Deep Dive into smart‑socket’s Built‑In Plugin System

Plugin Architecture

smart‑socket plugin system is based on the Plugin interface, which extends NetMonitor . It defines three extension points:

preProcess : preprocesses a request message and decides whether the message should continue to MessageProcessor.process. Returning false drops the message.

stateEvent : listens to state‑machine events for a session.

NetMonitor methods: monitor connection acceptance, read/write operations, etc.

public interface Plugin<T> extends NetMonitor {
    boolean preProcess(AioSession session, T t);
    void stateEvent(StateMachineEnum stateMachineEnum, AioSession session, Throwable throwable);
}

To simplify development, AbstractPlugin provides empty implementations of all Plugin methods.

public abstract class AbstractPlugin<T> implements Plugin<T> {
    @Override public boolean preProcess(AioSession session, T t) { return true; }
    @Override public void stateEvent(StateMachineEnum stateMachineEnum, AioSession session, Throwable throwable) {}
    // other NetMonitor methods have empty bodies
}

Plugins are added to a MessageProcessor via addPlugin and the processor is passed to an AioQuickServer instance.

MessageProcessor<String> processor = new AbstractMessageProcessor<>() {
    @Override public void process0(AioSession session, String msg) {
        // handle message
    }
};
processor.addPlugin(new SslPlugin<>());
processor.addPlugin(new HeartPlugin<>());
AioQuickServer<String> server = new AioQuickServer<>(8888, new StringProtocol(), processor);
server.start();

SSL/TLS Security Plugin

SslPlugin provides SSL/TLS encryption by wrapping the underlying AsynchronousSocketChannel.

public class SslServerExample {
    public static void main(String[] args) throws Exception {
        MessageProcessor<String> processor = new AbstractMessageProcessor<>() {
            @Override public void process0(AioSession session, String msg) {
                System.out.println("Received encrypted message: " + msg);
            }
        };
        ServerSSLContextFactory factory = new ServerSSLContextFactory();
        factory.keystore("keystore.jks", "password");
        SslPlugin<String> sslPlugin = new SslPlugin<>(factory);
        processor.addPlugin(sslPlugin);
        AioQuickServer<String> server = new AioQuickServer<>(8888, new StringProtocol(), processor);
        server.start();
    }
}

Heartbeat Detection Plugin

HeartPlugin detects active connections and prevents dead connections caused by network anomalies.

public class CustomHeartPlugin extends HeartPlugin<String> {
    public CustomHeartPlugin() {
        super(30, 60, TimeUnit.SECONDS); // interval 30 s, timeout 60 s
    }
    @Override public void sendHeartRequest(AioSession session) throws IOException {
        byte[] heartMsg = "PING".getBytes();
        session.writeBuffer().writeInt(heartMsg.length);
        session.writeBuffer().write(heartMsg);
    }
    @Override public boolean isHeartMessage(AioSession session, String msg) {
        return "PING".equals(msg) || "PONG".equals(msg);
    }
}

public class HeartPluginExample {
    public static void main(String[] args) throws IOException {
        MessageProcessor<String> processor = new AbstractMessageProcessor<>() {
            @Override public void process0(AioSession session, String msg) {
                if ("PING".equals(msg)) {
                    byte[] resp = "PONG".getBytes();
                    session.writeBuffer().writeInt(resp.length);
                    session.writeBuffer().write(resp);
                    session.writeBuffer().flush();
                } else {
                    System.out.println("Received message: " + msg);
                }
            }
        };
        processor.addPlugin(new CustomHeartPlugin());
        AioQuickServer<String> server = new AioQuickServer<>(8888, new StringProtocol(), processor);
        server.start();
    }
}

Blacklist Plugin

BlackListPlugin rejects connections from specific IP addresses or port ranges.

public class BlackListExample {
    public static void main(String[] args) throws IOException {
        MessageProcessor<String> processor = new AbstractMessageProcessor<>() {
            @Override public void process0(AioSession session, String msg) {
                System.out.println("Received message: " + msg);
            }
        };
        BlackListPlugin<String> blackListPlugin = new BlackListPlugin<>();
        // Reject a specific IP
        blackListPlugin.addRule(address -> !"192.168.1.100".equals(address.getAddress().getHostAddress()));
        // Reject ports outside 10000‑20000
        blackListPlugin.addRule(address -> {
            int port = address.getPort();
            return port < 10000 || port > 20000;
        });
        processor.addPlugin(blackListPlugin);
        AioQuickServer<String> server = new AioQuickServer<>(8888, new StringProtocol(), processor);
        server.start();
    }
}

Memory‑Pool Monitoring Plugin

BufferPageMonitorPlugin monitors the usage of the memory pool.

public class BufferPageMonitorExample {
    public static void main(String[] args) throws IOException {
        MessageProcessor<String> processor = new AbstractMessageProcessor<>() {
            @Override public void process0(AioSession session, String msg) {
                System.out.println("Received message: " + msg);
            }
        };
        AioQuickServer<String> server = new AioQuickServer<>(8888, new StringProtocol(), processor);
        // Output memory‑pool status every 6 seconds
        processor.addPlugin(new BufferPageMonitorPlugin<>(server, 6));
        server.start();
    }
}

Traffic Monitoring Plugin

StreamMonitorPlugin logs the data flow of the network layer, showing hex dumps in real time.

public class StreamMonitorExample {
    public static void main(String[] args) throws IOException {
        MessageProcessor<String> processor = new AbstractMessageProcessor<>() {
            @Override public void process0(AioSession session, String msg) {
                System.out.println("Received message: " + msg);
            }
        };
        processor.addPlugin(new StreamMonitorPlugin<>());
        AioQuickServer<String> server = new AioQuickServer<>(8888, new StringProtocol(), processor);
        server.start();
    }
}

Sample console output:

2023-01-01 10:00:00.123 [ /127.0.0.1:56789 --> /127.0.0.1:8888 ] [ read: 12 bytes ]
00000000h: 48 65 6c 6c 6f 20 57 6f 72 6c 64 21   ; Hello World!

Socket Option Plugin

SocketOptionPlugin configures various socket options.

public class SocketOptionExample {
    public static void main(String[] args) throws IOException {
        MessageProcessor<String> processor = new AbstractMessageProcessor<>() {
            @Override public void process0(AioSession session, String msg) {
                System.out.println("Received message: " + msg);
            }
        };
        SocketOptionPlugin<String> socketOptionPlugin = new SocketOptionPlugin<>();
        socketOptionPlugin.setOption(StandardSocketOptions.SO_KEEPALIVE, true);
        socketOptionPlugin.setOption(StandardSocketOptions.SO_RCVBUF, 1024 * 1024);
        socketOptionPlugin.setOption(StandardSocketOptions.SO_SNDBUF, 1024 * 1024);
        processor.addPlugin(socketOptionPlugin);
        AioQuickServer<String> server = new AioQuickServer<>(8888, new StringProtocol(), processor);
        server.start();
    }
}

Idle‑State Plugin

IdleStatePlugin detects idle connections and automatically closes them after a configured period without read/write activity.

public class IdleStateExample {
    public static void main(String[] args) throws IOException {
        MessageProcessor<String> processor = new AbstractMessageProcessor<>() {
            @Override public void process0(AioSession session, String msg) {
                System.out.println("Received message: " + msg);
            }
        };
        // Close connection if idle for 60 seconds
        processor.addPlugin(new IdleStatePlugin<>(60));
        AioQuickServer<String> server = new AioQuickServer<>(8888, new StringProtocol(), processor);
        server.start();
    }
}

Plugin Execution Order

Plugins execute in the order they are added. If any plugin’s preProcess returns false, subsequent plugins are skipped and the message is not passed to the MessageProcessor.

// Example order
processor.addPlugin(plugin1); // executed first
processor.addPlugin(plugin2); // executed second
processor.addPlugin(plugin3); // executed last

Best‑Practice Recommendations

Use plugins wisely: select only needed plugins to avoid unnecessary performance overhead.

Mind plugin order: execution order can affect functionality; arrange accordingly.

Custom plugin development: inherit AbstractPlugin for special requirements.

Monitor plugin performance: monitoring plugins may introduce overhead; balance monitoring needs with performance.

Exception handling: handle exceptions inside plugins to prevent disruption of the main processing flow.