Analyze the technical principles of the verification framework framework in the Java library

Title: Analysis of the technical principle of verification framework in the Java class library In the development of Java, the legitimacy of verifying the input data is a very important step. To simplify this process, the Java class library often uses the verification framework to automate the verification process.This article will analyze the technical principles of the verification framework in the class library of Java, including verification processes, annotations and implementation methods. 1. The basic principle of verification framework The basic principle of the verification framework is to embed the verification rules in the Java class, and then analyze and execute these rules through the framework at runtime to verify the legitimacy of the input data. 2. Verification process Before using the verification framework, the verification rules are first defined, that is, the annotation.Common authentication annotations include@notnull,@size,@min,@max, etc.Then use these annotations to mark the fields in the classes required. When the input data is required, the verification framework will obtain a class to be verified through the reflection mechanism and traverse the fields in the class.For fields marked, the verification framework will read the corresponding annotation information, and verify the verification rules defined in the annotation.If the verification fails, the corresponding abnormality or error message will be thrown. Third, annotation mechanism The annotation is the core of the verification framework. It realizes the automation of verification by associating the verification rules with the fields of the Java class.A series of predefined annotations are usually provided in the verification framework, and developers can also customize annotations to achieve more verification rules. When achieving custom annotations, generally need to use meta annotations @Target and @Retention to specify the target and life cycle of the annotation.Common targets include FIELD (field), Method (method), and class (class), and the life cycle includes Source (source code), class (compiled) and Runtime. Fourth, the implementation of the verification method The implementation method of the verification framework can be divided into two types: reflection and agency -based. 1. Reflex -based verification method: Based on reflection -based verification methods is a common implementation method of verification framework. It reads all fields in the class through the reflection mechanism and performs corresponding verification rules according to the annotations on the field.Code example: public class User { @NotNull @Size(min = 1, max = 10) private String username; // omit other fields and methods } public class Validator { public static void validate(Object obj) throws ValidationException { // Obtain the class object of the object Class<?> clazz = obj.getClass(); // Traversing all fields for (Field field : clazz.getDeclaredFields()) { // Judging whether there are annotations on the field if (field.isAnnotationPresent(NotNull.class)) { // Perform the corresponding verification rules // ... } // Judate whether there are other annotations on the field and perform corresponding verification rules // ... } } } // Call the verification method User user = new User(); Validator.validate(user); 2. A proxy verification method: The proxy -based verification method is to generate an agent object during runtime and perform the verification logic in the proxy object.Code example: public interface Validator { void validate(Object obj) throws ValidationException; } public class RealValidator implements Validator { public void validate(Object obj) throws ValidationException { // Execute verification logic // ... } } public class ValidatorProxy implements Validator { private Validator validator; public ValidatorProxy(Validator validator) { this.validator = validator; } public void validate(Object obj) throws ValidationException { // Execute the front processing logic // ... // Call the real verification object validator.validate(obj); // Execute the post -processing logic // ... } } // Call the verification method User user = new User(); Validator validator = new ValidatorProxy(new RealValidator()); validator.validate(user); Through the above two implementation methods, the verification framework can realize the legality of automatic verification input data, reduce repeated verification code, and improve development efficiency. Summarize: The verification framework in the Java class library realizes automated verification of the legality of input data through the implementation of the annotation mechanism and verification method.Developers can quickly realize the data verification function by defining the verification rules and implementing verification methods.The design idea of this verification framework can improve the maintenance and scalability of the code, and reduce the workload of manual writing verification code.