# Purpose

The Proxy pattern provides a substitute for an object to control access, postpone its creation or perform additional actions (lazy loading, validation, etc.).

We can see it as a representative that acts as an intermediary with the real object.

# Problem

• Access Control: Restrict who accesses the object.

• Creation Costs: Postpone creation of heavy objects (lazy loading).

• Remote References: Work with objects in other memory spaces.

# Solution

The solution proposed by Proxy is:

• Substitution: Intermediary with an identical interface to the real object.

• Control: Adds validation, lazy loading or security before delegating.

# Structure

# Participants

• Subject: Common interface for Proxy and RealSubject.
• RealSubject: The object that performs the real operation.
• Proxy: Representative that controls access.
• Client: Uses the intermediary.

# When to Use It

• Need for strict access control.

• Management of expensive operations on demand.

# Example: HD Images

We manage high resolution images. They are heavy and loading them all at startup is not efficient.

# Java Code

class ImageProxy implements Image {
    private HighResImage realImage;
    public void display() {
        if (realImage == null) realImage = new HighResImage(path);
        realImage.display();
    }
}

public class Client {
    public static void main(String[] args) {
        Image img = new ImageProxy("photo.jpg");
        img.display(); // File is loaded only here
    }
}

# Mapping Participants

• Image (Subject): Common interface.
• HighResImage (RealSubject): Expensive operation.
• ImageProxy: Substitute with lazy loading.

# Conclusions

Efficient solution to manage expensive resources, loading them only when necessary, improving performance and user experience.

# Related Patterns