Analysis of the technical principles of the "Iron can adjust behavior 'in the Java class library
Iron adjustment behavior (adjustability) is a powerful framework technology in the Java class library, which enables software developers to dynamically modify the behavior and functions of the program according to demand.This framework mainly depends on the reflection and dynamic agency mechanism in the Java language.
The principle of adjustability can be analyzed from the following aspects:
1. Reflective mechanism: The reflection mechanism of Java enables the program to obtain and operate various information that can obtain and operate class, including member variables, methods and constructors of class.Through reflection, we can create instances, call class methods, obtain and modify attributes, etc. at runtime.The adjustable framework can use the reflex mechanism to obtain and modify the relevant information of the class to dynamically modify the behavior of the program during runtime.
2. Dynamic proxy mechanism: Java's dynamic agency mechanism allows us to dynamically generate proxy classes for one or more interfaces when runtime. The proxy class can add additional logic before and after the call method.Through dynamic proxy, the adjustable framework can generate an agent instance for the class when runtime, so as to insert specific behavior before and after the method calls.This mechanism is widely used in AOP (facing surface programming).
The following is a simple example, demonstrating how to use the adjustable framework to realize the behavior of dynamically modifying the program during runtime:
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
interface Calculator {
int add(int a, int b);
}
class CalculatorImpl implements Calculator {
public int add(int a, int b) {
return a + b;
}
}
class LoggingHandler implements InvocationHandler {
private Object target;
public LoggingHandler(Object target) {
this.target = target;
}
public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
System.out.println("Calling method: " + method.getName());
Object result = method.invoke(target, args);
System.out.println("Method returned: " + result);
return result;
}
}
public class AdjustableBehaviorExample {
public static void main(String[] args) {
Calculator Calcultor = New Calculatorimpl (); // Create an instance
Loggingler handler = new logginghandler (Calculator); // Create a processor
Calculator proxy = (Calculator) Proxy.newProxyInstance(
Calculator.class.getClassLoader(),
new Class<?>[] { Calculator.class },
handler); // Create an agent instance
Proxy.add (2, 3); // Calling method, output log
}
}
In the above example, we first define an interface `Calculator` and its specific implementation class` Calculatorimpl`.Then, we created a `Logginghandler` class as a dynamic proxy processor, which printed the corresponding logs before and after the call method.Finally, we use the `Proxy.newproxyinstance` method to create an agency instance for` Calculatorimpl`, and then introduce `logginghandler` as a processor.When we call the ADD` method of the proxy object, it is actually called the `Invoke` method in the` logginghandler`.In the `Invoke` method, we first print the name of the method, then use the corresponding method of calling the original object with the reflex, and the result of the final return method.
Through the above examples, we can see that the adjustable framework allows us to dynamically modify the behavior of the program according to the needs and do not need to modify the source code.This technology can greatly improve the flexibility and maintenance of software, making the system more easier to expand and improve.
