[已解決] UnexpectedTypeException - 找不到約束驗證器 · HowToDoInJava 中文系列教程

# [已解決] `UnexpectedTypeException` - 找不到約束驗證器 > 原文： [https://howtodoinjava.com/hibernate/unexpectedtypeexception-error/](https://howtodoinjava.com/hibernate/unexpectedtypeexception-error/) 在使用 Hiberate 驗證器進行 Java Bean 驗證時，學習解決 Java 異常[`UnexpectedTypeException`](https://docs.oracle.com/javaee/7/api/javax/validation/UnexpectedTypeException.html)。 ## 1）問題當您嘗試在任何 bean 屬性上使用**錯誤的 Hiberate 驗證器注解**時，都會出現`UnexpectedTypeException`錯誤。錯誤棧跟蹤看起來像這樣。 ```java Exception in thread "main" javax.validation.UnexpectedTypeException: HV000030: No validator could be found for constraint 'javax.validation.constraints.NotBlank' validating type 'java.lang.Long'. Check configuration for 'id' at org.hibernate.validator.internal.engine.constraintvalidation.ConstraintTree.getExceptionForNullValidator(ConstraintTree.java:108) at org.hibernate.validator.internal.engine.constraintvalidation.ConstraintTree.getInitializedConstraintValidator(ConstraintTree.java:140) at org.hibernate.validator.internal.engine.constraintvalidation.SimpleConstraintTree.validateConstraints(SimpleConstraintTree.java:55) at org.hibernate.validator.internal.engine.constraintvalidation.ConstraintTree.validateConstraints(ConstraintTree.java:73) at org.hibernate.validator.internal.metadata.core.MetaConstraint.doValidateConstraint(MetaConstraint.java:127) at org.hibernate.validator.internal.metadata.core.MetaConstraint.validateConstraint(MetaConstraint.java:120) at org.hibernate.validator.internal.engine.ValidatorImpl.validateMetaConstraint(ValidatorImpl.java:533) at org.hibernate.validator.internal.engine.ValidatorImpl.validateConstraintsForSingleDefaultGroupElement(ValidatorImpl.java:496) at org.hibernate.validator.internal.engine.ValidatorImpl.validateConstraintsForDefaultGroup(ValidatorImpl.java:465) at org.hibernate.validator.internal.engine.ValidatorImpl.validateConstraintsForCurrentGroup(ValidatorImpl.java:430) at org.hibernate.validator.internal.engine.ValidatorImpl.validateInContext(ValidatorImpl.java:380) at org.hibernate.validator.internal.engine.ValidatorImpl.validate(ValidatorImpl.java:169) at com.howtodoinjava.example.TestHibernateValidator.main(TestHibernateValidator.java:25) ``` 例如，您收到上述錯誤，您嘗試將`@NotBlank`注解放在任何非字符串類型的字段中，例如`java.lang.Long`類型。 ```java public class User { @NotBlank //Incorrect usage private Long id; //More fields } ``` > 閱讀更多：[Hiberate 驗證器](https://howtodoinjava.com/hibernate/hibernate-validator-java-bean-validation/) ## 2）解決方案如問題所述，要解決此錯誤，您必須使用正確的注解。在上述問題中，`@NotBlank`注解只能應用于任何`String`字段。要驗證`long`類型字段，請使用注解`@NotNull`。 ```java public class User { public class User { @NotNull(message = "Please enter id") private Long id; @Size(max = 20, min = 3, message = "{user.name.invalid}") @NotEmpty(message = "Please enter name") private String name; //More fields } ``` 將我的問題放在評論部分。學習愉快！