Java如何创建数据库连接池？
本示例说明如何使用ApacheCommonsDBCP库创建连接池实现。
package org.nhooo.example.commons.dbcp;
import org.apache.commons.dbcp2.*;
import org.apache.commons.pool2.impl.GenericObjectPool;
import org.apache.commons.pool2.impl.GenericObjectPoolConfig;
import javax.sql.DataSource;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
public class ConnectionPoolExample {
private static final String URL = "jdbc:mysql://localhost/nhooo";
private static final String USERNAME = "root";
private static final String PASSWORD = "";
private GenericObjectPool<PoolableConnection> connectionPool = null;
public DataSource setUp() {
//创建一个连接工厂对象，该对象将由
//创建连接对象的池。我们通过了
//JDBCURL信息，用户名和密码。
ConnectionFactory cf = new DriverManagerConnectionFactory(
ConnectionPoolExample.URL,
ConnectionPoolExample.USERNAME,
ConnectionPoolExample.PASSWORD);
//创建一个PoolableConnectionFactory，它将包装
//ConnectionFactory创建的要添加的连接对象
//对象池功能。
PoolableConnectionFactory pcf = new PoolableConnectionFactory(cf, null);
pcf.setValidationQuery("SELECT 1");
//创建一个GenericObjectPool实例，其中包含
//连接对象池。
GenericObjectPoolConfig<PoolableConnection> config = new GenericObjectPoolConfig<>();
config.setTestOnBorrow(true);
config.setMaxTotal(10);
connectionPool = new GenericObjectPool<>(pcf, config);
pcf.setPool(connectionPool);
return new PoolingDataSource<>(connectionPool);
}
private GenericObjectPool<PoolableConnection> getConnectionPool() {
return connectionPool;
}
public static void main(String[] args) throws Exception {
ConnectionPoolExample demo = new ConnectionPoolExample();
DataSource dataSource = demo.setUp();
demo.printStatus();
try (Connection conn = dataSource.getConnection();
PreparedStatement stmt = conn.prepareStatement("SELECT * FROM authors")) {
demo.printStatus();
ResultSet rs = stmt.executeQuery();
while (rs.next()) {
System.out.println("Name: " + rs.getString("name"));
}
}
demo.printStatus();
}
/**
* Prints connection pool status.
*/
private void printStatus() {
System.out.println("Max : " + getConnectionPool().getNumActive() + "; " +
"Active: " + getConnectionPool().getNumActive() + "; " +
"Idle : " + getConnectionPool().getNumIdle());
}
}该代码显示以下状态作为输出示例：
Max : 0; Active: 0; Idle : 0 Max : 1; Active: 1; Idle : 0 Name: Raoul-Gabriel Urma Name: Mario Fusco Name: Alan Mycroft Max : 0; Active: 0; Idle : 1
Maven依赖
<!-- https://search.maven.org/remotecontent?filepath=org/apache/commons/commons-dbcp2/2.6.0/commons-dbcp2-2.6.0.jar -->
<dependency>
<groupId>org.apache.commons</groupId>
<artifactId>commons-dbcp2</artifactId>
<version>2.6.0</version>
</dependency>
<!-- https://search.maven.org/remotecontent?filepath=org/apache/commons/commons-pool2/2.6.2/commons-pool2-2.6.2.jar -->
<dependency>
<groupId>org.apache.commons</groupId>
<artifactId>commons-pool2</artifactId>
<version>2.6.2</version>
</dependency>
<!-- https://search.maven.org/remotecontent?filepath=mysql/mysql-connector-java/8.0.17/mysql-connector-java-8.0.17.jar -->
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>8.0.17</version>
</dependency>