Research on the technical principles of JAKARTA Interceptors in Java Library
Jakarta Interceptors is a framework technology used to realize the interceptor mode in the Java class library.The interceptor mode is a commonly used design mode that adds additional functions to the code without modifying the original code.This article will study the principles of Jakarta Interceptors and how to use the framework technology in the Java project.
## interceptor mode
In software development, the interceptor mode allows developers to inject customized code into before and after performing certain key operations, thereby achieving intercepting and enhancement of method calls.It provides a scalable way to change the behavior without changing the source code directly.The interceptor mode is very useful in some common tasks, such as log records, performance monitoring, error handling, etc.
## jakarta interceptors
Jakarta Interceptors is part of the JAKARTA EE (formerly known as the Java EE) specification and aims to provide a lightweight, annotated interceptor implementation for Java developers.It provides a simple way to define and apply interceptors, as well as performing corresponding interception logic before and after the method calls.
### interceptor annotation
Jakarta Interceptors use @Interceptor annotation as a mark to indicate that a class is a interceptor.One interceptor class must meet the following conditions:
-De @interceptor annotation must be used for labeling.
-News must be implemented by one or more marked as @InterceptorBinding.
### interceptorBinding annotation
The interceptorBinding annotation is a custom annotation to indicate what methods or classes will be applied to the interceptor.When using Jakarta Interceptors, developers need to define their interceptorBinding annotations and mark them on the interceptor class.
@Target({ElementType.TYPE, ElementType.METHOD})
@Retention(RetentionPolicy.RUNTIME)
@InterceptorBinding
public @interface MyInterceptorBinding {
}
In the above example, we define an interceptorBinding annotation called MyInterceptorBinding.
### interceptor class
The interceptor class is the core component to realize the logic.By implementing a interceptor interface, developers can add customized processing logic before and after the method call.
@Interceptor
@MyInterceptorBinding
public class MyInterceptor implements Serializable {
@AroundInvoke
public Object intercept(InvocationContext ctx) throws Exception {
// Preface to interception logic
System.out.println("Intercepted before method execution");
// Call the original method
Object result = ctx.proceed();
// Rear interception logic
System.out.println("Intercepted after method execution");
return result;
}
}
In the above examples, we use the @Interceptor annotation to mark the MyInterCepptor class, and use the @MyinterCepptorBinding annotation to indicate that the interceptor will be applied to the method or class that marked @MyinterCepptorBinding.By using the @AaroundinVoke annotation on the Internet method, we define the processing logic of the interceptor.
### Application interceptor
To apply a interceptor in the Java class library, developers need to use the interception annotation to mark the classes or methods that need to be intercepted.
@MyInterceptorBinding
public class MyClass {
@MyInterceptorBinding
public void myMethod() {
// Method logic
}
}
In the above example, we used the @MyinterceptorBinding annotation on the MyClass class, indicating that the class will be used to intercept.Similarly, we also used the @MyinterceptorBinding annotation on the MyMethod method, indicating that the method will apply the interceptor.
### interceptor chain
When the intercepting method is called in the application, the interceptor chain will execute the corresponding interceptor in a certain order.
In the above schematic diagram, the order of the interceptor chain is executed from top to bottom.Each interceptor can execute your own logic before and after the method call.
### abnormal processing
Jakarta Interceptors also supports the abnormalities thrown in the processing method call.Developers can add corresponding abnormal processing logic by capturing abnormalities and using @Aroundinvoke and @AroundConstruct annotations.
@AroundInvoke
public Object intercept(InvocationContext ctx) throws Exception {
try {
return ctx.proceed();
} catch (SomeException e) {
// Abnormal processing logic
}
}
In the above examples, we can process the abnormalities in the processing method by capturing the SomeException exception and adding the corresponding processing logic.
## Summarize
This article discusses the principle of the Jakarta Interceptors framework and the method of using the framework technology in the Java library.By using Jakarta Interceptors, developers can easily implement the interceptor mode and add custom functions before and after the method call.
