JDBC 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?

A pool of database connections is created at application startup.
When an application needs a database connection, it borrows one from the pool.
After completing the operation, the connection is returned to the pool for reuse.
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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