Detailed explanation of the technical principles of the Bean Validation Scala framework in the Java class library
Detailed explanation of the technical principles of the Bean Validation Scala framework in the Java class library
Overview:
Bean Validation is a specification of Java, which is used to verify the attribute value of Java Bean.The SCALA framework is a framework of the Java library, which contains the implementation of Bean Validation.This article will introduce Bean Validation in detail and its technical principles in the SCALA framework, and provide some Java code examples to illustrate.
1. Overview of Bean Validation:
Bean Validation is a specification of Java, which aims to provide a general verification mechanism to ensure that the attribute value of the object meets specific constraints.It can be applied to any Java object and can be configured by annotating or programming.
2. Annotation of Bean Validation:
Bean Validation uses annotations to define the constraints of attributes.Common annotations are:
-@Notnull: The attribute is not allowed to be null.
-@Size (min = x, max = y): The attribute length must be between x and y.
-@Pattern (regexp = "xxxx"): The attribute must match the specified regular expression.
These annotations can be directly applied to the attributes of Java Bean.
3. The execution process of Bean Validation:
-When the application needs to verify a Java Bean, it uses Bean Validation's verification engine.
-We engine first read the attribute annotation information of the Bean and obtain constraints.
-The engine checks whether the attribute value of the Bean meets the constraints.If it is not satisfied, the engine will generate a verification error message.
-The application can process verification error messages as needed, such as displayed to users or recorded in the log.
4. Bean Validation and SCALA framework:
SCALA is a static type programming language running on JVM and has good interoperability with Java.The SCALA framework is a framework of the Java library, so Bean Validation can be used to verify the attributes in Scala.
The following is an example showing how to use Bean Validation in the SCALA framework:
scala
import javax.validation.constraints.{NotNull, Size}
import javax.validation.Validation
import scala.beans.BeanProperty
class User {
@BeanProperty
@NotNull(message = "Name must not be null")
@Size(min = 1, max = 50, message = "Name length must be between 1 and 50")
var name: String = _
}
object Main extends App {
val user = new User()
user.setName(null)
val validator = Validation.buildDefaultValidatorFactory().getValidator()
val violations = validator.validate(user)
for (violation <- violations) {
println(violation.getMessage())
}
}
In the above example, the User class uses the @Beanproperty annotation to convert the name property into the Java Bean property.Use@beanproperty,@notnull, and @size annotations to define verification constraints on the name attribute.
In the main object, we created a User object and set its name property to NULL.Next, obtain the verification device and verify the User object.If the verification fails, it will print the verification error message.
in conclusion:
This article introduces the basic concepts and usage methods of Bean Validation, as well as the technical principles of using Bean Validation in the SCALA framework.By using Bean Validation, developers can easily verify the attribute values of Java Bean and process verification errors when needed.
