The technical principles of the Java class library Validation :: API framework (in-depth explanation of the technical principles of value :: API Framework in Java Class Libraares)
Detailed explanation of the technical principles of Java Library Validation :: API framework
Java Class Library Validation :: API (hereinafter referred to as Validation API) is an open source framework for data verification. It provides a set of powerful tools and specifications to verify data in the Java program.This article will explore the technical principles of the Validation API framework and provide some Java code examples to help readers better understand.
1. Validation API Overview
Validation API is the standardized data verification framework of Java, which aims to help developers perform data verification and inspection easily.It allows developers to verify the data by using annotations or programming, and provide a set of standard verification annotations (such as@notnull,@max,@min, etc.) for developers.
2. Core module
The core module of Validation API includes the following key components:
-Constraint: constraint is one of the important concepts in the Validation API.It represents the verification requirements of data.For example,@notnull annotations indicate that the corresponding fields or parameters cannot be empty.
-VALIDATOR: Verification is an object used to verify data.It is an implementation of the ConstraintValidator interface and is used to determine specific verification logic.The verification device can be applied to different fields or parameters, and verification is verified based on the corresponding constraints.
-CONSTRAINTVIOLATION: Constraining violations refers to the situation where the data found during the verification process does not meet the constraint requirements.The verification process will generate the Constraintvilation object, which contains useful information about violations, such as illegal fields, illegal values, and messages of constraints.
3. Introduce Validation API
To use the Validation API in the Java project, we first need to introduce the corresponding dependence.It can be implemented by adding the following dependency items to the pom.xml file of the project::
<dependency>
<groupId> jakarta.validation </groupId>
<artifactId> jakarta.validation-api </artifactId>
<version>2.0.2</version>
</dependency>
4. Use annotations to verify
Validation API supports the use of annotations to verify data.Developers can add corresponding verification annotations to fields, method parameters or return values.Here are some commonly used verification annotations:
-@Notnull: Make sure that fields or parameters are not empty.
-@Size: Make sure the size of the field or parameters is within the specified range.
-@Pattern: Make sure the field or parameters match the specified regular expression.
The following is an example of verification using annotations:
public class User {
@NotNull
private String name;
@Size(min = 8, max = 16)
private String password;
// getters and setters
}
5. Programming method verification
In addition to using annotations for verification, the Validation API also supports verification by programming.Developers can make manual verification by creating the Validator object and calling their value () methods.The following is an example of verification by programming method:
ValidatorFactory factory = Validation.buildDefaultValidatorFactory();
Validator validator = factory.getValidator();
User user = new User();
Set<ConstraintViolation<User>> violations = validator.validate(user);
for (ConstraintViolation<User> violation : violations) {
System.out.println(violation.getMessage());
}
6. Customized constraint
Validation API also allows developers to create customized constraints and verifications to meet specific application needs.For this reason, only a verification device that implements the ConstraintValidator interface, and uses the corresponding field or parameters of the custom annotation mark.The following is an example of custom constraints:
@Target({ ElementType.FIELD })
@Retention(RetentionPolicy.RUNTIME)
@Constraint(validatedBy = CustomValidator.class)
public @interface CustomConstraint {
String message() default "Custom constraint violation";
Class<?>[] groups() default {};
Class<? extends Payload>[] payload() default {};
}
public class CustomValidator implements ConstraintValidator<CustomConstraint, String> {
@Override
public boolean isValid(String value, ConstraintValidatorContext context) {
// Customized verification logic
return false;
}
}
public class User {
@CustomConstraint
private String customField;
// getters and setters
}
By using custom constraint annotations and verifications, developers can perform higher -level data verification based on specific business rules.
Summarize:
This article conducts a detailed explanation of the technical principles of the Java class library value :: API framework, and provides examples of verifying the use of annotations and programming methods.Validation API provides developers with a simple and powerful way to verify data in the Java program.By using the Validation API reasonably, developers can improve the integrity and reliability of data to ensure the correctness of the application.
