Introduction to the Javax Interceptor API framework in the Java class library
Introduction to the Javax Interceptor API framework in the Java class library
introduction
Javax Interceptor API is part of the Java EE standard, which provides a way to realize the interceptor mode in the application.The interceptor mode allows developers to insert additional logic in method calls, such as permissions check, log records, performance monitoring, etc.By using the Javax Interceptor API framework, developers can encapsulate these additional logic in the interceptor and apply them to the place where they need to achieve the decoupled and reuse of the code.
The working principle of the interceptor
The core idea of the interceptor mode is to bind the target method with the interceptor object.When the target method is called, the interceptor will be processed before and after the execution of the method.The interceptor is divided into two types: method interceptor and class interceptor.
Method interceptor (Method Interceptors): They can be processed before and after the execution of the target method, and the parameters and return values of the target method can be accessed.The method interceptor is fine -grained and can intercept a single method.
Class Interceptors: They can process them before and after the implementation of the entire class, but the parameters and return values of the target method cannot be accessed.Class interceptors are usually used to apply certain processing logic at the entire class.
Step of Javax Interceptor framework
1. Define a class and mark the annotation of `@Internetor`.This class will be implemented as an interceptor.
2. In the interceptor class, use the method of annotation of `@aroundinvoke`.This method will include code logic that needs to be executed before and after the implementation of the target method.
3. Use the `@Internetors` annotation of the target class or method of the interceptor.The parameters of the annotation are the bytecode object or reference of the interceptor class.
4. Run the application, the interceptor will be activated and executed by the interception logic when the target method is run.
For example code
Below is a simple example. In this example, we will show how to use the Javax Interceptor framework to implement a log block, which calls the input parameters and return values of the recording method before and after the method calls.
import javax.interceptor.AroundInvoke;
import javax.interceptor.Interceptor;
import javax.interceptor.InvocationContext;
@Interceptor
public class LoggingInterceptor {
@AroundInvoke
public Object logMethod(InvocationContext context) throws Exception {
System.out.println("Entering method: " + context.getMethod().getName());
System.out.println("Input arguments: " + context.getParameters());
Object result = context.proceed();
System.out.println("Returning from method: " + context.getMethod().getName());
System.out.println("Result: " + result);
return result;
}
}
import javax.ejb.Stateless;
import javax.interceptor.Interceptors;
@Stateless
@Interceptors(LoggingInterceptor.class)
public class Calculator {
public int add(int a, int b) {
return a + b;
}
}
In the above example, we define a blocking class `LoggingInterceptor`, and use the@AroundinVoke` annotation to mark the` logmethod` method.In this method, we obtained the name, input parameter, and return value through the `InvacationContext` object, and print them to the console.
We also define a `Calcortor` class that uses the`@stateless` annotation mark, indicating that it is a stateless EJB component.By using the@Internetors` annotation on the `Calculator` class, we apply all the methods of this class.
in conclusion
The Javax Interceptor API framework provides developers with a standard way to implement the interceptor mode.By using this framework, developers can easily implement functions such as log records, permissions inspection, and performance monitoring.This flexibility and reuse make the code more modular and maintained, and is an important tool for developing high -quality Java applications.
