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SUBSCRIBE NOWDecoupling Abstraction and Implementation
The Bridge Design Pattern separates an abstraction from its underlying implementation, allowing both class hierarchies to vary independently. In real-world enterprise applications, hardcoding messaging channels directly into message types leads to tight coupling and unnecessary subclass proliferation.
By utilizing object composition instead of deep inheritance, the Bridge pattern provides a clean, maintainable structure where message categories and delivery transports remain loosely coupled.
Complete Java Code Walkthrough
Here is an end-to-end implementation illustrating message sending across multiple delivery channels using the Bridge pattern:
// 1. Implementor Interface
interface MessageSender {
void sendMessage(String message);
}
// 2. Concrete Implementors
class EmailSender implements MessageSender {
@Override
public void sendMessage(String message) {
System.out.println("Email: Sending -> " + message);
}
}
class SmsSender implements MessageSender {
@Override
public void sendMessage(String message) {
System.out.println("SMS: Sending -> " + message);
}
}
// 3. Abstraction
abstract class Message {
protected MessageSender messageSender;
public Message(MessageSender messageSender) {
this.messageSender = messageSender;
}
public abstract void send(String content);
}
// 4. Refined Abstraction
class UrgentMessage extends Message {
public UrgentMessage(MessageSender messageSender) {
super(messageSender);
}
@Override
public void send(String content) {
messageSender.sendMessage("[URGENT ALERT] " + content);
}
}
class NormalMessage extends Message {
public NormalMessage(MessageSender messageSender) {
super(messageSender);
}
@Override
public void send(String content) {
messageSender.sendMessage("[INFO] " + content);
}
}
// 5. Client Application
public class MessageBridgeDemo {
public static void main(String[] args) {
// Send urgent alert via SMS
MessageSender sms = new SmsSender();
Message alert = new UrgentMessage(sms);
alert.send("Server CPU usage exceeded 90%!");
// Send regular information via Email
MessageSender email = new EmailSender();
Message newsletter = new NormalMessage(email);
newsletter.send("Weekly engineering updates are published.");
}
}Key Architectural Takeaways
- Composition Over Inheritance: Avoids multi-level inheritance hierarchies and messy diamond problem dilemmas.
- Runtime Flexibility: Different message sender channels can be swapped dynamically based on system rules or user configurations.
- Seamless Extensibility: Introducing a new message type (such as EncryptedMessage) or transport medium (such as SlackSender) requires zero modifications to existing classes.
Watch More Related Design Pattern Tutorials
Click here to watch in Youtube : https://www.youtube.com/watch?v=Sqpgv1QMIPk
Click the below Image to Enlarge
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| Bridge Design pattern - Implementation [Send Message] |
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| Bridge Design pattern - Implementation [Send Message] - Class Diagram |
MessageSender.java
public interface MessageSender
{
public void sendMessage(String message);
}
SmsMessageSender.java
public class SmsMessageSender implements MessageSender
{
public void sendMessage(String message)
{
System.out.println("'"+message+ "' : This Message has been sent using SMS");
}
}
EmailMessageSender.java
public class EmailMessageSender implements MessageSender
{
public void sendMessage(String message)
{
System.out.println("'"+message+ "' : This Message has been sent using Email");
}
}
Message.java
abstract class Message
{
protected MessageSender messageSender;
abstract public void sendMessage(String message);
}
ShortMessage.java
public class ShortMessage extends Message
{
public ShortMessage(MessageSender messageSender)
{
super.messageSender = messageSender;
}
@Override
public void sendMessage(String message)
{
if(message.length()<=5)
{
messageSender.sendMessage(message);
}
else
{
System.out.println("Sorry cannot send the message.....");
}
}
}
LongMessage.java
public class LongMessage extends Message
{
public LongMessage(MessageSender messageSender)
{
super.messageSender = messageSender;
}
@Override
public void sendMessage(String message)
{
messageSender.sendMessage(message);
}
}
Client.java
import java.util.Scanner;
public class Client
{
public static void main(String[] args)
{
System.out.println("Do you want to send 'longmessage' or 'shortmessage' ?");
Scanner scanner = new Scanner(System.in);
String messageType = scanner.next();
System.out.println("Please enter the message you want to send");
Scanner scanner1 = new Scanner(System.in);
String message = scanner1.nextLine();
if (messageType.equalsIgnoreCase("longmessage"))
{
Message longMessage = new LongMessage(new EmailMessageSender());
longMessage.sendMessage(message);
}
else
{
Message shortMessage = new ShortMessage(new SmsMessageSender());
shortMessage.sendMessage(message);
}
}
}
Output
Do you want to send 'longmessage' or 'shortmessage' ?
longmessage
Please enter the message you want to send
Hello how are you ? when did you come?
'Hello how are you ? when did you come?' : This Message has been sent using Email
Do you want to send 'longmessage' or 'shortmessage' ?
shortmessage
Please enter the message you want to send
hi
'hi' : This Message has been sent using SMS
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