In-depth understanding of Validation :: API framework technical principles in the Java class library

In -depth understanding of Validation :: API framework technical principles in the Java class library Brief introduction In modern software development, data verification is a vital link that can ensure that the application receives legal and effective data.In order to simplify the development process, the Java library introduces Validation :: API framework, which provides a simple and flexible way to verify data.This article will explore the technical principles of value :: API framework, and provide some Java code examples to help readers better understand. 1. Validation :: API Framework Overview Validation :: API framework is located in the javax.validation package. It is part of the Java Ee (Enterprise Edition) specification. It can also be used as an independent framework in the Java SE (Standard Edition) environment.This framework provides a set of annotations and APIs that can be applied to the Java Bean field, method parameters, and return values to achieve data verification. 2. Core concept 2.1 constraint annotation The constraint annotation is one of the core elements of Validation :: API framework. It is used for verification constraints for marking fields, parameters, or method return values.The framework provides many default constraints, such as@notnull,@size, and @Pattern.At the same time, developers can also customize constraints to meet specific business needs. 2.2 Validator (Validator) The testor is another key concept of Validation :: API framework, which is used to perform specific verification logic.The verification device is automatically created and managed by Validation :: API framework, and developers do not need to create or manage them.The verification device can verify the legitimacy of different data types and constraints to verify the legitimacy of the data. 2.3 Constant Validator The constraint authentication is a specific implementation of the laboratory, which is used to verify specific constraint annotations.Each constraint annotation can be associated with one or more constraints.When the application uses a specific constraint annotation to verify the data, the relevant constraint authentication will be automatically called to verify. 3. Data verification process Verification data is a typical three -step process: configuration, execution and report. 3.1 Configuration Developers need to configure the verification engine, which is responsible for organizing and executing the verification process.In this step, a verification device factory needs to be constructed to create an instance of the school inspector through the factory. ValidatorFactory factory = Validation.buildDefaultValidatorFactory(); Validator validator = factory.getValidator(); 3.2 Execution Once the verification device is ready, the data method can be used to verify the data using the value method.This method accepts the Java Bean object to be verified as a parameter, and returns a set that contains all verification errors. Set<ConstraintViolation<User>> violations = validator.validate(user); 3.3 Report The last step is to process verification errors.Validation :: API framework provides a variety of ways to deal with verification errors, such as throwing abnormalities, recording logs or output to the console.The actual processing method depends on the needs of the application. 4. Example code The following is a simple Java class that demonstrates the use of value :: API framework: public class User { @Notnull (Message = "Username cannot be empty") @Size (min = 5, max = 20, message = "User name must be 5 ~ 20 characters") private String username; @Notnull (Message = "Password cannot be empty") @Size (min = 8, message = "Password length is at least 8 characters") private String password; // getters and setters } public class Main { public static void main(String[] args) { User user = new User(); user.setUsername("abc"); user.setPassword("1234567"); ValidatorFactory factory = Validation.buildDefaultValidatorFactory(); Validator validator = factory.getValidator(); Set<ConstraintViolation<User>> violations = validator.validate(user); for (ConstraintViolation<User> violation : violations) { System.out.println(violation.getMessage()); } } } The above code defines a User class and used constraint annotations on the field for verification.In the main class, first created a User object and set the field value, and then verified it by the verification device and printed the verification error information. in conclusion Validation :: API framework provides a simple, flexible and scalable data verification mechanism for Java developers.This article discusses the core concept, data verification process, and sample code of the framework. I hope that readers can understand the technical principles of Validation :: API framework through this article, and apply it in actual projects to ensure the legitimacy of the data.