The technical principle analysis and instance of the "Phantom" framework in the Java library
SHADOWING is a common framework in the Java class library. By forwarding the access request of the original object to the proxy object, the modification and control of the object behavior are realized.This article will analyze the technical principles of the Phantom Framework and provide relevant Java code examples.
1. Technical analysis
The core principle of the phantom frame is the agency mode.In the proxy mode, a public interface is defined, and the original object and the agent object implement the interface.When the client calls the method of the original object, the proxy object will intercept the request and processes related before and after execution.
1. Create a public interface
First of all, a public interface needs to be defined, and the interface defines the method that the original object and the agent object are common.For example:
public interface Image {
void display();
}
2. Create the original object
Next, realize the original object class, this class realizes public interfaces and defines specific behaviors.For example:
public class RealImage implements Image {
private String filename;
public RealImage(String filename){
this.filename = filename;
loadFromDisk();
}
private void loadFromDisk(){
System.out.println ("Load the picture from the disk:" + FILENAME);
}
@Override
public void display() {
System.out.println ("Show image:" + FILENAME);
}
}
3. Create proxy objects
Then, create a proxy object class, which also implements a public interface and contains a reference to a original object.Acting objects can add additional logic before and after the execution method.For example:
public class ProxyImage implements Image {
private RealImage realImage;
private String filename;
public ProxyImage(String filename){
this.filename = filename;
}
@Override
public void display() {
if(realImage == null){
realImage = new RealImage(filename);
}
preProcess();
realImage.display();
postProcess();
}
private void preProcess(){
System.out.println ("Pre -processing picture:" + FILENAME);
}
private void postProcess(){
System.out.println ("post -processing picture:" + FILENAME);
}
}
Example demonstration
Suppose we want to load and display a picture, using the phantom framework to add additional processing logic before and after the picture display.
public class Demo {
public static void main(String[] args) {
Image proxyImage = new ProxyImage("example.jpg");
proxyImage.display();
}
}
Output results:
Pre -processing picture: Example.jpg
Load the picture from the disk: example.jpg
Display picture: Example.jpg
Post -processing picture: Example.jpg
In the above examples, a proxyimage is created using the Phantom Framework, and a series of operations of pre -processing, loading pictures, display pictures, and post -processing by calling the Display method.
Through the phantom frame, we can modify and expand the behavior of the original object without modifying the original object code.The phantom framework is widely used in actual development in the aspects of log records, permissions control, performance monitoring, etc. to achieve dynamic management of objects.
Summarize:
This article introduces the technical principles of the phantom framework in the Java library, and provides an example of the picture loading and displaying.The phantom framework adds additional logic through the proxy mode and performs additional logic before and after the method of the original object to achieve the modification and control of the object behavior.The use of the phantom frame can flexibly manage the object to improve the maintenance and scalability of the code.