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DTO Conversion (Inbound)

The Inbound DTO Conversion responsibility converts incoming JSON to Data Transfer Objects (DTOs) automatically via Jackson.

Inbound Conversion

HTTP request bodies are automatically deserialized from JSON to DTOs:

• HTTP request body is JSON string
• Spring calls Jackson deserializer
• JSON → DTO object mapping
• Field validation applied (if @Valid annotation present)
• DTO passed to controller method

Jackson Deserialization

Benefits: - Decouples API contract from internal domain models - Enables API versioning and forward compatibility - Only API-relevant fields are mapped - Type safety at compile time

Inbound Conversion Example

@PostMapping
public ResponseEntity<SupplierDTO> create(
    @Valid @RequestBody CreateSupplierDTO dto  // Jackson deserializes JSON → DTO
) {
    // dto is now a typed Java object with validated fields
    SupplierDTO created = supplierService.create(dto);
    return ResponseEntity.status(HttpStatus.CREATED).body(created);
}

HTTP Request:

POST /api/suppliers
Content-Type: application/json

{
    "name": "ACME Corp",
    "contactName": "John Doe",
    "contactEmail": "john@acme.com",
    "phoneNumber": "5551234567",
    "minOrderQuantity": 10
}

Jackson Processing:

JSON String
    ↓
Jackson ObjectMapper
    ↓
@NotBlank validation on fields
    ↓
CreateSupplierDTO object (strongly typed)
    ↓
Controller method executes

DTO Annotations for Deserialization

@Data
@Builder
public class CreateSupplierDTO {
    
    @JsonProperty("name")  // Optional: explicit JSON field name
    @NotBlank
    private String name;
    
    @JsonIgnore  // Optional: exclude field from deserialization
    private String internalField;
    
    @JsonFormat(pattern = "yyyy-MM-dd")  // Optional: date format
    private LocalDate createdDate;
}

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