Yavi用一行代码实现各种复杂验证

yavi特性如下：

• 类型安全的约束，不支持的约束不能应用于错误类型

• 流畅且直观的API

• 适用于任何对象的约束。包括Java Beans、Records、Protocol Buffers、Immutables等

• 众多强大的内置约束

• 易于自定义约束

• 分组验证，条件验证

• 在创建对象前对参数进行验证

• 支持API，以及结合验证结果和验证器的功能，融入了函数式编程的概念

<dependency>
  <groupId>am.ik.yavi</groupId>
  <artifactId>yavi</artifactId>
  <version>0.14.4</version>
</dependency>

2.2 定义和获取核心验证器实例

可以通过am.ik.yavi.builder.ValidatorBuilder来定义和获取核心验证器am.ik.yavi.core.Validator。如下示例：

Validator<User> validator = ValidatorBuilder.<User>of()
  .constraint(User::getName, "name", c -> c.notEmpty())
  .constraint(User::getIdNo, "idNo", c -> c.notNull().greaterThanOrEqual(2).lessThanOrEqual(14))
  .constraint(User::getAge, "age", c -> c.greaterThanOrEqual(18)).build()

该示例，我们对User对象定义了验证器Validator，分别对name，idno，age三个字段定义了约束条件。

使用示例：

@Test
public void testUser() {
  User user = new User("", "xxx", 17) ;
  ConstraintViolations violations = User.validator.validate(user) ;
  if (!violations.isValid()) {
    violations.forEach(violation -> {
      System.err.printf("字段【%s】不正确, 错误信息: %s%n", violation.name(), violation.message()) ;
    });
  }
}

2.3 嵌套对象验证

可以使用nest方法将约束应用于嵌套字段。你可以委托给嵌套字段的Validator进行验证，也可以在嵌套字段内部定义一组约束。如下示例：

// 实体对象定义如下
public class Address {
  private City city;
  private Country country;
  // getters, setters, construct
}
public class City {
  private String name ;
    // getters, setters, construct
}
public class Country {
  private String name ;
  // getters, setters, construct
}

public interface AddressValidator {
  Validator<Country> countryValidator = ValidatorBuilder.<Country> of()
      .constraint(Country::getName, "name", c -> c.notEmpty().greaterThanOrEqual(2))
      .build();
  Validator<City> cityValidator = ValidatorBuilder.<City> of()
      .constraint(City::getName, "name", c -> c.notEmpty())
      .build();
  Validator<Address> validator = ValidatorBuilder.<Address> of()
      .nest(Address::getCountry, "country", countryValidator)
      .nest(Address::getCity, "city", cityValidator)
      .build() ;
  
  Validator<Address> validator_2 = ValidatorBuilder.<Address> of()
      .nest(Address::getCountry, "country",
          b -> b.constraint(Country::getName, "name", c -> c.notEmpty()))
      .nest(Address::getCity, "city",
          b -> b.constraint(City::getName, "name", c -> c.notEmpty()))
      .build();
}

@Test
public void testAddressValidator() {
  City city = new City() ;
  Country country = new Country("X") ;
  Address address = new Address(city, country) ;
  ConstraintViolations violations = AddressValidator.validator.validate(address) ;
  if (!violations.isValid()) {
    violations.forEach(violation -> {
      System.err.printf("字段【%s】不正确, 错误信息: %s%n", violation.name(), violation.message()) ;
    });
  }
}

2.4 集合验证

你可以使用forEach方法将约束应用于Collection / Map/ Array中的每个元素。与嵌套字段类似，可以委托给每个元素的Validator进行验证，也可以在元素内部定义一组约束。如下示例：

public class Person {
  private final String name ;
  // getters, setters, construct
}
public class PersonVO {
  private final List<Person> persons;
  public PersonVO(List<Person> persons) {
    this.persons = persons;
  }
  public List<Person> getPersons() {
    return persons ;
  }
}

public interface PersonValidator {
  Validator<Person> personValidator = ValidatorBuilder.<Person> of()
      .constraint(Person::getName, "name", c -> c.notEmpty().greaterThanOrEqual(2))
      .build();
  Validator<PersonVO> validator = ValidatorBuilder.<PersonVO> of()
      .forEach(PersonVO::getPersons, "persons", personValidator)
      .build();
}

参考:

抛弃@Valid注解！Yavi用一行代码实现各种复杂验证