The comparative study of Java reflection library and dynamic agent
The comparative study of Java reflection library and dynamic agent
1 Introduction
Java is an object -oriented programming language, which provides two powerful characteristics of reflection and dynamic proxy.This article will compare the Java reflection library and dynamic agent to discuss their advantages and disadvantages and applicable scenarios.
2. reflection
Reflection refers to the ability to dynamically obtain and operate, methods, fields, etc. at runtime.Java's reflection mechanism allows programs to obtain specific information of the class during runtime, and can call the class method, create objects, etc. at runtime.Reflex provides a flexible way to operate and extend the code, but it will also introduce some performance loss.
The following is an example of using reflexes to create objects and call methods:
Class<?> clazz = Class.forName("com.example.MyClass");
Constructor<?> constructor = clazz.getConstructor();
Object obj = constructor.newInstance();
Method method = clazz.getMethod("doSomething");
method.invoke(obj);
3. Dynamic proxy
Dynamic proxy refers to the dynamic creation of a proxy object during runtime to call the method instead of real objects.Java's dynamic proxy mechanism allows procedures to create proxy objects by implementing interfaces or inheritance classes, and insert custom logic before and after the method of proxy object calls.Dynamic proxy is usually used to implement some advanced functions such as AOP (facing cut -out programming).
The following is an example of using a dynamic proxy call method and inserting custom logic:
interface MyInterface {
void doSomething();
}
class RealObject implements MyInterface {
public void doSomething() {
System.out.println("Doing something...");
}
}
class MyInvocationHandler implements InvocationHandler {
private Object target;
public MyInvocationHandler(Object target) {
this.target = target;
}
public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
System.out.println("Before method call");
Object result = method.invoke(target, args);
System.out.println("After method call");
return result;
}
}
public class Main {
public static void main(String[] args) {
RealObject realObject = new RealObject();
MyInvocationHandler handler = new MyInvocationHandler(realObject);
MyInterface proxy = (MyInterface) Proxy.newProxyInstance(
realObject.getClass().getClassLoader(),
realObject.getClass().getInterfaces(),
handler
);
proxy.doSomething();
}
}
4. Comparison
There are some similarities in reflection and dynamic proxy, but there are also obvious differences.
-The reflection can operate any class or objects, and dynamic proxy can only operate the interface or implement the class of interfaces.
-The reflection can obtain and operate all information, including private members and methods, and dynamic proxy can only access the interface or implement public methods in the class.
-The reflection can create flexible operations such as objects and call methods, but the performance is poor.The performance of dynamic proxy is relatively good because it has less logic inserted before and after calling the real method.
-The reflection is more suitable for dynamic operations and objects according to the conditions during runtime.Dynamic proxy is more suitable for inserting universal logic before and after the call method, to realize the functions of transaction management and performance monitoring.
5. Applicable scenarios
Reflex and dynamic proxy are the strong features of Java. They can increase the flexibility and scalability of the code without modifying the source code.Reasonable choice of reflection or dynamic proxy depends on specific needs.
-If you need to operate all members and methods of the class, including privately, you can choose to use reflection.
-If you only need to operate the method of the interface or interface implementation class, and you want to insert the custom logic before and after the method call, you can choose to use a dynamic proxy.
-If you need to create and operate objects dynamically at runtime, and tolerate some performance loss, you can choose to use reflection.
-If you need to insert universal logic before and after the method call, and high requirements for performance, you can choose to use dynamic proxy.
Summary: The Java reflection library and dynamic agent are two powerful features, and have their own application advantages in different scenarios.The correct selection and reasonable use of these two characteristics can make Java development more flexible and scalable.
