request body is missing or malformed.",
            HttpStatus.BAD_REQUEST
    ),
    MISSING_REQUEST_PARAMETER(
            "MISSING_REQUEST_PARAMETER",
            "Missing request parameter",
            "A required request parameter is missing.",
            HttpStatus.BAD_REQUEST
    ),
    TYPE_MISMATCH(
            "TYPE_MISMATCH",
            "Type mismatch",
            "Request parameter type is invalid.",
            HttpStatus.BAD_REQUEST
    ),
    BAD_REQUEST(
            "BAD_REQUEST",
            "Bad request",
            "Request is malformed or contains invalid data.",
            HttpStatus.BAD_REQUEST
    ),
    AKB_INTEGRATION_ERROR(
            "AKB_INTEGRATION_ERROR",
            "AKB integration error",
            "AKB integration failed during {0}.",
            HttpStatus.SERVICE_UNAVAILABLE
    ),
    INTERNAL_SERVER_ERROR(
            "INTERNAL_SERVER_ERROR",
            "Internal server error",
            "An unexpected error occurred.",
            HttpStatus.INTERNAL_SERVER_ERROR
    ),
    SUBMISSION_ALREADY_EXISTS(
            "IDEMPOTENCY_KEY_EXISTS",
            "Submission with this idempotency key already exists",
            "A credit submission with idempotency key ''{0}'' has already been processed. This is a duplicate request. If you need to submit a new credit, please generate a new idempotency key.",
            HttpStatus.CONFLICT
    ),
    SUBMISSION_NOT_FOUND(
            "SUBMISSION_NOT_FOUND",
            "Submission not found",
            "Submission with ID ''{0}'' was not found.",
            HttpStatus.NOT_FOUND
    ),
    SCORING_INQUIRY_NOT_FOUND(
            "SCORING_INQUIRY_NOT_FOUND",
            "Scoring inquiry not found",
            "Scoring inquiry with ID ''{0}'' was not found.",
            HttpStatus.NOT_FOUND
    ),
    ;

    private final String code;
    private final String message;
    private final String detailsTemplate;
    private final HttpStatus httpStatus;

    public String formatDetails(Object... params) {
        if (params == null || params.length == 0) {
            return this.detailsTemplate;
        }
        return MessageFormat.format(this.detailsTemplate, params);
    }

} 


package com.azercell.akbintegrationservice.error.model;

import com.fasterxml.jackson.annotation.JsonInclude;
import lombok.AllArgsConstructor;
import lombok.Builder;
import lombok.Data;
import lombok.NoArgsConstructor;

import java.time.Instant;
import java.util.List;
import java.util.Map;

@Data
@Builder
@NoArgsConstructor
@AllArgsConstructor
@JsonInclude(JsonInclude.Include.NON_NULL)
public class ErrorResponse {

    private String traceId;
    private Integer status;
    private String reason;
    private String code;
    private String message;
    private String details;
    private String path;
    private Instant timestamp;
    private List<ValidationError> validationErrors;
    private Map<String, Object> additionalProperties;

    @Data
    @Builder
    @NoArgsConstructor
    @AllArgsConstructor
    @JsonInclude(JsonInclude.Include.NON_NULL)
    public static class ValidationError {

        private String field;
        private Object value;
        private String message;
        private String code;

    }

}



package com.azercell.akbintegrationservice.error.model;

import com.azercell.akbintegrationservice.error.enums.ErrorCode;
import com.fasterxml.jackson.annotation.JsonInclude;
import lombok.AllArgsConstructor;
import lombok.Builder;
import lombok.Data;
import lombok.NoArgsConstructor;

@Data
@Builder
@NoArgsConstructor
@AllArgsConstructor
@JsonInclude(JsonInclude.Include.NON_NULL)
public class ExternalServiceErrorResponse {

    private String timestamp;
    private Integer status;
    private String error;
    private String message;
    private String path;
    private ErrorCode errorCode;

}



package com.azercell.akbintegrationservice.error.handler;

import com.azercell.akbintegrationservice.error.enums.ErrorCode;
import com.azercell.akbintegrationservice.error.exceptions.AkbIntegrationException;
import com.azercell.akbintegrationservice.error.exceptions.ExternalServiceException;
import com.azercell.akbintegrationservice.error.exceptions.IdempotencyConflictException;
import com.azercell.akbintegrationservice.error.exceptions.ScoringInquiryNotFoundException;
import com.azercell.akbintegrationservice.error.exceptions.SubmissionNotFoundException;
import com.azercell.akbintegrationservice.error.model.ErrorResponse;
import com.azercell.akbintegrationservice.error.model.ExternalServiceErrorResponse;
import com.azercell.akbintegrationservice.logging.filter.RequestIdFilter;
import jakarta.servlet.http.HttpServletRequest;
import jakarta.validation.ConstraintViolation;
import jakarta.validation.ConstraintViolationException;
import lombok.extern.slf4j.Slf4j;
import org.jspecify.annotations.Nullable;
import org.slf4j.MDC;
import org.springframework.beans.TypeMismatchException;
import org.springframework.context.MessageSourceResolvable;
import org.springframework.http.HttpHeaders;
import org.springframework.http.HttpStatus;
import org.springframework.http.HttpStatusCode;
import org.springframework.http.ResponseEntity;
import org.springframework.http.converter.HttpMessageNotReadableException;
import org.springframework.validation.FieldError;
import org.springframework.validation.ObjectError;
import org.springframework.validation.method.MethodValidationException;
import org.springframework.web.bind.MethodArgumentNotValidException;
import org.springframework.web.bind.MissingServletRequestParameterException;
import org.springframework.web.bind.annotation.ExceptionHandler;
import org.springframework.web.bind.annotation.RestControllerAdvice;
import org.springframework.web.context.request.ServletWebRequest;
import org.springframework.web.context.request.WebRequest;
import org.springframework.web.servlet.mvc.method.annotation.ResponseEntityExceptionHandler;

import java.time.Instant;
import java.util.List;
import java.util.Map;
import java.util.stream.Collectors;

@Slf4j
@RestControllerAdvice
public class GlobalExceptionHandler extends ResponseEntityExceptionHandler {

    @Override
    protected @Nullable ResponseEntity<Object> handleMethodArgumentNotValid(MethodArgumentNotValidException ex,
                                                                            HttpHeaders headers,
                                                                            HttpStatusCode status,
                                                                            WebRequest request) {
        String traceId = resolveTraceId();

        List<ErrorResponse.ValidationError> validationErrors = ex.getBindingResult()
                .getFieldErrors()
                .stream()
                .map(this::mapFieldError)
                .collect(Collectors.toList());

        ErrorCode errorCode = ErrorCode.VALIDATION_FAILED;
        String path = resolvePath(request);

        log.warn("Validation failed - traceId: {}, errors: {}, path: {}", traceId, validationErrors.size(), path);

        return ResponseEntity
                .status(errorCode.getHttpStatus())
                .body(buildErrorResponse(errorCode, traceId, path, validationErrors));
    }

    @Override
    protected @Nullable ResponseEntity<Object> handleHttpMessageNotReadable(HttpMessageNotReadableException ex,
                                                                            HttpHeaders headers,
                                                                            HttpStatusCode status,
                                                                            WebRequest request) {
        ErrorCode errorCode = ErrorCode.REQUEST_BODY_NOT_READABLE;
        String traceId = resolveTraceId();
        String path = resolvePath(request);

        log.warn("Malformed request body - traceId: {}, path: {}", traceId, path);

        return ResponseEntity
                .status(errorCode.getHttpStatus())
                .body(buildErrorResponse(errorCode, traceId, path));
    }

    @Override
    protected @Nullable ResponseEntity<Object> handleMissingServletRequestParameter(
            MissingServletRequestParameterException ex,
            HttpHeaders headers,
            HttpStatusCode status,
            WebRequest request
    ) {
        ErrorCode errorCode = ErrorCode.MISSING_REQUEST_PARAMETER;
        String traceId = resolveTraceId();
        String path = resolvePath(request);

        ErrorResponse.ValidationError validationError = ErrorResponse.ValidationError.builder()
                .field(ex.getParameterName())
                .message(ex.getMessage())
                .code("MissingServletRequestParameter")
                .build();

        log.warn("Missing request parameter - traceId: {}, path: {}", traceId, path);

        return ResponseEntity
                .status(errorCode.getHttpStatus())
                .body(buildErrorResponse(errorCode, traceId, path, List.of(validationError)));
    }

    @Override
    protected @Nullable ResponseEntity<Object> handleMethodValidationException(MethodValidationException ex, HttpHeaders headers, HttpStatus status, WebRequest request) {
        ErrorCode errorCode = ErrorCode.METHOD_VALIDATION_FAILED;
        String traceId = resolveTraceId();
        String path = resolvePath(request);

        List<ErrorResponse.ValidationError> validationErrors = ex.getAllErrors()
                .stream()
                .map(this::mapResolvableError)
                .collect(Collectors.toList());

        log.warn("Method validation failed - traceId: {}, errors: {}, path: {}", traceId, validationErrors.size(), path);

        return ResponseEntity
                .status(errorCode.getHttpStatus())
                .body(buildErrorResponse(errorCode, traceId, path, validationErrors));
    }

    @ExceptionHandler(ConstraintViolationException.class)
    public ResponseEntity<Object> handleConstraintViolationException(
            ConstraintViolationException ex,
            HttpServletRequest request
    ) {
        ErrorCode errorCode = ErrorCode.CONSTRAINT_VIOLATION;
        String traceId = resolveTraceId();
        String path = request.getRequestURI();

        List<ErrorResponse.ValidationError> validationErrors = ex.getConstraintViolations()
                .stream()
                .map(this::mapConstraintViolation)
                .collect(Collectors.toList());

        log.warn("Constraint violations - traceId: {}, errors: {}, path: {}", traceId, validationErrors.size(), path);

        return ResponseEntity
                .status(errorCode.getHttpStatus())
                .body(buildErrorResponse(errorCode, traceId, path, validationErrors));
    }

    @Override
    protected @Nullable ResponseEntity<Object> handleTypeMismatch(TypeMismatchException ex, HttpHeaders headers, HttpStatusCode status, WebRequest request) {
        ErrorCode errorCode = ErrorCode.TYPE_MISMATCH;
        String traceId = resolveTraceId();
        String path = resolvePath(request);

        ErrorResponse.ValidationError validationError = ErrorResponse.ValidationError.builder()
                .field(ex.getPropertyName())
                .value(ex.getValue())
                .message(ex.getMessage())
                .code("TypeMismatch")
                .build();

        log.warn("Type mismatch - traceId: {}, path: {}", traceId, path);

        return ResponseEntity
                .status(errorCode.getHttpStatus())
                .body(buildErrorResponse(errorCode, traceId, path, List.of(validationError)));
    }

    @Override
    protected @Nullable ResponseEntity<Object> handleExceptionInternal(Exception ex, @Nullable Object body, HttpHeaders headers, HttpStatusCode statusCode, WebRequest request) {
        ErrorCode errorCode = ErrorCode.INTERNAL_SERVER_ERROR;
        String traceId = resolveTraceId();
        String path = resolvePath(request);

        log.error("Unhandled exception - traceId: {}, path: {}", traceId, path, ex);

        return ResponseEntity
                .status(statusCode)
                .body(buildErrorResponse(errorCode, traceId, path));
    }

    @ExceptionHandler(ExternalServiceException.class)
    public ResponseEntity<Object> handleExternalServiceException(ExternalServiceException ex,
                                                                 WebRequest request) {
        ExternalServiceErrorResponse externalError = ex.getExternalServiceError();
        ErrorCode errorCode = ex.getErrorCode();

        String traceId = resolveTraceId();
        String path = externalError != null && externalError.getPath() != null
                ? externalError.getPath()
                : resolvePath(request);

        String detailsOverride = externalError != null && externalError.getMessage() != null
                ? externalError.getMessage()
                : errorCode.formatDetails();
        int status = externalError != null && externalError.getStatus() != null
                ? externalError.getStatus()
                : errorCode.getHttpStatus().value();
        String reason = externalError != null && externalError.getError() != null
                ? externalError.getError()
                : errorCode.getHttpStatus().getReasonPhrase();
        Map<String, Object> additionalProperties = externalError != null
                ? Map.of("externalServiceError", externalError)
                : Map.of();

        log.warn("External service error - traceId: {}, path: {}", traceId, path, ex);

        return ResponseEntity
                .status(status)
                .body(buildErrorResponseWithStatus(
                        errorCode,
                        traceId,
                        path,
                        detailsOverride,
                        List.of(),
                        additionalProperties,
                        status,
                        reason
                ));
    }

    @ExceptionHandler(AkbIntegrationException.class)
    public ResponseEntity<Object> handleAkbIntegrationException(AkbIntegrationException ex,
                                                                WebRequest request) {
        ErrorCode errorCode = ErrorCode.AKB_INTEGRATION_ERROR;
        String traceId = resolveTraceId();
        String path = resolvePath(request);

        log.warn("AKB integration error - traceId: {}, path: {}", traceId, path, ex);

        return ResponseEntity
                .status(errorCode.getHttpStatus())
                .body(buildErrorResponse(
                        errorCode,
                        traceId,
                        path,
                        ex.getFormattedDetails(),
                        null,
                        ex.getAdditionalProperties()
                ));
    }

    @ExceptionHandler(IdempotencyConflictException.class)
    public ResponseEntity<Object> handleIdempotencyConflict(IdempotencyConflictException ex,
                                                            WebRequest request) {
        ErrorCode errorCode = ErrorCode.SUBMISSION_ALREADY_EXISTS;
        String traceId = resolveTraceId();
        String path = resolvePath(request);

        log.warn("Idempotency conflict - traceId: {}, path: {}", traceId, path, ex);

        return ResponseEntity
                .status(errorCode.getHttpStatus())
                .body(buildErrorResponse(
                        errorCode,
                        traceId,
                        path,
                        ex.getFormattedDetails(),
                        null,
                        ex.getAdditionalProperties()
                ));
    }

    @ExceptionHandler(SubmissionNotFoundException.class)
    public ResponseEntity<Object> handleSubmissionNotFound(SubmissionNotFoundException ex,
                                                           WebRequest request) {
        ErrorCode errorCode = ErrorCode.SUBMISSION_NOT_FOUND;
        String traceId = resolveTraceId();
        String path = resolvePath(request);

        log.warn("Submission not found - traceId: {}, path: {}", traceId, path, ex);

        return ResponseEntity
                .status(errorCode.getHttpStatus())
                .body(buildErrorResponse(
                        errorCode,
                        traceId,
                        path,
                        ex.getFormattedDetails(),
                        null,
                        ex.getAdditionalProperties()
                ));
    }

    @ExceptionHandler(ScoringInquiryNotFoundException.class)
    public ResponseEntity<Object> handleScoringInquiryNotFound(ScoringInquiryNotFoundException ex,
                                                                WebRequest request) {
        ErrorCode errorCode = ErrorCode.SCORING_INQUIRY_NOT_FOUND;
        String traceId = resolveTraceId();
        String path = resolvePath(request);

        log.warn("Scoring inquiry not found - traceId: {}, path: {}", traceId, path, ex);

        return ResponseEntity
                .status(errorCode.getHttpStatus())
                .body(buildErrorResponse(
                        errorCode,
                        traceId,
                        path,
                        ex.getFormattedDetails(),
                        null,
                        ex.getAdditionalProperties()
                ));
    }

    private ErrorResponse.ValidationError mapFieldError(FieldError fieldError) {
        return ErrorResponse.ValidationError.builder()
                .field(fieldError.getField())
                .value(fieldError.getRejectedValue())
                .message(fieldError.getDefaultMessage())
                .code(fieldError.getCode())
                .build();
    }

    private ErrorResponse.ValidationError mapObjectError(ObjectError error) {
        if (error instanceof FieldError fieldError) {
            return mapFieldError(fieldError);
        }

        return ErrorResponse.ValidationError.builder()
                .field(error.getObjectName())
                .message(error.getDefaultMessage())
                .code(error.getCode())
                .build();
    }

    private ErrorResponse.ValidationError mapResolvableError(MessageSourceResolvable resolvable) {
        if (resolvable instanceof ObjectError objectError) {
            return mapObjectError(objectError);
        }

        String message = resolvable.getDefaultMessage();
        String[] codes = resolvable.getCodes();
        String code = codes != null && codes.length > 0
                ? codes[0]
                : null;

        return ErrorResponse.ValidationError.builder()
                .message(message)
                .code(code)
                .build();
    }

    private ErrorResponse.ValidationError mapConstraintViolation(ConstraintViolation<?> violation) {
        String code = violation.getConstraintDescriptor() != null
                && violation.getConstraintDescriptor().getAnnotation() != null
                ? violation.getConstraintDescriptor().getAnnotation().annotationType().getSimpleName()
                : null;

        return ErrorResponse.ValidationError.builder()
                .field(violation.getPropertyPath() != null ? violation.getPropertyPath().toString() : null)
                .value(violation.getInvalidValue())
                .message(violation.getMessage())
                .code(code)
                .build();
    }

    private ErrorResponse buildErrorResponse(
            ErrorCode errorCode,
            String traceId,
            String path
    ) {
        return buildErrorResponse(errorCode, traceId, path, null, null, null);
    }

    private ErrorResponse buildErrorResponse(
            ErrorCode errorCode,
            String traceId,
            String path,
            List<ErrorResponse.ValidationError> validationErrors
    ) {
        return buildErrorResponse(errorCode, traceId, path, null, validationErrors, null);
    }

    private ErrorResponse buildErrorResponse(
            ErrorCode errorCode,
            String traceId,
            String path,
            String detailsOverride,
            List<ErrorResponse.ValidationError> validationErrors,
            Map<String, Object> additionalProperties
    ) {
        String details = detailsOverride != null ? detailsOverride : errorCode.formatDetails();

        return ErrorResponse.builder()
                .traceId(traceId)
                .status(errorCode.getHttpStatus().value())
                .reason(errorCode.getHttpStatus().getReasonPhrase())
                .code(errorCode.getCode())
                .message(errorCode.getMessage())
                .details(details)
                .path(path)
                .timestamp(Instant.now())
                .validationErrors(validationErrors)
                .additionalProperties(additionalProperties)
                .build();
    }

    private ErrorResponse buildErrorResponseWithStatus(
            ErrorCode errorCode,
            String traceId,
            String path,
            String detailsOverride,
            List<ErrorResponse.ValidationError> validationErrors,
            Map<String, Object> additionalProperties,
            int status,
            String reason
    ) {
        String details = detailsOverride != null ? detailsOverride : errorCode.formatDetails();

        return ErrorResponse.builder()
                .traceId(traceId)
                .status(status)
                .reason(reason)
                .code(errorCode.getCode())
                .message(errorCode.getMessage())
                .details(details)
                .path(path)
                .timestamp(Instant.now())
                .validationErrors(validationErrors)
                .additionalProperties(additionalProperties)
                .build();
    }

    private String resolveTraceId() {
        return MDC.get(RequestIdFilter.MDC_REQUEST_ID_KEY);
    }

    private String resolvePath(WebRequest request) {
        if (request instanceof ServletWebRequest servletWebRequest) {
            return servletWebRequest.getRequest().getRequestURI();
        }
        return request.getDescription(false);
    }

}



package com.azercell.akbintegrationservice.error.exceptions;

import com.azercell.akbintegrationservice.error.enums.ErrorCode;

public class AkbIntegrationException extends BaseException {

    public AkbIntegrationException(String operation, Throwable cause) {
        super(ErrorCode.AKB_INTEGRATION_ERROR, cause, operation);
        withProperty("operation", operation);
    }

    public AkbIntegrationException(String operation, Long batchId, Throwable cause) {
        super(ErrorCode.AKB_INTEGRATION_ERROR, cause, operation);
        withProperty("operation", operation);
        withProperty("batchId", batchId);
    }

}


package com.azercell.akbintegrationservice.error.exceptions;

import com.azercell.akbintegrationservice.error.enums.ErrorCode;
import lombok.Getter;

import java.util.HashMap;
import java.util.Map;

@Getter
public class BaseException extends RuntimeException {

    private final ErrorCode errorCode;
    private final Map<String, Object> additionalProperties;
    private final Object[] detailsParams;

    public BaseException(ErrorCode errorCode) {
        super(errorCode.getMessage());
        this.errorCode = errorCode;
        this.additionalProperties = new HashMap<>();
        this.detailsParams = new Object[0];
    }

    public BaseException(ErrorCode errorCode, Object... detailsParams) {
        super(errorCode.getMessage());
        this.errorCode = errorCode;
        this.additionalProperties = new HashMap<>();
        this.detailsParams = detailsParams;
    }

    public BaseException(ErrorCode errorCode, Throwable cause) {
        super(errorCode.getMessage(), cause);
        this.errorCode = errorCode;
        this.additionalProperties = new HashMap<>();
        this.detailsParams = new Object[0];
    }

    public BaseException(ErrorCode errorCode, Throwable cause, Object... detailsParams) {
        super(errorCode.getMessage(), cause);
        this.errorCode = errorCode;
        this.additionalProperties = new HashMap<>();
        this.detailsParams = detailsParams;
    }

    /**
     * Add additional context
     */
    public BaseException withProperty(String key, Object value) {
        this.additionalProperties.put(key, value);
        return this;
    }

    /**
     * Get formatted details with params
     */
    public String getFormattedDetails() {
        return errorCode.formatDetails(detailsParams);
    }

}


package com.azercell.akbintegrationservice.error.exceptions;

import com.azercell.akbintegrationservice.error.enums.ErrorCode;
import com.azercell.akbintegrationservice.error.model.ExternalServiceErrorResponse;
import lombok.Getter;

@Getter
public class ExternalServiceException extends BaseException {

    private final ExternalServiceErrorResponse externalServiceError;

    public ExternalServiceException(ExternalServiceErrorResponse externalServiceError) {
        super(resolveErrorCode(externalServiceError));
        this.externalServiceError = externalServiceError;
    }

    private static ErrorCode resolveErrorCode(ExternalServiceErrorResponse externalServiceError) {
        if (externalServiceError != null && externalServiceError.getErrorCode() != null) {
            return externalServiceError.getErrorCode();
        }
        return ErrorCode.AKB_INTEGRATION_ERROR;
    }

}


package com.azercell.akbintegrationservice.error.exceptions;

import com.azercell.akbintegrationservice.error.enums.ErrorCode;

public class IdempotencyConflictException extends BaseException {

    public IdempotencyConflictException(
            String idempotencyKey,
            String existingSubmissionId,
            String existingStatus
    ) {
        super(
                ErrorCode.SUBMISSION_ALREADY_EXISTS,
                idempotencyKey
        );

        withProperty("submissionId", existingSubmissionId);
        withProperty("status", existingStatus);
        withProperty("idempotencyKey", idempotencyKey);
    }
}


package com.azercell.akbintegrationservice.error.exceptions;

import com.azercell.akbintegrationservice.error.enums.ErrorCode;

public class ScoringInquiryNotFoundException extends BaseException {

    public ScoringInquiryNotFoundException(Long inquiryId) {
        super(
                ErrorCode.SCORING_INQUIRY_NOT_FOUND,
                inquiryId
        );
        withProperty("inquiryId", inquiryId);
    }
}


package com.azercell.akbintegrationservice.error.exceptions;

import com.azercell.akbintegrationservice.error.enums.ErrorCode;

public class SubmissionNotFoundException extends BaseException {

    public SubmissionNotFoundException(String submissionId) {
        super(
                ErrorCode.SUBMISSION_NOT_FOUND,
                submissionId
        );
        withProperty("submissionId", submissionId);
    }
}





                                                                Localization and i18n

1. Ilk once Resource Bundle yaratmaliyiq

# en (default)

# Demo (optional test endpoint)
HELLO=Hello
GREETINGS=Hello, {0}!

# API errors
error.account.not_found=Account with ID ''{0}'' was not found.
error.validation.failed=Validation failed
error.internal_server_error=Internal server error
error.request.body.not_readable=Request body is missing or malformed.

# Bean validation (CreateAccountRequest)
validation.name.required=name must not be blank
validation.email.required=email must not be blank
validation.email.invalid=email must be valid
validation.balance.required=balance must not be null
validation.balance.positive=balance must be greater than zero


# az

# Demo
HELLO=Salam
GREETINGS=Salam, {0}!

# API errors
error.account.not_found=''{0}'' ID-li hesab tapılmadı.
error.validation.failed=Validasiya uğursuz oldu
error.internal_server_error=Daxili server xətası
error.request.body.not_readable=Sorğu gövdəsi yoxdur və ya səhv formatdadır.

# Bean validation (CreateAccountRequest)
validation.name.required=ad boş ola bilməz
validation.email.required=email boş ola bilməz
validation.email.invalid=email düzgün formatda deyil
validation.balance.required=balans boş ola bilməz
validation.balance.positive=balans sıfırdan böyük olmalıdır


# ru

# Demo
HELLO=Привет
GREETINGS=Привет, {0}!

# API errors
error.account.not_found=Счёт с ID ''{0}'' не найден.
error.validation.failed=Ошибка валидации
error.internal_server_error=Внутренняя ошибка сервера
error.request.body.not_readable=Тело запроса отсутствует или имеет неверный формат.

# Bean validation (CreateAccountRequest)
validation.name.required=имя не должно быть пустым
validation.email.required=email не должен быть пустым
validation.email.invalid=некорректный email
validation.balance.required=баланс не должен быть пустым
validation.balance.positive=баланс должен быть больше нуля


2. Novbeti addim yaml faylinda kofiqurasiyani elave etmek:

spring:
  messages:
    basename: message
    encoding: UTF-8
  web:
    locale: en

bu addimda Spring-e deyirikki "tercumeler bu fayllardadir".


3. Novbeti addim bize LocaleResolver lazimdir, bu olmasa Spring bilmeyecek mesajlari hansi message faylindan oxusun. 

package guru.springframework.cruddemo.config;

import java.util.List;
import java.util.Locale;

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.servlet.LocaleResolver;
import org.springframework.web.servlet.i18n.AcceptHeaderLocaleResolver;

@Configuration
public class LocaleConfig {

    @Bean
    public LocaleResolver localeResolver() {
        AcceptHeaderLocaleResolver resolver = new AcceptHeaderLocaleResolver();
        resolver.setDefaultLocale(Locale.ENGLISH);
        resolver.setSupportedLocales(List.of(
                Locale.forLanguageTag("az"),
                Locale.forLanguageTag("ru"),
                Locale.ENGLISH));
        return resolver;
    }

}


4. Novbeti addim ise bize MessageService lazimdir:

package guru.springframework.cruddemo.service.impl;

import java.util.Locale;

import org.springframework.context.MessageSource;
import org.springframework.stereotype.Service;
import org.springframework.web.context.request.WebRequest;

import lombok.RequiredArgsConstructor;

@Service
@RequiredArgsConstructor
public class TranslatorServiceImpl {

    private final MessageSource messageSource;

    public String translate(String key, Locale locale, Object... args) {
        return messageSource.getMessage(key, args, key, locale);
    }

    public String translate(String key, WebRequest request, Object... args) {
        return translate(key, request.getLocale(), args);
    }

}


5. Novbeti addim ErroCode klasina messageKey field-ini elave etmek:

package guru.springframework.cruddemo.error;

import java.text.MessageFormat;
import java.util.Arrays;

import org.springframework.http.HttpStatus;

import com.fasterxml.jackson.annotation.JsonCreator;
import com.fasterxml.jackson.annotation.JsonValue;

import lombok.Getter;
import lombok.RequiredArgsConstructor;

@Getter
@RequiredArgsConstructor
public enum ErrorCode {

    VALIDATION_FAILED(
            "VALIDATION_FAILED",
            "error.validation.failed",
            "Validation failed",
            "One or more fields failed validation.",
            HttpStatus.BAD_REQUEST),
    METHOD_VALIDATION_FAILED(
            "METHOD_VALIDATION_FAILED",
            "error.method.validation.failed",
            "Method validation failed",
            "One or more method parameters failed validation.",
            HttpStatus.BAD_REQUEST),
    CONSTRAINT_VIOLATION(
            "CONSTRAINT_VIOLATION",
            "error.constraint.violation",
            "Constraint violation",
            "One or more constraints were violated.",
            HttpStatus.BAD_REQUEST),
    REQUEST_BODY_NOT_READABLE(
            "REQUEST_BODY_NOT_READABLE",
            "error.request.body.not_readable",
            "Malformed request body",
            "Request body is missing or malformed.",
            HttpStatus.BAD_REQUEST),
    MISSING_REQUEST_PARAMETER(
            "MISSING_REQUEST_PARAMETER",
            "error.missing.request.parameter",
            "Missing request parameter",
            "A required request parameter is missing.",
            HttpStatus.BAD_REQUEST),
    TYPE_MISMATCH(
            "TYPE_MISMATCH",
            "error.type.mismatch",
            "Type mismatch",
            "Request parameter type is invalid.",
            HttpStatus.BAD_REQUEST),
    BAD_REQUEST(
            "BAD_REQUEST",
            "error.bad.request",
            "Bad request",
            "Request is malformed or contains invalid data.",
            HttpStatus.BAD_REQUEST),
    AKB_INTEGRATION_ERROR(
            "AKB_INTEGRATION_ERROR",
            "error.akb.integration.error",
            "AKB integration error",
            "AKB integration failed during {0}.",
            HttpStatus.SERVICE_UNAVAILABLE),
    INTERNAL_SERVER_ERROR(
            "INTERNAL_SERVER_ERROR",
            "error.internal_server_error",
            "Internal server error",
            "An unexpected error occurred.",
            HttpStatus.INTERNAL_SERVER_ERROR),
    SUBMISSION_ALREADY_EXISTS(
            "IDEMPOTENCY_KEY_EXISTS",
            "error.submission.already.exists",
            "Submission with this idempotency key already exists",
            "A credit submission with idempotency key ''{0}'' has already been processed. This is a duplicate request. If you need to submit a new credit, please generate a new idempotency key.",
            HttpStatus.CONFLICT),
    SUBMISSION_NOT_FOUND(
            "SUBMISSION_NOT_FOUND",
            "error.submission.not_found",
            "Submission not found",
            "Submission with ID ''{0}'' was not found.",
            HttpStatus.NOT_FOUND),
    SCORING_INQUIRY_NOT_FOUND(
            "SCORING_INQUIRY_NOT_FOUND",
            "error.scoring.inquiry.not_found",
            "Scoring inquiry not found",
            "Scoring inquiry with ID ''{0}'' was not found.",
            HttpStatus.NOT_FOUND),
    ACCOUNT_NOT_FOUND(
            "ACCOUNT_NOT_FOUND",
            "error.account.not_found",
            "Account not found",
            "Account with ID ''{0}'' was not found.",
            HttpStatus.NOT_FOUND),

    UNKNOWN(
            "UNKNOWN",
            "error.unknown",
            "Unknown error",
            "An unrecognized error code was received.",
            HttpStatus.INTERNAL_SERVER_ERROR);

    @Getter(onMethod_ = @JsonValue)
    private final String code;
    private final String messageKey;
    private final String message;
    private final String detailsTemplate;
    private final HttpStatus httpStatus;

    public String formatDetails(Object... params) {
        if (params == null || params.length == 0) {
            return this.detailsTemplate;
        }
        return MessageFormat.format(this.detailsTemplate, params);
    }

    @JsonCreator
    public static ErrorCode fromCode(String value) {
        if (value == null || value.isBlank()) {
            return null;
        }
        return Arrays.stream(values())
                .filter(c -> c.code.equals(value))
                .findFirst()
                .orElse(UNKNOWN);
    }
}



6. Validasiya (field error) mesajlarini i18n ile birleshdirmek. 

package guru.springframework.cruddemo.dto;

import java.math.BigDecimal;

import jakarta.validation.constraints.Email;
import jakarta.validation.constraints.NotBlank;
import jakarta.validation.constraints.NotNull;
import jakarta.validation.constraints.Positive;
import lombok.Data;

@Data
public class CreateAccountRequest {

    @NotBlank(message = "{validation.name.required}")
    private String name;

    @NotBlank(message = "{validation.email.required}")
    @Email(message = "{validation.email.invalid}")
    private String email;

    @NotNull(message = "{validation.balance.required}")
    @Positive(message = "{validation.balance.positive}")
    private BigDecimal balance;

}


ve ValidationConfig quraq:

package guru.springframework.cruddemo.config;

import org.springframework.context.MessageSource;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.validation.beanvalidation.LocalValidatorFactoryBean;

@Configuration
public class ValidationConfig {

    @Bean
    public LocalValidatorFactoryBean defaultValidator(MessageSource messageSource) {
        LocalValidatorFactoryBean factoryBean = new LocalValidatorFactoryBean();
        factoryBean.setValidationMessageSource(messageSource);
        return factoryBean;
    }

}


sonra ise GlobalExceptionHandler-de tetbiq etmek:


package guru.springframework.cruddemo.error;

import java.time.Instant;
import java.util.List;
import java.util.Locale;

import org.springframework.http.ResponseEntity;
import org.springframework.http.converter.HttpMessageNotReadableException;
import org.springframework.web.bind.MethodArgumentNotValidException;
import org.springframework.web.bind.annotation.ExceptionHandler;
import org.springframework.web.bind.annotation.RestControllerAdvice;
import org.springframework.web.context.request.ServletWebRequest;
import org.springframework.web.context.request.WebRequest;

import guru.springframework.cruddemo.service.impl.TranslatorServiceImpl;
import lombok.RequiredArgsConstructor;
import lombok.extern.slf4j.Slf4j;

@Slf4j
@RestControllerAdvice
@RequiredArgsConstructor
public class GlobalExceptionHandler {

    private final TranslatorServiceImpl translator;

    @ExceptionHandler(BaseException.class)
    public ResponseEntity<ErrorResponse> handleBaseException(BaseException ex, WebRequest request) {
        Locale locale = request.getLocale();
        ErrorResponse body = ErrorResponse.builder()
                .status(ex.getHttpStatus().value())
                .code(ex.getErrorCode().getCode())
                .message(translator.translate(
                        ex.getErrorCode().getMessageKey(), locale, ex.getDetailsParams()))
                .timestamp(Instant.now())
                .path(requestPath(request))
                .build();
        return ResponseEntity.status(ex.getHttpStatus()).body(body);
    }

    @ExceptionHandler(MethodArgumentNotValidException.class)
    public ResponseEntity<ErrorResponse> handleMethodArgumentNotValid(
            MethodArgumentNotValidException ex,
            WebRequest request) {
        Locale locale = request.getLocale();
        ErrorCode code = ErrorCode.VALIDATION_FAILED;
        List<FieldErrorDto> fieldErrors = ex.getBindingResult().getFieldErrors().stream()
                .map(fieldError -> FieldErrorDto.builder()
                        .field(fieldError.getField())
                        .message(resolveFieldMessage(fieldError.getDefaultMessage(), locale))
                        .build())
                .toList();
        ErrorResponse body = ErrorResponse.builder()
                .status(code.getHttpStatus().value())
                .code(code.getCode())
                .message(translator.translate(code.getMessageKey(), locale))
                .timestamp(Instant.now())
                .path(requestPath(request))
                .fieldErrors(fieldErrors)
                .build();
        return ResponseEntity.status(code.getHttpStatus()).body(body);
    }

    @ExceptionHandler(HttpMessageNotReadableException.class)
    public ResponseEntity<ErrorResponse> handleHttpMessageNotReadable(
            HttpMessageNotReadableException ex,
            WebRequest request) {
        Locale locale = request.getLocale();
        ErrorCode code = ErrorCode.REQUEST_BODY_NOT_READABLE;
        ErrorResponse body = ErrorResponse.builder()
                .status(code.getHttpStatus().value())
                .code(code.getCode())
                .message(translator.translate(code.getMessageKey(), locale))
                .timestamp(Instant.now())
                .path(requestPath(request))
                .build();
        return ResponseEntity.status(code.getHttpStatus()).body(body);
    }

    @ExceptionHandler(Exception.class)
    public ResponseEntity<ErrorResponse> handleUnexpected(Exception ex, WebRequest request) {
        log.error("Unhandled exception", ex);
        Locale locale = request.getLocale();
        ErrorCode code = ErrorCode.INTERNAL_SERVER_ERROR;
        ErrorResponse body = ErrorResponse.builder()
                .status(code.getHttpStatus().value())
                .code(code.getCode())
                .message(translator.translate(code.getMessageKey(), locale))
                .timestamp(Instant.now())
                .path(requestPath(request))
                .build();
        return ResponseEntity.status(code.getHttpStatus()).body(body);
    }

    private String resolveFieldMessage(String defaultMessage, Locale locale) {
        if (defaultMessage == null || defaultMessage.isBlank()) {
            return defaultMessage;
        }
        if (defaultMessage.startsWith("{") && defaultMessage.endsWith("}")) {
            String key = defaultMessage.substring(1, defaultMessage.length() - 1);
            return translator.translate(key, locale);
        }
        return defaultMessage;
    }

    private static String requestPath(WebRequest request) {
        if (request instanceof ServletWebRequest servletWebRequest) {
            return servletWebRequest.getRequest().getRequestURI();
        }
        return request.getDescription(false);
    }

}










==========================================================================

package com.azercell.akbintegrationservice.client.akb.decoder;

import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;

@Data
@NoArgsConstructor
@AllArgsConstructor
public class AkbErrorResponse {

    private String timestamp;
    private Integer status;
    private String error;
    private String message;
    private String path;

}


package com.azercell.akbintegrationservice.client.akb.decoder;

import com.azercell.akbintegrationservice.error.enums.ErrorCode;
import com.azercell.akbintegrationservice.error.exceptions.ExternalServiceException;
import com.azercell.akbintegrationservice.error.model.ExternalServiceErrorResponse;
import com.fasterxml.jackson.databind.ObjectMapper;
import feign.Response;
import feign.Util;
import feign.codec.ErrorDecoder;
import lombok.extern.slf4j.Slf4j;

import java.io.IOException;
import java.net.URI;
import java.time.Instant;

@Slf4j
public class AkbErrorDecoder implements ErrorDecoder {

    private final ObjectMapper objectMapper;

    public AkbErrorDecoder(ObjectMapper objectMapper) {
        this.objectMapper = objectMapper;
    }

    @Override
    public Exception decode(String methodKey, Response response) {
        String body = readBody(response);
        ExternalServiceErrorResponse externalError = mapExternalError(response, body);
        return new ExternalServiceException(externalError);
    }

    private ExternalServiceErrorResponse mapExternalError(Response response, String body) {
        String path = resolvePath(response);
        String timestamp = Instant.now().toString();

        if (body != null && !body.isBlank()) {
            try {
                AkbErrorResponse akbError = objectMapper.readValue(body, AkbErrorResponse.class);
                return ExternalServiceErrorResponse.builder()
                        .timestamp(akbError.getTimestamp() != null ? akbError.getTimestamp() : timestamp)
                        .status(akbError.getStatus() != null ? akbError.getStatus() : response.status())
                        .error(akbError.getError())
                        .message(akbError.getMessage())
                        .path(akbError.getPath() != null ? akbError.getPath() : path)
                        .errorCode(ErrorCode.AKB_INTEGRATION_ERROR)
                        .build();
            } catch (Exception ex) {
                log.error("Failed to parse AKB error response body, falling back", ex);
                // Fall through to fallback mapping
            }
        }

        return ExternalServiceErrorResponse.builder()
                .timestamp(timestamp)
                .status(response.status())
                .error(response.reason())
                .message(body)
                .path(path)
                .errorCode(ErrorCode.AKB_INTEGRATION_ERROR)
                .build();
    }

    private String resolvePath(Response response) {
        if (response.request() == null || response.request().url() == null) {
            return null;
        }
        try {
            return URI.create(response.request().url()).getPath();
        } catch (Exception ignored) {
            return response.request().url();
        }
    }

    private String readBody(Response response) {
        if (response.body() == null) {
            return null;
        }
        try {
            return Util.toString(response.body().asReader(Util.UTF_8));
        } catch (IOException ignored) {
            return null;
        }
    }

}






























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