Describe the lifecycle of a WebSocket in a Java web application.
- Connect, Communicate, Disconnect
- Create, Transmit, Terminate
- Handshake, Data Transfer, Termination
- Initialization, Open, Close
The lifecycle of a WebSocket in a Java web application involves a handshake phase, followed by data transfer, and finally, termination. This sequence includes establishing the connection, exchanging data, and closing the connection.
A WebSocket connection is established with a _________ handshake upgraded from an HTTP connection.
- SSL/TLS
- TCP
- UDP
- WebSocket
A WebSocket connection is established with a "WebSocket" handshake upgraded from an HTTP connection.
In Java EE, the _________ method is used to send a message to the connected WebSocket client.
- broadcastMessage()
- sendMessage()
- sendText()
- writeMessage()
In Java EE, the sendMessage() method is used to send a message to the connected WebSocket client.
The annotation _________ is used to configure the endpoint of a WebSocket server.
- @EndpointConfig
- @ServerEndpoint
- @WebSocketConfig
- @WebSocketEndpoint
The annotation @ServerEndpoint is used to configure the endpoint of a WebSocket server.
A servlet receives a POST request with JSON data. What are the steps to correctly parse and use this data?
- Use the doGet() method and manually parse the JSON data using a JSON library.
- Use the doGet() method and rely on the servlet container to automatically parse the JSON data.
- Use the doPost() method and manually parse the JSON data using a JSON library.
- Use the doPost() method and rely on the servlet container to automatically parse the JSON data.
When handling a POST request with JSON data, it is appropriate to use the doPost() method, and manual parsing is often necessary using a JSON library. The servlet container does not automatically parse JSON data.
The _________ interface in Java EE allows the server to react to WebSocket lifecycle events.
- Decoder
- Encoder
- Endpoint
- Session
The Endpoint interface in Java EE allows the server to react to WebSocket lifecycle events.
To handle binary data in a WebSocket, the _________ method is typically implemented.
- onBinaryMessage
- onClose
- onError
- onTextMessage
To handle binary data in a WebSocket, the onBinaryMessage method is typically implemented.
What happens if the init() method of a Servlet throws an exception?
- Servlet becomes inactive
- Servlet continues to initialize
- Servlet fails to initialize
- Servlet restarts
If the init() method of a Servlet throws an exception, the servlet fails to initialize, and the servlet container may mark the servlet as unavailable.
A high-frequency trading application needs to send and receive financial data with minimal latency. What WebSocket features make it suitable for this application?
- Caching and client-side data storage
- Long polling and server-sent events
- Multiplexing and low latency
- Request-response pattern and reliable message delivery
WebSockets, with features like multiplexing and low latency, are suitable for high-frequency trading applications, as they enable efficient, bidirectional communication with minimal delay in data transmission.
What is a common practice to reduce the load on a servlet?
- Caching
- Database Connection Pooling
- Lazy Loading
- Multithreading
Database Connection Pooling is a common practice to reduce the load on a servlet by efficiently managing and reusing database connections, improving performance.