Methods and principles to realize custom interceptors -Javax Interceptor API framework
Methods and principles to realize custom interceptors -Javax Interceptor API framework
Overview:
The interceptor is a common design mode that allows us to add additional logic before and after the method execution.In Java, we can use the Javax Interceptor API framework to achieve the interceptor.This article will introduce how to use this framework to create custom interceptors and explain its implementation principles.
1. Import dependencies
First, we need to add the Javax Interceptor API framework library to the dependence of the project.We can add the following dependencies in Maven or Gradle configuration files to introduce this library:
Maven project dependency configuration:
<dependency>
<groupId>javax.interceptor</groupId>
<artifactId>javax.interceptor-api</artifactId>
<version>1.2.2</version>
</dependency>
Gradle project dependency configuration:
groovy
dependencies {
implementation 'javax.interceptor:javax.interceptor-api:1.2.2'
}
2. Create an interceptor
In the Java project, we can create a blocking of javax.interceptor.invocontext interface by creating a defined interceptor.This interface defines the method that the interceptor needs to be implemented.
Below is a code of an example interceptor:
import javax.annotation.Priority;
import javax.interceptor.AroundInvoke;
import javax.interceptor.Interceptor;
import javax.interceptor.InvocationContext;
@Interceptor
@Priority(Interceptor.Priority.APPLICATION)
public class MyInterceptor {
@AroundInvoke
public Object intercept(InvocationContext context) throws Exception {
// The logic added before the method execution
System.out.println ("" Interception logic before calling ");
// Call the intercepted method
Object result = context.proceed();
// The logic added after the method execution
System.out.println ("Interception logic after calling");
return result;
}
}
In the above code example, we created a interceptor class called MyInterceptor, which uses @Interceptor annotation labeling. It is a interceptor.@Priority annotation is used to specify the priority of the interceptor.
@AnDInVoke comments are used to mark the interception method. In this method, we can add additional logic, and then call the interception method by the provocationContext method.
3. Use the interceptor
To use the interceptor, we need to add @Interceptors annotation to the intercepted method and specify the interceptor class.
The following is an example code that shows how to use the interceptor:
import javax.interceptor.Interceptors;
public class MyClass {
@Interceptors(MyInterceptor.class)
public void myMethod() {
// The implementation logic of the method
}
}
In the above code example, we applied the MyInterceptor interceptor to the MyMethod () method, and specified the interceptor class through the @Interceptors annotation.
Explanation of the principle of implementation:
The implementation principle of the Javax Interceptor API framework is based on the Java reflection mechanism.When we call the interception method, the underlying framework will call the intercept () method of the interceptor through the reflection mechanism, and additional logic can be added to this method.The framework is then called through the reflection mechanism to realize the function of the interceptor.
Summarize:
This article introduces how to use the Javax Interceptor API framework to implement the method and principles of custom interceptors.We first add the framework to the dependence of the project, and then create a interceptor class that implements the InvoCationContext interface to customize the interception logic.Finally, we can use the interceptor by adding @Interceptors annotation to the interception method.Through this framework, we can add additional logic before and after the method execution to achieve more flexible business processing.
