WebSockets & Real-Time Systems with Spring · Aula

Intercetores WebSocket

Utilize intercetores WebSocket para efetuar o pré-processamento e o pós-processamento de mensagens e eventos de ligação.

Intercetores WebSocket é uma aula grátis de WebSockets & Real-Time Systems with Spring no CoddyKit. Esta é a aula 1 de 4. Você pode ler a aula completa abaixo gratuitamente — depois pratica ao vivo no navegador com um editor de código integrado e um tutor de IA 24/7. Faz parte do caminho de aprendizado de WebSockets & Real-Time Systems with Spring, e seu progresso é sincronizado entre a web e o app CoddyKit. O curso de WebSockets & Real-Time Systems with Spring inclui 4 aulas no total.

Partes desta aula ainda não foram traduzidas e aparecem em inglês.

Welcome to Interceptors!

In Spring WebSockets, Interceptors act like gatekeepers or event listeners that can observe and modify the WebSocket lifecycle.

They allow you to perform actions like logging, authentication, or modifying data at specific points during a connection or message exchange.

Lifecycle Hooks

Think of the WebSocket process:

Handshake: Initial HTTP request to upgrade to WebSocket.
Connection: WebSocket link is established.
Message Exchange: Data flows between client and server.
Disconnection: WebSocket link closes.

Interceptors let you "hook" into these stages.

Intercepting the Handshake

The HandshakeInterceptor is crucial for the very first step: the WebSocket handshake.

It lets you:

Inspect the HTTP request before the WebSocket connection is established.
Perform authentication or authorization checks.
Add attributes to the WebSocket session.

You can decide whether to allow the handshake to proceed.

Coding a Handshake Interceptor

Let's create a simple HandshakeInterceptor that logs when a connection attempt begins and ends. This is useful for monitoring or debugging.

Notice the beforeHandshake and afterHandshake methods.

import org.springframework.http.server.ServerHttpRequest;
import org.springframework.http.server.ServerHttpResponse;
import org.springframework.web.socket.WebSocketHandler;
import org.springframework.web.socket.server.HandshakeInterceptor;
import java.util.Map;

public class MyHandshakeInterceptor implements HandshakeInterceptor {

  @Override
  public boolean beforeHandshake(ServerHttpRequest request, ServerHttpResponse response,
                                 WebSocketHandler wsHandler, Map<String, Object> attributes) throws Exception {
    System.out.println(">>> Handshake starting for: " + request.getURI());
    // 'attributes' map can be used to pass data to WebSocket session
    return true; // Allow handshake to proceed
  }

  @Override
  public void afterHandshake(ServerHttpRequest request, ServerHttpResponse response,
                             WebSocketHandler wsHandler, Exception exception) {
    System.out.println("<<< Handshake completed for: " + request.getURI());
    if (exception != null) {
      System.err.println("Handshake failed: " + exception.getMessage());
    }
  }
}

Integrating Handshake Interceptors

To make our MyHandshakeInterceptor active, we need to register it within our Spring Boot application's WebSocket configuration.

Run this code and try connecting to ws://localhost:8080/ws from a browser's developer console (e.g., new WebSocket('ws://localhost:8080/ws')) to see the logs!

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.socket.config.annotation.*;
import org.springframework.web.socket.handler.TextWebSocketHandler;
import org.springframework.http.server.ServerHttpRequest;
import org.springframework.http.server.ServerHttpResponse;
import org.springframework.web.socket.server.HandshakeInterceptor;
import java.util.Map;

@SpringBootApplication
public class Main {
  public static void main(String[] args) {
    SpringApplication.run(Main.class, args);
  }
}

// MyHandshakeInterceptor.java (nested for brevity)
class MyHandshakeInterceptor implements HandshakeInterceptor {
  @Override
  public boolean beforeHandshake(ServerHttpRequest req, ServerHttpResponse res,
                                 org.springframework.web.socket.WebSocketHandler h, Map<String, Object> a) {
    System.out.println(">>> Handshake: " + req.getURI());
    return true;
  }
  @Override
  public void afterHandshake(ServerHttpRequest req, ServerHttpResponse res,
                             org.springframework.web.socket.WebSocketHandler h, Exception e) {
    System.out.println("<<< Handshake done: " + req.getURI());
  }
}

// WebSocketConfig.java (nested for brevity)
@Configuration
@EnableWebSocket
class WebSocketConfig implements WebSocketConfigurer {
  @Override
  public void registerWebSocketHandlers(WebSocketHandlerRegistry r) {
    r.addHandler(new TextWebSocketHandler(), "/ws")
     .addInterceptors(new MyHandshakeInterceptor())
     .setAllowedOrigins("*");
  }
}

Intercepting STOMP Messages

While HandshakeInterceptor handles initial connections, ChannelInterceptor focuses on STOMP messages flowing through Spring's message broker.

These interceptors operate on the messaging channels, allowing you to inspect or modify messages before they reach their destination or after they are sent.

Coding a Channel Interceptor

A ChannelInterceptor provides methods like preSend, postSend, and afterSendCompletion.

The preSend method is commonly used to inspect or modify a message before it is sent to its destination (e.g., a STOMP topic or user queue).

import org.springframework.messaging.Message;
import org.springframework.messaging.MessageChannel;
import org.springframework.messaging.support.ChannelInterceptor;

public class MyChannelInterceptor implements ChannelInterceptor {

  @Override
  public Message<?> preSend(Message<?> message, MessageChannel channel) {
    // Log the message or perform security checks
    System.out.println("Intercepted STOMP message: " + message.getHeaders());
    // You can modify the message here
    return message; // Return the message to proceed
  }

  // Other methods like postSend, afterSendCompletion...
}

Integrating Channel Interceptors

To register a ChannelInterceptor, you typically use a configuration class that extends WebSocketMessageBrokerConfigurer.

Use clientInboundChannel() to intercept messages coming from clients.
Use clientOutboundChannel() to intercept messages going to clients.

This allows fine-grained control over message flow.

Common Use Cases

Interceptors are powerful for many scenarios:

Authentication & Authorization: Validate users before connection or message delivery.
Logging: Track connection events and message traffic.
Session Management: Attach user-specific data to WebSocket sessions.
Message Modification: Add headers, filter content, or transform payloads.
Rate Limiting: Prevent abuse by limiting message frequency.

Interceptor Knowledge Check

You've learned about two main types of WebSocket interceptors in Spring. Let's see if you can distinguish their primary use cases.

Interceptors: Your WebSocket Control

Today, you learned about Spring's WebSocket Interceptors, powerful tools for controlling and observing your real-time communication.

Handshake Interceptors: For pre-connection logic.
Channel Interceptors: For STOMP message flow.

They are essential for building secure, robust, and observable WebSocket applications. Next, we'll explore message converter customization!

Perguntas Frequentes

A aula “Intercetores WebSocket” é grátis?

Sim — o texto completo de “Intercetores WebSocket” é grátis para ler aqui na web. Para praticá-la interativamente (um editor de código integrado e um tutor de IA 24/7) e desbloquear o restante do curso de WebSockets & Real-Time Systems with Spring, atualize para CoddyKit PRO. O curso de WebSockets & Real-Time Systems with Spring inclui 4 aulas no total.

O que vou aprender em “Intercetores WebSocket”?

Utilize intercetores WebSocket para efetuar o pré-processamento e o pós-processamento de mensagens e eventos de ligação. Você pratica WebSockets & Real-Time Systems with Spring com código prático que executa diretamente no navegador, e um tutor de IA 24/7 responde suas dúvidas enquanto trabalha na aula.

Preciso ter experiência prévia para começar WebSockets & Real-Time Systems with Spring?

Nenhuma experiência prévia é necessária. WebSockets & Real-Time Systems with Spring no CoddyKit é estruturado para alunos iniciantes até avançados, então você pode começar aqui ou desde o início e aprender no seu ritmo. Esta é a aula 1 de 4.

Quanto tempo leva a aula “Intercetores WebSocket”?

A maioria das aulas CoddyKit leva cerca de 5–10 minutos. Cada uma é compacta e interativa, então você faz progresso constante e retoma exatamente de onde parou entre web e app.

Posso escrever e executar código nesta aula de WebSockets & Real-Time Systems with Spring?

Sim. Cada aula de WebSockets & Real-Time Systems with Spring inclui um editor de código integrado, então você escreve e executa código real direto no navegador e recebe feedback de IA instantaneamente — nenhuma configuração local necessária.

Todas as aulas deste curso

Intercetores WebSocket
Personalização de conversores de mensagens
Gestão de sessões de utilizador
Mensagens direcionadas a usuários específicos

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