Applicazione dei vincoli

Pulizia dei dati in Java

Dennis Lee

Software Engineer

Controllo qualità dei dati

Annotazioni di validazione: controllo qualità dei dati
Errori: paesi mancanti, importi non validi, scatole spedite negative
Refusi: 1000 scatole invece di 100

Venditore	Paese	Prodotto	Data	Importo	Scatole spedite
James Rudeforth	UK	Mint Chip Choco	4-gen-22	$5320	100
Van Tuxwell	India	85% Dark Bars	1-ago-22	$7896	94
Gigi Bohling	US	Peanut Butter Cubes	7-lug-22	$4501	91

Annotazioni di validazione di base

import jakarta.validation.constraints.NotNull;     // Import rules for empty fields
import jakarta.validation.constraints.Size;        // Import rules for string length

public class ChocolateSale {
    @NotNull(message = "Salesperson cannot be empty")
    private String salesperson;


    @NotNull(message = "Country cannot be empty")  // Multiple rules can be stacked
    @Size(min = 2, max = 50)                       // Enforces country name length
    private String country;


    @NotNull(message = "Product cannot be empty")
    private String product;
}

Vincoli numerici

import jakarta.validation.constraints.Max;
import jakarta.validation.constraints.Min;

// We will show message outputs later
public class ChocolateSale {
    @Min(value = 0, message = "Sales amount must be positive")
    private Double amount;


    @Min(value = 1, message = "Must ship at least 1 box")
    @Max(value = 1000, message = "Cannot ship more than 1000 boxes")
    private Integer boxesShipped;
}

Import per applicare i vincoli

// Stores unique validation errors (no duplicates)
import java.util.Set;
// Holds details about a single validation error (field, message, etc.)
import jakarta.validation.ConstraintViolation;
// Entry point for creating validators
import jakarta.validation.Validation;
// Checks data against rules
import jakarta.validation.Validator;
// Creates configured validators
import jakarta.validation.ValidatorFactory;
// Thrown when validation fails
import jakarta.validation.ConstraintViolationException;

Implementare il validator

class SalesValidator {
    // Create tools for checking our data
    private static final ValidatorFactory factory = Validation.buildDefaultValidatorFactory();


    // Get a validator to check sales records
    private static final Validator validator = factory.getValidator();


    public static Set<ConstraintViolation<ChocolateSale>> validateSale(ChocolateSale sale) {
        // Check sale record and return any problems found
        return validator.validate(sale);
    }
}

Gestire i risultati di validazione

public class Main {
    public static void main(String[] args) {
        // Create sale with some invalid data (null country, negative amount)
        ChocolateSale sale = new ChocolateSale("James Rudeforth", null, "Mint Chip Choco",
                LocalDate.parse("2022-01-04"), -5320.0, 1500);


        // Check sale for validation violations
        Set<ConstraintViolation<ChocolateSale>> violations = SalesValidator.validateSale(sale);
        // Print each validation error message
        violations.forEach(violation -> System.out.println(violation.getMessage()));

        // If any violations found, throw exception
        if (!violations.isEmpty()) throw new ConstraintViolationException(violations);
    }
}

Output di validazione

Country cannot be empty
Sales amount must be positive
Cannot ship more than 1000 boxes


Exception in thread "main" 
jakarta.validation.ConstraintViolationException

La validazione evita errori costosi

@NotNull, @Size, @Min e @Max intercettano presto gli errori
Applica la validazione a problemi di business generali
Prima difesa contro errori di dati costosi

Fave di cacao setacciate in fabbrica

Passiamo alla pratica !

Pulizia dei dati in Java