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JDBC Connection Pooling

~1 min read · Java
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What is Connection Pooling?

Connection Pooling is a technique used in JDBC to manage and reuse database connections efficiently. Instead of creating and closing connections for every request, a pool of connections is maintained and reused, improving performance and resource utilization.

Why Use Connection Pooling?

✔ Reduces overhead of repeatedly creating and closing database connections.

✔ Improves performance by reusing connections.

✔ Handles concurrent database access efficiently.

✔ Manages connection limits efficiently in multi-threaded environments.

How Connection Pooling Works?

  1. A pool of database connections is created at application startup.
  2. When an application needs a database connection, it borrows one from the pool.
  3. After completing the operation, the connection is returned to the pool for reuse.
  4. If all connections are busy, a new connection is created (if within the limit) or the request waits until a connection is available.

Implementing Connection Pooling in JDBC

There are multiple ways to implement connection pooling in Java JDBC, using:

  • Apache DBCP (Database Connection Pooling)
  • HikariCP (Fastest & Recommended)
  • C3P0
  • BoneCP
  • Tomcat JDBC Connection Pool

Connection Pooling Using HikariCP (Recommended):

✔ Static block initializes the connection pool at application startup.

✔ HikariConfig sets connection pooling properties like maxPoolSize, idleTimeout, etc.

✔ getConnection() method fetches a connection from the pool.

✔ Try-with-resources ensures proper connection closing after use.

import com.zaxxer.hikari.HikariConfig; import com.zaxxer.hikari.HikariDataSource; import java.sql.Connection; import java.sql.SQLException; public class HikariCPExample { private static HikariDataSource dataSource; static { HikariConfig config = new HikariConfig(); config.setJdbcUrl("jdbc:mysql://localhost:3306/mydb"); config.setUsername("root"); config.setPassword("password"); config.setMaximumPoolSize(10); // Max connections in the pool config.setMinimumIdle(5); // Minimum idle connections config.setIdleTimeout(30000); // 30 seconds idle timeout config.setMaxLifetime(1800000); // 30 minutes max lifetime dataSource = new HikariDataSource(config); } public static Connection getConnection() throws SQLException { return dataSource.getConnection(); } public static void main(String[] args) { try (Connection connection = getConnection()) { if (connection != null) { System.out.println("✅ Connection successful using HikariCP!"); } } catch (SQLException e) { e.printStackTrace(); } } }

Connection Pooling Using Apache DBCP:

✔ Works similarly to HikariCP but is slightly slower.

import org.apache.commons.dbcp2.BasicDataSource; import java.sql.Connection; import java.sql.SQLException; public class DBCPExample { private static BasicDataSource dataSource; static { dataSource = new BasicDataSource(); dataSource.setUrl("jdbc:mysql://localhost:3306/mydb"); dataSource.setUsername("root"); dataSource.setPassword("password"); dataSource.setMinIdle(5); dataSource.setMaxIdle(10); dataSource.setMaxOpenPreparedStatements(100); } public static Connection getConnection() throws SQLException { return dataSource.getConnection(); } public static void main(String[] args) { try (Connection connection = getConnection()) { if (connection != null) { System.out.println("✅ Connection successful using Apache DBCP!"); } } catch (SQLException e) { e.printStackTrace(); } } }

Configure C3P0 Connection Pool:

✔ C3P0 is slower but easy to configure.

import com.mchange.v2.c3p0.ComboPooledDataSource; import java.sql.Connection; import java.sql.SQLException; public class C3P0Example { private static ComboPooledDataSource dataSource = new ComboPooledDataSource(); static { try { dataSource.setDriverClass("com.mysql.cj.jdbc.Driver"); dataSource.setJdbcUrl("jdbc:mysql://localhost:3306/mydb"); dataSource.setUser("root"); dataSource.setPassword("password"); dataSource.setMinPoolSize(5); dataSource.setMaxPoolSize(20); dataSource.setAcquireIncrement(5); } catch (Exception e) { e.printStackTrace(); } } public static Connection getConnection() throws SQLException { return dataSource.getConnection(); } public static void main(String[] args) { try (Connection connection = getConnection()) { if (connection != null) { System.out.println("✅ Connection successful using C3P0!"); } } catch (SQLException e) { e.printStackTrace(); } } }

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