自定义连接池

import java.sql.Array;
import java.sql.Blob;
import java.sql.CallableStatement;
import java.sql.Clob;
import java.sql.Connection;
import java.sql.DatabaseMetaData;
import java.sql.NClob;
import java.sql.PreparedStatement;
import java.sql.SQLClientInfoException;
import java.sql.SQLException;
import java.sql.SQLWarning;
import java.sql.SQLXML;
import java.sql.Savepoint;
import java.sql.Statement;
import java.sql.Struct;
import java.util.LinkedList;
import java.util.Map;
import java.util.Properties;
import java.util.concurrent.Executor;

public class MyConnection implements Connection{
	private LinkedList pool;//创建连接池
	private Connection cn;//是一个没有增强的原对象
	public MyConnection(LinkedList pool,Connection cn) {
		this.pool = pool;
		this.cn = cn;
	}
	//增强close方法,实现调用该方法，不是关闭connection对象，而是归还到池子中
	@Override
	public void close() throws SQLException {
		this.pool.add(this);
	}
	
	@Override
	public Statement createStatement() throws SQLException {
		Statement st = this.cn.createStatement();
		return st;
	}

    //....实现Connection接口的所有方法,省略...只重写了close()方法和createStatement()方法


}

import java.io.PrintWriter;
import java.sql.Connection;
import java.sql.SQLException;
import java.sql.SQLFeatureNotSupportedException;
import java.util.LinkedList;
import java.util.logging.Logger;
import javax.sql.DataSource;
import day03.JDBCUtil;

public class MyDataSource implements DataSource{
	private LinkedList pool = new LinkedList<>();
	public MyDataSource() {
		for (int i = 0; i < 5; i++) {
			//创建五个MyConnection，塞入到池子中
			MyConnection cn = new MyConnection(pool, JDBCUtil.getConnection());
			pool.add(cn);
		}
	}
	@Override
	public Connection getConnection() throws SQLException {
		if (pool.size()==0) {
			for (int i = 0; i < 5; i++) {
				//就在创建五个MyConnection，塞入到池子中
				MyConnection cn = new MyConnection(pool, JDBCUtil.getConnection());
				pool.add(cn);
			}
		}
		Connection cn = pool.remove();
		return cn;
	}
    //实现DataSource接口 实现所有方法,只重写了getConnection()方法,其他方法在此省略...
}