What are the implications of using optimistic vs. pessimistic locking strategies in database transactions?
- Both have similar implications
- Optimistic locking prevents blocking, may lead to conflicts
- Pessimistic locking reduces contention, but can cause blocking
- They are used interchangeably based on convenience
Optimistic locking in database transactions prevents blocking but may lead to conflicts, while pessimistic locking reduces contention but can cause blocking due to exclusive locks.
How does the use of 'lazy loading' in an ORM framework like Hibernate affect database performance?
- Decreases performance by loading all data at once
- Depends on the specific use case
- Has no impact on performance
- Increases performance by loading data on demand
'Lazy loading' in Hibernate increases performance by loading data on demand, reducing the initial load time and resource consumption.
How does transaction isolation level impact database performance and consistency?
- Control concurrency issues
- Ensure data consistency
- Increase transaction throughput
- Read uncommitted data
The transaction isolation level in JDBC determines the degree to which one transaction can affect another. Choosing the appropriate isolation level balances performance and consistency. Lower levels improve performance but may introduce consistency issues, while higher levels enhance consistency at the expense of performance.
What is the advantage of using CallableStatement in JDBC?
- Execute SQL queries with parameters
- Execute stored procedures
- Improve connection pooling
- Streamline complex transactions
The CallableStatement in JDBC is used to execute stored procedures, providing a way to encapsulate and execute multiple SQL statements as a single unit. This enhances code modularity, reusability, and security by allowing the use of stored procedures in the database.
When should you choose PreparedStatement over Statement in JDBC?
- Execute multiple queries efficiently
- Execute parameterized queries
- Improve query optimization
- Simplify complex join operations
The PreparedStatement in JDBC is used to execute parameterized queries, which helps prevent SQL injection and improves performance by reusing the compiled query plan. It is suitable when you need to execute the same SQL statement multiple times with different parameters.
What is the primary purpose of using a connection pool in database interactions?
- Ensuring database security
- Managing database connections
- Optimizing SQL queries
- Reducing database load
The primary purpose of using a connection pool is to manage and reuse database connections efficiently, reducing the overhead of opening and closing connections for each database interaction.
Which method is used to batch multiple SQL statements before sending them to the database?
- execute()
- executeBatch()
- executeQuery()
- executeUpdate()
The executeBatch() method is used to batch multiple SQL statements together before sending them to the database, which can improve performance by reducing the number of round-trips.
In a scenario where a transaction involves multiple SQL queries, how should exceptions be handled to ensure that either all queries succeed or none do?
- Commit each query individually
- Commit the entire transaction only if all queries succeed
- Ignore exceptions and continue with the transaction
- Rollback the entire transaction on any exception
Handling exceptions in a transaction involving multiple SQL queries requires rolling back the entire transaction on any exception to ensure data consistency鈥攅ither all queries succeed, or none do.
How is an asynchronous task started in a servlet?
- asyncTask.start()
- beginAsync()
- initAsync()
- startAsync()
An asynchronous task in a servlet is started using the startAsync() method. This method initiates asynchronous processing and returns an AsyncContext for managing the asynchronous task.
What enables servlets to handle requests asynchronously?
- Asynchronous Servlets
- Event Listeners
- RequestDispatcher
- Servlet Containers
Servlets handle requests asynchronously through the use of Asynchronous Servlets, allowing them to perform tasks concurrently without blocking the processing of other requests.
When designing a system for reporting purposes, what techniques would you use to ensure minimal impact on the transactional database system?
- Caching, Denormalization, Stored Procedures, Asynchronous Processing
- Data Warehousing, Materialized Views, Scheduled ETL Processes, Read-Only Replicas
- Indexing, Query Optimization, Database Partitioning, Load Balancing
- Vertical Scaling, Horizontal Scaling, Compression, Normalization
Techniques like data warehousing, materialized views, scheduled ETL processes, and read-only replicas can help ensure minimal impact on the transactional database system in a reporting system.
What is the role of the doHead method in HTTP servlets?
- It handles HEAD requests.
- It is invoked after the doGet method.
- It is used for handling GET requests.
- It processes the HTTP headers.
The doHead method in HTTP servlets is used to process the HTTP headers. It does not have a body, making it suitable for handling requests where only the headers need to be processed without returning a full response body.