java 数据库缓冲池 使用c3p0

比较爽的一点就是
当Connection归还缓冲池时，c3p0会很小心的关闭
这条连接打开的Statement和ResultSet,免去了使用时
自己动手小心翼翼的关闭。

c3p0使用非常简单，这里给一个例子

package common.db;

import java.sql.Connection;
import java.sql.SQLException;
import java.util.Properties;


import com.mchange.v2.c3p0.ComboPooledDataSource;
import com.mchange.v2.c3p0.DataSources;

public final class ConnectionManager {
private static ConnectionManager instance;

public ComboPooledDataSource ds;
private static String c3p0Properties="c3p0.properties";

private ConnectionManager() throws Exception {
Properties p = new Properties();
p.load(this.getClass().getResourceAsStream(c3p0Properties));
ds = new ComboPooledDataSource();
}

public static final ConnectionManager getInstance() {
if (instance == null) {
try {
instance = new ConnectionManager();
} catch (Exception e) {
e.printStackTrace();
}
}
return instance;
}

public synchronized final Connection getConnection() {
try {
return ds.getConnection();
} catch (SQLException e) {
e.printStackTrace();
}
return null;
}

protected void finalize() throws Throwable {
DataSources.destroy(ds); //关闭datasource
super.finalize();
}

}

然后在ConnectionManager类的目录下再创建一个配置文件c3p0.properties
内容如下：
#db login parameters
driverClass=com.mysql.jdbc.Driver
jdbcUrl=jdbc:mysql://localhost/test?useUnicode=no&characterEncoding=GBK
user=test
password=test

#pool parameters
initialPoolSize=2
maxPoolSize=5
#maxIdleTime=10
#idleConnectionTestPeriod=5
autoCommitOnClose=true

完整的配置文件参数参看c3p0的文档

使用connection时很简单
Connection conn = ConnectionManager.getInstance().getConnection();
...
最后 conn.close() 即可