In what scenarios is it safe to have instance variables in a servlet?
- Always safe
- Never safe
- When shared across sessions
- When thread safety is guaranteed
Instance variables in a servlet are safe when they are shared across sessions and thread safety is guaranteed, ensuring that multiple requests can access them concurrently without issues.
The __________ pattern is often used to manage shared resources in a thread-safe manner in servlets.
- Decorator
- Factory
- Observer
- Singleton
The Singleton pattern is often used to manage shared resources in a thread-safe manner in servlets, ensuring that only one instance of the resource is created.
Servlets can be made thread-safe by making shared resources __________.
- abstract
- final
- synchronized
- volatile
Servlets can be made thread-safe by making shared resources synchronized, which ensures that only one thread can access the resource at a time.
Thread safety in servlets can be enhanced by using _________ scoped variables instead of instance variables.
- application
- page
- request
- session
Thread safety in servlets can be enhanced by using application scoped variables instead of instance variables. This ensures shared data is accessible to all users but is stored at the application level, reducing thread safety issues.
In a highly concurrent web application, how would you design a servlet to handle database connections securely and efficiently?
- Open a new database connection for each request.
- Store database connections as static variables.
- Use a connection pool to manage database connections.
- Use synchronized methods for database operations.
Using a connection pool is a best practice in highly concurrent applications as it efficiently manages and shares database connections, reducing the overhead of opening and closing connections for each request.
If a servlet manipulates a shared data structure, what must be done to ensure it operates correctly in a multithreaded environment?
- Avoid multithreading in servlets.
- Synchronize access to the shared data structure.
- Use multiple instances of the servlet.
- Use volatile keyword for the shared data structure.
Synchronizing access to the shared data structure is crucial in a multithreaded environment to prevent data corruption and ensure consistency. The synchronized keyword ensures that only one thread can access the shared data structure at a time.
To handle a POST request, the HttpServlet class uses the _________ method.
- doGet()
- doPost()
- handlePost()
- servicePost()
To handle a POST request, the HttpServlet class uses the doPost() method.
Describe a scenario where it's more efficient to use local variables instead of instance variables in a servlet.
- When the variable is used within a single servlet method.
- When the variable needs to be accessed from different sessions.
- When the variable needs to retain state across multiple requests.
- When the variable should be shared among different servlet instances.
Local variables are more efficient when the variable's scope is limited to a single method and doesn't need to retain state between requests. This reduces the memory footprint and avoids unnecessary storage of data that doesn't persist beyond the method execution.
What is the primary purpose of load balancing in web applications?
- Distribute incoming traffic
- Enhance security
- Execute database queries
- Store session data
The primary purpose of load balancing in web applications is to distribute incoming traffic across multiple servers, ensuring better performance and preventing overload on a single server.
How can an HTTP servlet differentiate between GET and POST requests?
- Checking the request type in the doGet and doPost methods.
- The HTTP servlet cannot differentiate between GET and POST requests.
- Using the HttpServletRequest method getMethod()
- Using the requestType attribute in the web.xml file.
An HTTP servlet can differentiate between GET and POST requests by using the HttpServletRequest method getMethod(), which returns the HTTP method of the request (e.g., "GET" or "POST"). This allows the servlet to determine the type of request being made.