Analysis of the technical principles of Jakarta Interceptors in Java Library

Analysis of the technical principles of Jakarta Interceptors in Java Library Overview: With the rapid development of enterprise Java development, the management of Cross-Cutting Concers in application processing has become increasingly important.The Jakarta Interceptors framework provides an elegant and reusable way to handle these concerns. It is based on Java's reflection mechanism to allow developers to intercept and modify methods calls during the life cycle of the application. Technical principle: The core concept of the Jakarta Interceptors framework is the interceptor, which is a special type of class that can be called before, after or after an abnormal occurrence.The interceptor can be used for various purposes, such as log records, security certification, transaction management, etc. In the Jakarta Interceptors framework, the commentary is used to mark the interceptor.An interceptor class usually implements one or more interceptors.These annotations include: -@Aroundinvoke: The parameters and return values of the method can be modified to modify the method. -@Before: The parameters and return values that cannot be modified before the method execute before executing the method. -@AFTER: Used to intercept the call after the method executes, and the return value of the method can be modified. -@AFTERTHROWING: Used to intercept calls when the method occurs abnormal, and can handle abnormalities. When using the Jakarta Interceptors framework, we need to follow the steps below: 1. Create an interceptor class: First, we need to create a interceptor class to achieve the interceptor annotation interface.In the interception method, we can add code according to the needs to achieve the required logic. For example, we create a interceptor called LoggingInterceptor to implement the @AaroundinVoke annotation interface.In the interception method, we can print log information before and after the method execution. import javax.interceptor.AroundInvoke; import javax.interceptor.InvocationContext; public class LoggingInterceptor { @AroundInvoke public Object logMethod(InvocationContext context) throws Exception { System.out.println("Entering method: " + context.getMethod().getName()); Object result = context.proceed (); // call the intercepted method System.out.println("Exiting method: " + context.getMethod().getName()); return result; } } 2. Apply a interceptor in the target class: Next, we need to apply a interceptor on the target method.To this end, we can use annotations provided by the Jakarta Interceptors framework. For example, we have a class called UserService, which contains a method called Saveuser.We can apply LoggingInterceptor interceptors to intercept the calls of the SaveUser method. import javax.interceptor.Interceptors; @Interceptors(LoggingInterceptor.class) public class UserService { public void saveUser(User user) { // Save user logic } } 3. Configuration interceptor: Finally, we need to configure the interceptor in the configuration file of the application.The specific configuration method depends on the container or framework used. For example, in Java Ee, we can configure the interceptor in the Beans.xml file. <beans xmlns="http://xmlns.jcp.org/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/beans_2_0.xsd" bean-discovery-mode="all"> <interceptors> <class>com.example.LoggingInterceptor</class> </interceptors> </beans> In this way, when the Saveuser method of the UserService class is called, the loggingInterceptor interceptor will printed log information before and after the method execution. in conclusion: Through the Jakarta Interceptors framework, developers can be more flexible and reused land to process horizontal sectaries in applications.It allows us to intercept and modify method calls at critical moments such as before and after the method execution.This mechanism can greatly simplify the writing and maintenance of code, and improve the readability and maintenance of applications. I hope this article can help readers better understand and apply the Jakarta Interceptors framework.By using this technology, we can better manage and process cross -sectional attention in the application to improve the flexibility and scalability of the system. Example of additional code: In this example, we use the Jakarta Interceptors framework to write a simple log record interceptor to demonstrate the use of the framework. import jakarta.interceptor.AroundInvoke; import jakarta.interceptor.InvocationContext; public class LoggingInterceptor { @AroundInvoke public Object logMethod(InvocationContext context) throws Exception { System.out.println("Entering method: " + context.getMethod().getName()); Object result = context.proceed (); // call the intercepted method System.out.println("Exiting method: " + context.getMethod().getName()); return result; } } import jakarta.interceptor.Interceptors; @Interceptors(LoggingInterceptor.class) public class UserService { public void saveUser(User user) { // Save user logic } } <beans xmlns="http://xmlns.jcp.org/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/beans_2_0.xsd" bean-discovery-mode="all"> <interceptors> <class>com.example.LoggingInterceptor</class> </interceptors> </beans>