The relationship between the reflection tool framework and dynamic proxy technology in the Java class library
The reflection tool framework and dynamic proxy technology are important features in the Java class library. They provide strong abilities to analyze and modify the Java class during runtime.Although both can be used to implement the dynamic calls of the objects, there are some obvious differences between them.
The reflection tool framework is a set of APIs provided by Java to obtain class information at runtime and access and modify its members (fields, methods, structure functions, etc.) without understanding its actual implementation.By using reflexes, we can dynamically create class objects, call class methods, obtain and modify field fields, etc.It provides a lot of convenience for building flexible and dynamic applications.
Here are a simple example of using reflection call method:
public class Person {
private String name;
public Person(String name) {
this.name = name;
}
public void sayHello() {
System.out.println("Hello, my name is " + name);
}
}
public class Main {
public static void main(String[] args) throws Exception {
Class<Person> personClass = Person.class;
Person person = personClass.getDeclaredConstructor(String.class).newInstance("Alice");
Method sayHelloMethod = personClass.getMethod("sayHello");
sayHelloMethod.invoke(person);
}
}
In the above code, we obtained the Class of the Person class by reflected, and used the object to create an instance of Person.We then obtained an instance of the Sayhello method using the GetMethod method and called the method through the Invoke method.
Dynamic proxy technology is another technique that is closely related to reflection. It allows to create an interface instance of the interface during runtime and provide a method of cutting -oriented programming (AOP).By using dynamic proxy, we can use additional processing without modifying the original code, such as log records and transaction management.
The following is a simple example of using dynamic proxy technology:
public interface Calculator {
int add(int a, int b);
}
public class CalculatorImpl implements Calculator {
public int add(int a, int b) {
return a + b;
}
}
public class LoggingHandler implements InvocationHandler {
private final Object target;
public LoggingHandler(Object target) {
this.target = target;
}
public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
System.out.println("Entering method: " + method.getName());
Object result = method.invoke(target, args);
System.out.println("Exiting method: " + method.getName());
return result;
}
}
public class Main {
public static void main(String[] args) {
Calculator calculator = new CalculatorImpl();
Calculator proxy = (Calculator) Proxy.newProxyInstance(
Calculator.class.getClassLoader(),
new Class[]{Calculator.class},
new LoggingHandler(calculator)
);
int result = proxy.add(2, 3);
System.out.println("Result: " + result);
}
}
In the above code, we define a Calculator interface and its implementation class Calculatorimpl.Then, we created a Logginghandler class that implemented the InvoCATIONHANDLER interface to add log records before and after the method call.Finally, we used Proxy.NewProxyinstance Methods to create an agent instance and pass the Calculatorimpl instance and Logginghandler instance.By calling the ADD method of the proxy instance, the Invoke method of Logginghandler is called, thereby realizing the logical function.
The reflection tool framework and dynamic proxy technology are powerful functions in the Java class library, and they have different applications in different scenarios.The reflection tool framework is mainly used to analyze and modify the behavior of the class, while dynamic proxy technology is used to create proxy instances for the interface during runtime, thereby realizing the intercepting and enhancement of the method call.When you need to adjust the behavior of the object according to the needs, the reflection tool framework and dynamic agency technology provide good support.
