Use the CDI API framework in the Java library to implement programming -oriented programming

Use the CDI API framework to realize programming Facial -oriented programming (AOP) is a programming pattern that can be separated from the core business logic that can be separated from the core business logic in the application.In the Java library, we can use the CDI API framework to achieve AOP. CDI is a dependent injection framework introduced in the Java EE 6 specification, which allows developers to easily manage the dependent relationship between components.At the same time, CDI also provides some powerful AOP functions, which can be programmed by interceptors and decorators. First, we need to create a custom interceptor class.The interceptor is used to intercept the method call, and perform some specific operations before and after the method calls.The following is a simple example: import javax.interceptor.AroundInvoke; import javax.interceptor.Interceptor; import javax.interceptor.InvocationContext; @Interceptor public class LoggingInterceptor { @AroundInvoke public Object logMethodInvocation(InvocationContext context) throws Exception { System.out.println ("Before calling ..."); // Execute the original method Object result = context.proceed(); System.out.println ("After calling ..."); return result; } } In the above examples, we use the `@Tterceptor` annotation provided by CDI to mark this class as interceptor.`@Aroundinvoke` Note indicates that the method will be executed before and after the method calls.Methods The internal logic is determined according to needs. Next, we need to add the commentary of the interceptor to the class or method of AOP.For example, we have a class named `UserService`, and there is a` GetUser` method that needs to be recorded before and after calling.The following is an example code: import javax.inject.Inject; import javax.interceptor.Interceptors; public class UserService { @Inject Logger logger; @Interceptors(LoggingInterceptor.class) public User getUser(int id) { logger.log ("Get user ..."); // Query the database to get user information return user; } } In the above examples, we use CDI's `@inject` annotations to inject a log recorder.By adding `@INTERCEPRS (LoggingInterCeptor.class)` GetUser` method, we applied to this method that we applied the `LoggingInterceptor` interceptor. In this way, when calling the `GetUser` method, the` loggingInterceptor` interceptor's `LogMethodinVocation` method will be executed separately before and after the method call. It should be noted that in order to make the interceptor take effect, we also need to enable the CDI function in the application configuration file (such as `Beans.xml`).The specific configuration method can be determined according to the application server or framework used. Through the CDI API framework, we can easily realize face -oriented programming, decoupling the horizontal sectaries from the core business logic, and improve the maintenance and reuse of the code.