Structural_Facade Pattern

✅ Facade

• provide a 👍🏻 simplified, unified interface to a 👎🏻 complex subsystem
• define a high level interface

• that makes the subsystem easier to use

• 👎🏻 client interacts with many classes and complicated workflow
• 👍🏻 client just interacts with single facade class

• facade class does all the underlying difficult job, coordiate the sub components

• 👀 Like having a remote control in a smart home
• to control lights, speaker, caldera…

✅ Diagram

👀

✔️ sub types of file

• has class of file reading, writing and deleting

class FileReader {
    public String readFile(String filePath){
        //read file function
    }
}

class FileWriter {
    public void writeFile(String filePath, String content){
      //write file function
    }
}

class FileDeleter {
    public void deleteFile(String filePath){
      //delete file function
    }
}

✔️ Fascade class

• like a remote control that controls everything related to files

class FileSystemFacade {
    private FileReader fileReader;
    private FileWriter fileWriter;
    private FileDeleter fileDeleter;

    public FileSystemFacade() {
       //constructor
    }

    public String readFile(String filePath) {
      //manage read file
      fileReader.readFile(filePath)
    }

    public boolean writeFile(String filePath, String content) {
        //manage write file
        fileWriter.writeFile(filePath, content);
    }

    public boolean deleteFile(String filePath) {
        //maange delete file
        fileDeleter.deleteFile(filePath);
    }
}

✔️ Main class

// 👎🏻 before
// client has to know
FileWriter fileWrite = new FileWriter();
fileWrite.writeFile(); //need to write each subsystem
FileReader fileRead = new FileReader();
fileRead.readFile();

// 👍🏻 after
// client just has to call FileSystemFacade class
// FileSystemFacade will do everything!

FileSystemFacade fs = new FileSystemFacade();

// Write to file
fs.writeFile();

// Read from file
fs.readFile("test.txt");

// Delete file
fs.deleteFile("test.txt");

🛠️

• Logger Factory
• Logger logger = LoggerFactory.getLogger(MyClass.class);

• LoggerFactory acts as a facade over different logging implementations

• DriverManager
• Connection conn = DriverManager.getConnection(url);
• DriverManager acts as a facade for DB drivers