How to use forced inheritance to proxy final classes in Java to achieve better code organization and management?

How to use forced inheritance to proxy final classes in Java to achieve better code organization and management?

In Java, a final class refers to a class that cannot be inherited. Normally, we declare a class as final to ensure the stability and safety of its behavior. However, sometimes we want to be able to perform some additional operations when using final classes, such as adding logging, permission verification, etc. At this time, we can use the feature of forced inheritance of the proxy final class to achieve better code organization and management.

The proxy pattern is a commonly used design pattern that can add some additional functionality without changing the original class. In Java, the principle of using forced inheritance to proxy a final class is to create a new class, inherit the final class and extend its functionality. Let's illustrate this process through an example:

Suppose we have a final class FinalClass, which defines some core business logic, as shown below:

public final class FinalClass {
    public void doSomething() {
        System.out.println("Doing something important...");
    }
}

Now, we need to use FinalClass Add logging function. We can define a proxy class ProxyFinalClass, inherit FinalClass, and add logging in the doSomething method, as shown below:

public class ProxyFinalClass extends FinalClass {
    private FinalClass finalClass;
    
    public ProxyFinalClass(FinalClass finalClass) {
        this.finalClass = finalClass;
    }
    
    @Override
    public void doSomething() {
        System.out.println("Before doSomething...");
        
        finalClass.doSomething();
        
        System.out.println("After doSomething...");
    }
}

In the above code, we pass the instance of FinalClass into the proxy class ProxyFinalClass through the constructor method , and call the original method of FinalClass in the overridden doSomething method, and add some extra operations before and after the call.

The following is a usage example:

public class Main {
    public static void main(String[] args) {
        FinalClass finalClass = new FinalClass();
        ProxyFinalClass proxyFinalClass = new ProxyFinalClass(finalClass);
        
        proxyFinalClass.doSomething();
    }
}

Run the above sample code, the output is as follows:

Before doSomething...
Doing something important...
After doSomething...

Through the above example, we can see that through forced inheritance, the proxy final class In this way, we successfully added the logging function to FinalClass without affecting the original stability and security of FinalClass.

By using forced inheritance to proxy final classes, we can achieve better code organization and management. We can define multiple different proxy classes and add specific functions to each proxy class to achieve flexible extension of the final class. At the same time, this approach can also help us better follow the opening and closing principle, that is, open to extensions and closed to modifications.

Summary:

This article introduces how to use forced inheritance of proxy final classes in Java to achieve better code organization and management. By defining a proxy class and extending the functions of the final class in it, we can achieve flexible use of the final class. This approach can not only increase the functionality of the class, but also help us better follow design principles and improve code quality.

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