Error Handling

Comprehensive error handling patterns for moclojer - validation errors, not found, server errors, and consistent error response formats. Build robust APIs.

Learn to create consistent, informative error responses in moclojer.

📋 Common Error Patterns

404 Not Found

- endpoint:
    method: GET
    path: /users/999
    response:
      status: 404
      headers:
        Content-Type: application/json
      body: >
        {
          "error": "Not Found",
          "message": "User with ID 999 not found",
          "code": "USER_NOT_FOUND",
          "timestamp": "{{now}}"
        }

400 Bad Request

- endpoint:
    method: POST
    path: /users/invalid
    response:
      status: 400
      headers:
        Content-Type: application/json
      body: >
        {
          "error": "Bad Request",
          "message": "Invalid request data",
          "code": "INVALID_REQUEST"
        }

422 Validation Error

- endpoint:
    method: POST
    path: /users/validation-error
    response:
      status: 422
      headers:
        Content-Type: application/json
      body: >
        {
          "error": "Validation Failed",
          "code": "VALIDATION_ERROR",
          "errors": [
            {
              "field": "email",
              "message": "Invalid email format"
            },
            {
              "field": "password",
              "message": "Password too short"
            }
          ]
        }

401 Unauthorized

- endpoint:
    method: GET
    path: /protected/unauthorized
    response:
      status: 401
      headers:
        Content-Type: application/json
      body: >
        {
          "error": "Unauthorized",
          "message": "Authentication required",
          "code": "AUTH_REQUIRED"
        }

403 Forbidden

- endpoint:
    method: DELETE
    path: /admin/forbidden
    response:
      status: 403
      headers:
        Content-Type: application/json
      body: >
        {
          "error": "Forbidden",
          "message": "Insufficient permissions",
          "code": "FORBIDDEN"
        }

500 Internal Server Error

- endpoint:
    method: GET
    path: /error/server
    response:
      status: 500
      headers:
        Content-Type: application/json
      body: >
        {
          "error": "Internal Server Error",
          "message": "An unexpected error occurred",
          "code": "INTERNAL_ERROR",
          "request_id": "req_{{now|timestamp}}"
        }

✅ Best Practices

Consistent Format:

{
  "error": "Error Type",
  "message": "Human-readable message",
  "code": "MACHINE_READABLE_CODE",
  "timestamp": "2024-01-15T10:30:00Z",
  "request_id": "req_123"
}

Include:

• ✅ Error type

• ✅ Readable message

• ✅ Machine-readable code

• ✅ Timestamp

• ✅ Request ID (for tracking)

Field-Level Errors:

{
  "error": "Validation Failed",
  "errors": [
    {"field": "email", "message": "Required"},
    {"field": "age", "message": "Must be positive"}
  ]
}

📚 See Also

• Response Structure

• Authentication Mock

• CRUD Operations