Java Database Connectivity (JDBC)
Java Database Connectivity (JDBC) is an API for connecting and executing database queries in Java. It provides a standard interface for Java applications to interact with various database management systems (DBMS).
Detailed Description of JDBC Working Mechanism and Key Components:
- JDBC Driver: Implementations provided by database vendors to connect to different types of databases. For example, Oracle and MySQL have their own JDBC drivers.
- Connecting to Database: Use the
DriverManager
class to establish a connection to the database by providing the database URL, username, and password. - Executing SQL Statements: Use
Statement
,PreparedStatement
, andCallableStatement
objects to execute SQL statements.Statement
executes static SQL statements.PreparedStatement
executes parameterized SQL statements.CallableStatement
executes stored procedures.
- Handling Result Sets: After executing a query (SELECT statement), a
ResultSet
object is returned, containing the query results. You can traverse this result set to retrieve data. - Closing Connections: After database operations are complete, close the
ResultSet
,Statement
, and database connection to release resources.close()
: Immediately release the database and JDBC resources held by thisConnection
object rather than waiting for them to be automatically released.
- Transaction Management: JDBC supports transactions, which can be controlled by the database connection to start, commit, and roll back transactions.
setAutoCommit(boolean autoCommit)
: Set whether the connection’s transactions are automatically committed.commit()
: Commit the current transaction.rollback()
: Roll back the current transaction.
- Exception Handling: JDBC operations can throw
SQLException
. Proper handling of these exceptions is crucial for building robust database applications.
A Basic JDBC Usage Example
In this example, we connect to a MySQL database, execute a query, and print the data from the result set. Note that in a real application, you should handle exceptions properly and ensure resources are released correctly.
1 | import java.sql.*; |