इनपुट सत्यापन और त्रुटि प्रबंधन

package com.coddykit.dto;

import jakarta.validation.constraints.DecimalMin;
import jakarta.validation.constraints.NotBlank;
import jakarta.validation.constraints.NotNull;
import jakarta.validation.constraints.Size;

public class ProductRequest {

    @NotBlank(message = "Name cannot be empty")
    @Size(min = 3, max = 50, message = "Name must be between 3 and 50 characters")
    private String name;

    @NotNull(message = "Price cannot be null")
    @DecimalMin(value = "0.01", message = "Price must be greater than 0")
    private Double price;

    @NotBlank(message = "Description cannot be empty")
    @Size(max = 200, message = "Description cannot exceed 200 characters")
    private String description;

    // Getters and Setters (omitted for brevity in snippet)
    public String getName() { return name; }
    public void setName(String name) { this.name = name; }
    public Double getPrice() { return price; }
    public void setPrice(Double price) { this.price = price; }
    public String getDescription() { return description; }
    public void setDescription(String description) { this.description = description; }
}

import com.coddykit.dto.ProductRequest;
import jakarta.validation.ConstraintViolation;
import jakarta.validation.Validation;
import jakarta.validation.Validator;
import jakarta.validation.ValidatorFactory;
import java.util.Set;

public class Main {
    public static void main(String[] args) {
        ValidatorFactory factory = Validation.buildDefaultValidatorFactory();
        Validator validator = factory.getValidator();

        ProductRequest invalidProduct = new ProductRequest();
        invalidProduct.setName("  "); // Too short, blank
        invalidProduct.setPrice(-5.0); // Less than 0.01
        invalidProduct.setDescription("Short");

        Set<ConstraintViolation<ProductRequest>> violations =
            validator.validate(invalidProduct);

        if (!violations.isEmpty()) {
            System.out.println("Validation Errors:");
            for (ConstraintViolation<ProductRequest> violation : violations) {
                System.out.println("- " + violation.getMessage());
            }
        } else {
            System.out.println("Product is valid!");
        }
    }
}

package com.coddykit.controller;

import com.coddykit.dto.ProductRequest;
import jakarta.validation.Valid;
import org.springframework.http.HttpStatus;
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.RestController;

@RestController
public class ProductController {

    @PostMapping("/products")
    public ResponseEntity<String> createProduct(@Valid @RequestBody ProductRequest productRequest) {
        // If validation passes, this code executes
        System.out.println("Received valid product: " + productRequest.getName());
        return new ResponseEntity<>("Product created successfully!", HttpStatus.CREATED);
    }
}

package com.coddykit.exception;

import org.springframework.http.HttpStatus;
import org.springframework.http.ResponseEntity;
import org.springframework.validation.FieldError;
import org.springframework.web.bind.MethodArgumentNotValidException;
import org.springframework.web.bind.annotation.ControllerAdvice;
import org.springframework.web.bind.annotation.ExceptionHandler;

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

@ControllerAdvice
public class GlobalExceptionHandler {

    @ExceptionHandler(MethodArgumentNotValidException.class)
    public ResponseEntity<Map<String, String>> handleValidationExceptions(
            MethodArgumentNotValidException ex) {
        Map<String, String> errors = new HashMap<>();
        ex.getBindingResult().getAllErrors().forEach(error -> {
            String fieldName = ((FieldError) error).getField();
            String errorMessage = error.getDefaultMessage();
            errors.put(fieldName, errorMessage);
        });
        return new ResponseEntity<>(errors, HttpStatus.BAD_REQUEST);
    }
}