WebSocket client API in the Java class library: advanced usage
WebSocket client API in the Java class library: advanced usage
WebSocket is a protocol that allows two -way communication between clients and servers.The WebSocket client API in the Java class library provides developers' ability to quickly realize the WebSocket client in the Java program.In addition to basic connection and sending message functions, this API also provides some advanced usage to meet more complicated needs.
1. Connection management
In the WebSocket client API, connection management is an important issue.In practical applications, we may need to establish a connection with multiple servers at the same time, or to automatically connect to the server.In order to achieve these functions, Java provides `Endpoint` and` Clienendpoint`, which represent the WebSocket client and client endpoint respectively.
The following is an example code that uses the `Endpoint` class to create a WebSocket client:
@ClientEndpoint
public class MyWebSocketClient {
private Session session;
@OnOpen
public void onOpen(Session session) {
System.out.println ("Connection has been established");
this.session = session;
}
@OnMessage
public void onMessage(String message) {
System.out.println ("Receive messages:" + message);
}
@OnClose
public void onClose(Session session, CloseReason closeReason) {
System.out.println ("Connection has been closed:" + Closereason);
this.session = null;
}
public void sendMessage(String message) {
if (session != null && session.isOpen()) {
session.getAsyncRemote().sendText(message);
}
}
public void close() {
if (session != null && session.isOpen()) {
try {
session.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
In this example, we marked the `MywebsocketClient` class as a WebSocket client through the`@clientenpoint` annotation.The annotations of ``@onopen`, ``@onmessage` and `@onClose` respectively represent the callback method when connected, received messages, and connect to close, respectively.The `session` class represents the connection session with the server, and we can send and receive messages through it.
2. Custom message processing
The WebSocket client API also allows us to customize the message processor in order to handle messages sent by the server more flexibly.By implementing the `OnMessage` method of the` Messagehandler` interface, we can customize the logic of message processing.
The following is an example code that shows how to customize the message processor:
public class MyMessageHandler implements MessageHandler.Partial<String> {
@Override
public void onMessage(String message, boolean last) {
System.out.println ("Receive messages:" + message + ", last:" + last);
// Add customized message processing logic here
}
}
We can set this custom message processor in the client initialization code:
MyMessageHandler messageHandler = new MyMessageHandler();
session.addMessageHandler(messageHandler);
Third, error treatment
In the development of the WebSocket client, error treatment is an important aspect.Java's WebSocket client API provides a `Onerror` annotation, we can use it to handle the error.
The following is an example code that shows how to deal with connection errors:
@ClientEndpoint
public class MyWebSocketClient {
// ...
@OnError
public void onError(Session session, Throwable error) {
System.out.println ("connection error:" + error.getMessage ());
}
// ...
}
In this example, we define an error processing method through the annotation of `@onerror`. When the connection occurs, this method is called.We can perform some error -processed logic in this method, such as re -connection or printing wrong logs.
Summarize:
The WebSocket client API in the Java class library provides a series of advanced usage to meet more complicated needs.By using Endpoint, custom message processing, and error processing, we can develop powerful and flexible WebSocket client applications.It is hoped that the knowledge provided in this article can help readers better understand and use the WebSocket client API in the Java class library.
