The technical principles and practice of the Bean Validation Scala framework in the Java class library
The technical principles and practice of the Bean Validation Scala framework in the Java class library
introduction:
When developing applications, data verification is a very important task that ensures that the input data meets the expected format and specifications.In order to simplify the process of data verification and reduce repeated code writing, the Java class library provides the Bean Validation framework.In SCALA application development, we can also use the framework to achieve convenient and efficient data verification.This article will introduce the technical principles and practices of Bean Validation in SCALA, while providing some related Java code examples.
Introduction to Bean Validation:
Bean Validation is part of the Java EE specification. It defines a set of APIs and constraints for verifying the JavaBean object.These annotations can be returned on the attributes, method parameters and method of applying to JavaBean.The Bean Validation framework provides a unified verification mechanism that can be used to check the data in the object or object diagram, and verify it through the specified constraints.These constraints can be predetermined or customized, and can be implemented by writing the corresponding verification device.This framework also provides a series of error report mechanisms that facilitate developers to quickly locate and solve data verification problems, thereby improving the robustness and reliability of applications.
2. Bean Validation constraint annotation and verification device:
The Bean Validation framework defines some commonly used constraint annotations, such as@notnull,@notblank,@size,@min,@max, etc.These annotations can be used directly on the attributes of JavaBean to specify the constraints of the attribute.For example,@notnull annotation is used to check whether the attribute value is null,@notblank annotation is used to check whether the attribute value is an empty string.For attribute values that are not met with constraints, the framework will throw the corresponding abnormal information.
In addition to using existing constraints, developers can also customize constraint annotations and verifications.Customized constraints need to be marked with @Constraint annotations and specify the corresponding verification device.The verification device is a class that implements the ConstraintValidator interface and covers the ISVALID method.The ISVALID method is used to define the verification logic of custom constraints.In this way, developers can define and apply various custom data verification rules according to specific business needs.
The following is an example of using custom constraint annotations and verifications:
@Target({ ElementType.FIELD, ElementType.PARAMETER })
@Retention(RetentionPolicy.RUNTIME)
@Constraint(validatedBy = CustomValidator.class)
public @interface CustomConstraint {
String message() default "Invalid value";
Class<?>[] groups() default {};
Class<? extends Payload>[] payload() default {};
}
public class CustomValidator implements ConstraintValidator<CustomConstraint, String> {
@Override
public void initialize(CustomConstraint constraintAnnotation) {
}
@Override
public boolean isValid(String value, ConstraintValidatorContext context) {
// Customized verification logic
return value != null && value.startsWith("ABC");
}
}
public class User {
@CustomConstraint
private String username;
// omit Getter and Setter
}
In the above examples, we define a custom constraint notes, and specify the corresponding verification device CustomValidator.The verification device is used to verify the value of the username property.In verification logic, we verify whether the strings start with "ABC" to check.If the attribute value meets the verification rules, the verification device returns true; otherwise, return false.
Third, use Bean Validation in SCALA:
The Bean Validation framework is completely compatible with Scala, so we can use the framework directly in the SCALA code.First, we need to add Bean Validation related dependence to the project.For the Scala Play framework, the following dependencies can be added to the Build.sbt file:
scala
libraryDependencies += "org.hibernate.validator" % "hibernate-validator" % "6.2.0.Final"
After adding dependencies, you can use the Bean Validation framework in the Scala code.The following is an example of data verification using Bean Validation:
scala
import javax.validation.constraints.{NotBlank, Size}
import scala.util.control.Exception._
case class User(
@(NotBlank @field)
@(Size(min = 6, max = 20) @field)
username: String,
@(NotBlank @field)
@(Size(min = 8) @field)
password: String
)
val user = User("", "abc123")
val validationResult = catching(classOf[ConstraintViolationException]).either {
val validatorFactory = Validation.buildDefaultValidatorFactory()
val validator = validatorFactory.getValidator()
validator.validate(user)
}
validationResult match {
case Left(exception) =>
val errorMessages = exception.getConstraintViolations.map(_.getMessage)
println(s"Validation failed: ${errorMessages.mkString(", ")}")
case Right(_) =>
println("Validation passed")
}
In the above example, we define a case class named User, using the restraint annotation annotation of the Bean Validation framework on the attributes.By calling the value.Validate (user) method, you can check the User type object.The verification results return a ConstraintviolationException exception, which contains detailed information about the failure of the verification.We can further extract the error messages by obtaining the Constraintvilation object in the exception.
in conclusion:
This article introduces the technical principles and practice of Bean Validation in SCALA.Through the Bean Validation framework, we can easily check the data and meet specific business needs by custom constraint annotations and verifications.By applying Bean Validation reasonably, it can improve the reliability and robustness of the application.At the same time, we also provide relevant Java code examples to help readers better understand and apply the framework.
Reference materials:
-Bean value official website: https://beanvalidation.org/
-Hibernate value document: https://docs.jboss.org/hibernate/stable/validator/reference/en-s/html_single/
