Coding ManBean Validation的约束组合
Contents
1. 概述
在本教程中，我们将讨论Bean Validation 的约束组合。
将多个约束分组在单个自定义注解下可以减少代码重复并提高可读性。我们将看到如何创建组合约束以及如何根据我们的需要自定义它们。
对于代码示例，我们将具有与Java Bean Validation Basics 中相同的依赖关系。
2. 理解问题
首先，让我们熟悉一下数据模型。我们将在本文的大部分示例中使用Account类：
public class Account {
@NotNull
@Pattern(regexp = ".*\\d.*", message = "must contain at least one numeric character")
@Length(min = 6, max = 32, message = "must have between 6 and 32 characters")
private String username;
@NotNull
@Pattern(regexp = ".*\\d.*", message = "must contain at least one numeric character")
@Length(min = 6, max = 32, message = "must have between 6 and 32 characters")
private String nickname;
@NotNull
@Pattern(regexp = ".*\\d.*", message = "must contain at least one numeric character")
@Length(min = 6, max = 32, message = "must have between 6 and 32 characters")
private String password;
// getters and setters
}
我们可以注意到*@NotNull*、@Pattern和*@Length*约束对三个字段中的每一个都重复。
此外，如果这些字段之一存在于来自不同层的多个类中，则约束应该匹配——导致更多的代码重复。
例如，我们可以想象在 DTO 对象和*@Entity模型中拥有username*字段。
3. 创建组合约束
我们可以通过将三个约束分组到具有合适名称的自定义注解下来避免代码重复：
@NotNull
@Pattern(regexp = ".*\\d.*", message = "must contain at least one numeric character")
@Length(min = 6, max = 32, message = "must have between 6 and 32 characters")
@Target({ METHOD, FIELD, ANNOTATION_TYPE, CONSTRUCTOR, PARAMETER })
@Retention(RUNTIME)
@Documented
@Constraint(validatedBy = {})
public @interface ValidAlphanumeric {
String message() default "field should have a valid length and contain numeric character(s).";
Class<?>[] groups() default {};
Class<? extends Payload>[] payload() default {};
}
因此，我们现在可以使用*@ValidAlphanumeric来验证Account*字段：
public class Account {
@ValidAlphanumeric
private String username;
@ValidAlphanumeric
private String password;
@ValidAlphanumeric
private String nickname;
// getters and setters
}
因此，我们可以测试*@ValidAlphanumeric*注解，并期望违反的约束与违反的约束一样多。
例如，如果我们将username设置为*“john”*，我们应该会遇到两次违规，因为它太短并且不包含数字字符：
@Test
public void whenUsernameIsInvalid_validationShouldReturnTwoViolations() {
Account account = new Account();
account.setPassword("valid_password123");
account.setNickname("valid_nickname123");
account.setUsername("john");
Set<ConstraintViolation<Account>> violations = validator.validate(account);
assertThat(violations).hasSize(2);
}
4. 使用*@ReportAsSingleViolation*
另一方面，我们可能希望验证为整个组返回单个ConstraintViolation。
为此，我们必须使用*@ReportAsSingleViolation*注解我们的组合约束：
@NotNull
@Pattern(regexp = ".*\\d.*", message = "must contain at least one numeric character")
@Length(min = 6, max = 32, message = "must have between 6 and 32 characters")
@Target({ METHOD, FIELD, ANNOTATION_TYPE, CONSTRUCTOR, PARAMETER })
@Retention(RUNTIME)
@Documented
@Constraint(validatedBy = {})
@ReportAsSingleViolation
public @interface ValidAlphanumericWithSingleViolation {
String message() default "field should have a valid length and contain numeric character(s).";
Class<?>[] groups() default {};
Class<? extends Payload>[] payload() default {};
}
之后，我们可以使用password字段测试我们的新注解，并预计会出现一次违规：
@Test
public void whenPasswordIsInvalid_validationShouldReturnSingleViolation() {
Account account = new Account();
account.setUsername("valid_username123");
account.setNickname("valid_nickname123");
account.setPassword("john");
Set<ConstraintViolation<Account>> violations = validator.validate(account);
assertThat(violations).hasSize(1);
}
5. 布尔约束组合
到目前为止，验证仅在所有组合约束都有效时才通过。发生这种情况是因为ConstraintComposition值默认为CompositionType.AND。**
但是，如果我们想检查是否存在至少一个有效约束，我们可以更改此行为。
为此，我们需要将ConstraintComposition切换为CompositionType：
@Pattern(regexp = ".*\\d.*", message = "must contain at least one numeric character")
@Length(min = 6, max = 32, message = "must have between 6 and 32 characters")
@Target({ METHOD, FIELD, ANNOTATION_TYPE, CONSTRUCTOR, PARAMETER })
@Retention(RUNTIME)
@Documented
@Constraint(validatedBy = {})
@ConstraintComposition(CompositionType.OR)
public @interface ValidLengthOrNumericCharacter {
String message() default "field should have a valid length or contain numeric character(s).";
Class<?>[] groups() default {};
Class<? extends Payload>[] payload() default {};
}
例如，给定一个太短但至少包含一个数字字符的值，则不应存在违规。
让我们使用模型中的nickname字段来测试这个新注解：
@Test
public void whenNicknameIsTooShortButContainsNumericCharacter_validationShouldPass() {
Account account = new Account();
account.setUsername("valid_username123");
account.setPassword("valid_password123");
account.setNickname("doe1");
Set<ConstraintViolation<Account>> violations = validator.validate(account);
assertThat(violations).isEmpty();
}
同样，我们可以使用CompositionType。ALL_FALSE如果我们想确保约束失败。
6. 使用组合约束进行方法验证
此外，我们可以使用组合约束作为方法约束 。
为了验证方法的返回值，我们只需将*@SupportedValidationTarget(ValidationTarget.ANNOTATED_ELEMENT)*添加到组合约束中：
@NotNull
@Pattern(regexp = ".*\\d.*", message = "must contain at least one numeric character")
@Length(min = 6, max = 32, message = "must have between 6 and 32 characters")
@Target({ METHOD, FIELD, ANNOTATION_TYPE, CONSTRUCTOR, PARAMETER })
@Retention(RUNTIME)
@Documented
@Constraint(validatedBy = {})
@SupportedValidationTarget(ValidationTarget.ANNOTATED_ELEMENT)
public @interface AlphanumericReturnValue {
String message() default "method return value should have a valid length and contain numeric character(s).";
Class<?>[] groups() default {};
Class<? extends Payload>[] payload() default {};
}
为了举例说明这一点，我们将使用getAnInvalidAlphanumericValue方法，该方法使用我们的自定义约束进行注解：
@Component
@Validated
public class AccountService {
@AlphanumericReturnValue
public String getAnInvalidAlphanumericValue() {
return "john";
}
}
现在，让我们调用这个方法并期望抛出一个ConstraintViolationException：
@Test
public void whenMethodReturnValuesIsInvalid_validationShouldFail() {
assertThatThrownBy(() -> accountService.getAnInvalidAlphanumericValue())
.isInstanceOf(ConstraintViolationException.class)
.hasMessageContaining("must contain at least one numeric character")
.hasMessageContaining("must have between 6 and 32 characters");
}