Application cases of Javax Interceptor API in the development of Java libraries
Application cases of Javax Interceptor API in the development of Java libraries
The Javax Interceptor API is part of the Java Ee platform, which provides a method of AOP (facing surface programming) that enables developers to perform some common operations before and after the method calls.In this article, we will explore the application cases of the Javax Interceptor API and explain the complete programming code and related configuration when needed.
Case background:
Suppose we are developing a Java class library that is used to handle various payment methods.We hope to record the log before and after each payment method call, and we also want to ensure the validity of the data that passes the payment method.To achieve this goal, we can use the Javax Interceptor API.
Step 1: Create a payment class
First, we need to create a class called Payment.This will include all our payment methods.
public class Payment {
public void cashPayment(double amount) {
// Pay cash logic
System.out.println ("Cash payment" + amount + "yuan."););
}
public void cardPayment(String cardNumber, double amount) {
// Pay credit card logic
System.out.println ("Credit Card Pay" + amount + "yuan, card number:" + cardNumber);
}
// Other payment methods ...
}
Step 2: Create the interceptor class
Next, we need to create a class called PaymentInterceptor, which will play the role of an interceptor.This class needs to implement the `javax.interceptor.aroundinvoke` interface, and must contain a method of annotating modification with`@aroundinvoke`.
import javax.interceptor.AroundInvoke;
import javax.interceptor.InvocationContext;
public class PaymentInterceptor {
@AroundInvoke
public Object logAndValidatePayment(InvocationContext context) throws Exception {
System.out.println ("Record logs before the payment method call."););
// Get the method parameter
Object[] parameters = context.getParameters();
// Verify the effectiveness of payment data
if (parameters.length < 1) {
Throw New Exception ("Payment data is invalid!");
}
// execute method
Object result = context.proceed();
System.out.println ("Record logs after the payment method is called.");
return result;
}
}
Step 3: Configure the interceptor
Next, we need to configure the interceptor.We can use a class to configure the interceptor chain.This class needs to implement the `javax.interceptor.interceptorBinding` interface, and must be modified with`@InternetorBinding`.
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
import javax.interceptor.InterceptorBinding;
@InterceptorBinding
@Retention(RetentionPolicy.RUNTIME)
@Target({ElementType.TYPE, ElementType.METHOD})
public @interface PaymentInterceptorBinding {
}
Step 4: Bind the interceptor to the payment method
Finally, in the payment class, we need to bind the interceptor to each payment method so that the interceptor operation can be performed before and after calling.We can use the note to bind the interceptor to the payment method.
@PaymentInterceptorBinding
public class Payment {
@PaymentInterceptorBinding
public void cashPayment(double amount) {
// Pay cash logic
System.out.println ("Cash payment" + amount + "yuan."););
}
@PaymentInterceptorBinding
public void cardPayment(String cardNumber, double amount) {
// Pay credit card logic
System.out.println ("Credit Card Pay" + amount + "yuan, card number:" + cardNumber);
}
// Other payment methods ...
}
Step 5: Test code
Now, we can write some test code to verify the function of the interceptor.
public class Main {
public static void main(String[] args) {
Payment payment = new Payment();
// cash payment
payment.cashPayment(100.0);
// pay by credit card
payment.cardPayment("1234567890", 200.0);
}
}
The output result should be:
Record logs before the payment method call.
Cash payment is 100.0 yuan.
Record the log after the payment method is called.
Record logs before the payment method call.
Credit card payment 200.0 yuan, card number: 1234567890
Record the log after the payment method is called.
Summarize:
The above case demonstrates the application of the Javax Interceptor API in the development of the Java library.By creating a interceptor and an interceptor, we can perform general operations before and after the payment method call, such as recording the validity of the log and verifying data.This method can help us add additional functions to existing libraries without modifying the original logic.
