The Facade pattern provides a unified, simplified interface to a set of interfaces in a subsystem, making it easier to use.

Problem

A subsystem has many classes and complex interactions, but clients only need a small subset of functionality.

Solution 

  // Complex subsystem
class VideoFile { /* ... */ }
class AudioMixer { void mix() { } }
class VideoCodec { void decode(VideoFile f) { } }
class BitrateReader { void read(VideoFile f) { } }

// Facade — simplified interface
class VideoConverter {
    public File convert(VideoFile source, String format) {
        AudioMixer mixer = new AudioMixer();
        VideoCodec codec = new VideoCodec();
        BitrateReader reader = new BitrateReader();

        reader.read(source);
        codec.decode(source);
        mixer.mix();
        // ... complex conversion logic

        return new File("converted." + format);
    }
}

// Client — simple usage
VideoConverter converter = new VideoConverter();
File result = converter.convert(videoFile, "mp4");

Java Examples 

  // SLF4J is a facade over Log4j, Logback, JUL
Logger log = LoggerFactory.getLogger(MyClass.class);

// JPA EntityManager hides JDBC complexity
entityManager.persist(user);

// Spring JdbcTemplate simplifies JDBC
jdbcTemplate.queryForObject("SELECT count(*) FROM users", Integer.class);

// HttpClient (Java 11+) simplifies HTTP operations
HttpClient.newHttpClient().send(request, HttpResponse.BodyHandlers.ofString());

Facade vs Adapter vs Decorator

Pattern Purpose
Facade Simplify a complex subsystem
Adapter Convert one interface to another
Decorator Add behavior to an object

When to Use

  • Subsystem is complex and clients need a simple entry point
  • You want to decouple clients from subsystem internals
  • Layering — facade defines the boundary between layers

Best Practices

  • Facade should not contain business logic — delegate to subsystem
  • One facade per subsystem — do not create a god class
  • Clients can still access subsystem directly if needed
  • Common in service layers: OrderService facades over repository, payment, and notification subsystems