JDBC & Database Connectivity Interview Questions

JDBC (Java Database Connectivity) is an API that enables Java applications to connect to and interact with relational databases.

JDBC architecture consists of Java applications, JDBC API, DriverManager, JDBC drivers, and the database.

The four JDBC driver types are JDBC-ODBC Bridge, Native Driver, Network Protocol Driver, and Thin Driver.

Load the JDBC driver, establish a connection using DriverManager, create a statement, execute queries, and close resources.

DriverManager manages JDBC drivers and establishes database connections.

Connection represents an active connection to a database and provides methods for transaction management and statement creation.

Statement is used to execute static SQL queries against a database.

PreparedStatement is precompiled, supports parameters, improves performance, and helps prevent SQL injection.

CallableStatement is used to execute stored procedures in a database.

ResultSet is an object that stores and allows navigation through data returned by a SQL query.

ResultSet types include TYPE_FORWARD_ONLY, TYPE_SCROLL_INSENSITIVE, and TYPE_SCROLL_SENSITIVE.

Batch processing groups multiple SQL statements into a single database call for improved performance.

Transaction management ensures that a set of database operations are executed as a single logical unit.

commit() permanently saves transaction changes, while rollback() undoes changes since the last commit.

SQL Injection can be prevented by using PreparedStatement, parameterized queries, and input validation.

Name concrete APIs (collections, concurrency, streams, annotations) tied to JDBC & Database Connectivity. Interviewers want syntax-level clarity plus when you would reach for each feature in production.

Prefer specific checked/unchecked exceptions, wrap lower-level failures with context, and avoid empty catch blocks. For JDBC & Database Connectivity, decide what is recoverable vs fatal to the request thread.

JUnit 5 with Arrange-Act-Assert, Mockito for collaborators, and parameterized tests for edge cases. Keep JDBC & Database Connectivity logic pure where possible so tests stay fast.

Incorrect equals/hashCode break HashMap/HashSet behavior. If JDBC & Database Connectivity stores objects in collections, explain the contract and mutability pitfalls.

Retain only needed references, prefer streaming for large datasets, and avoid accidental caches. Relate leaks or GC pressure to a concrete JDBC & Database Connectivity scenario.