Know the principles of value :: API framework technical principles in the Java class library (API Framework in Java Class Libraries)

Know the principle of technical principles of Validation :: API framework in the java class library introduce Validation :: API framework is one of the verification framework commonly used in Java. It provides a simple and scalable way to perform data verification.This article will introduce the technical principles of Validation :: API framework, and use the Java code example to illustrate its usage. principle Validation :: API framework uses an annotation drive method to perform data verification.It uses the annotation function in the Java language to define the verification rules by adding specific annotations to the field, method or parameter.When the data needs to be verified, the validation :: API framework dynamically generate verification logic based on these annotations. Validation :: API framework provides rich verification annotations based on a set of core interfaces and implementation classes, such as@notnull,@notempty,@siZe, etc.These annotations can be applied to various scenarios, such as check whether the attribute value is empty, array or whether the collection contains elements, whether the length of the string meets the requirements, etc. Example 1. Add Maven dependence First, add Maven dependencies of validation :: API framework to your Java project.In the pom.xml file, add the following dependencies: <dependency> <groupId>javax.validation</groupId> <artifactId>validation-api</artifactId> <version>2.0.1.Final</version> </dependency> 2. Create verification rules Define a Java class that contains verification rules.For example, we create a User class that contains verification rules for user names, age and mailbox: public class User { @NotBlank private String username; @Min(18) @Max(99) private int age; @Email private String email; // omit the getter and setter method } In the above example, we used the annotation @Notblank to verify whether the user name is empty,@min and @max verifying age, and@email verification email format correctly. 3. Perform data verification Use the Validator interface of Validation :: API framework to perform data verification.The following is an example of a simple verification method: import javax.validation.Validation; imporit javax.validation.Validator; import javax.validation.ValidatorFactory; public class Main { public static void main(String[] args) { // Create Validator instance ValidatorFactory validatorFactory = Validation.buildDefaultValidatorFactory(); Validator validator = validatorFactory.getValidator(); // Create User object User user = new User(); user.setUsername(""); user.setAge(16); user.setEmail("invalid.email.com"); // Perform data verification Set<ConstraintViolation<User>> violations = validator.validate(user); // Process verification results for (ConstraintViolation<User> violation : violations) { System.out.println("Validation error: " + violation.getMessage()); } } } In the above example, we first created a value instance, then created a User object, and set some invalid attribute values.Next, we use the value method of Validator to verify the User object and obtain the verification results.Finally, we handle error information by traversing the verification results. in conclusion By using Validation :: API framework, we can easily implement the data verification function.By using the annotation driver, we can directly apply the verification rules to the class, fields, methods and parameters, and dynamically generate verification logic during runtime.This method makes data verification flexible and scalable, which greatly simplifies the development process. It is hoped that this article can help understand the technical principles of Validation :: API framework, and can apply its powerful features in actual projects.