程式碼如下：

package henu.utils;
import java.sql.*;
public class DbUtil {
	/**
	 * 宣告連線資料庫的資訊，例如資料庫URL、使用者名稱、密碼等
	 */
	
	private static String url = "jdbc:mysql://localhost:3306/user";
	private static String user = "root";
	private static String password = "123";
	
	/**
	 * 宣告相關物件
	 */
	private static Statement stmt = null;
	private static ResultSet rs = null;
	private static Connection conn = null;
	
	/**
	 * 建立資料庫連結
	 */
	
	public static synchronized Connection getConnect() {
		try {
			//載入驅動
			Class.forName("com.mysql.jdbc.Driver");
			conn = DriverManager.getConnection(url, user, password);
		} catch (Exception e) {
			e.printStackTrace();
		}
		return conn;
	}
	
	
	/**
	 * 執行insert、update、delete語句
	 * 
	 * 返回int型別
	 */
	
	public static int executeUpdate(String sql) {
		int result = 0;
		
		try {
			stmt = getConnect().createStatement();
			result = stmt.executeUpdate(sql);
			
		} catch (SQLException e) {
			
			e.printStackTrace();
		}
		return result;
	}
	/**
	 * 執行select語句
	 * 
	 * 返回查詢ResultSet的結果集
	 */
	public static ResultSet executeQuery(String sql) {
		
		try {
			stmt = getConnect().createStatement();
			rs = stmt.executeQuery(sql);
		} catch (SQLException e) {
			e.printStackTrace();
		}
		return rs;
	}
	
	/**
	 * 執行動態的Sql語句
	 * @param sql含有引數的動態Sql語句
	 * @result 返回PreparedStatement物件
	 */
	
	public static PreparedStatement executePrepareStatement(String sql) {
		PreparedStatement ps = null;
		try {
			ps = getConnect().prepareStatement(sql);
			
		} catch (Exception e) {
			
			e.printStackTrace();
		}
		
		return ps;
	}
	
	/**
	 * 事務回滾
	 */
	
	public static void rollback() {
		try {
			getConnect().rollback();
		} catch (SQLException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
	}
	
	/**
	 * 關閉資料庫
	 */
	
	public static void close() {
		
			try {
				if(rs!=null)
					rs.close();
				if(stmt!=null)
					rs.close();
				if(conn!=null)
					conn.close();
				
			} catch (SQLException e) {
				e.printStackTrace();
			}
	}
	
	/**
	 * 連線Sql Server 2008
	 * 需要下載sqljdbc.jar
	 * Class.forName("com.microsoft.jdbc.sqlserver.SQLServerDriver");
	 * url = "jdbc:sqlserver://localhost:1433;DatabaseName = dbName"
	 * 
	 * 
	 * 連線Oracle資料庫
	 * 載入驅動程式
	 * DriverManager.registerDriver(new oracle.jdbc.driver.OracleDriver());
	 * url = "jdbc:oracle:oci8:@user"
	 *或者
	 *Class.forName("oracle.jdbc.driver.OracleDriver").newInstance();
	 *url = "jdbc:oracle:thin:@localhost:1512:user" 
	 */
	
}
 

3、資料庫連線池：在一個虛擬的池中預先建好一定數量的Connection物件等待客戶端的連線，當客戶端連線時則分配一個空閒的Connection物件給客戶端連線資料庫；當這個客戶端請求結束時則將Connection物件歸還給池中，用來等待下一個客戶端的訪問。獨立於Web伺服器的資料庫連線池：dbcp方式

需要commons-dbcp-xxx.jar和commons-pool-xxx.jar

package henu.util;

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

import javax.sql.DataSource;

import org.apache.commons.dbcp.BasicDataSource;
import org.apache.commons.dbcp.BasicDataSourceFactory;
/**
 * DBCP
 * @suqichang
 * 2017-10-20
 */
public class DbUtil {
	
	private static BasicDataSource dataSource = null;

	public static void init(){
		if (dataSource != null){
			try{
				dataSource.close();
			}catch(Exception e){
				e.printStackTrace();
			}
			dataSource = null;
		}
		
		try {
			Properties p = new Properties();
			//硬編碼方式
			p.setProperty("driverClassName", "com.mysql.jdbc.Driver");
			p.setProperty("url", "jdbc:mysql://localhost:3306/webdisk");
			p.setProperty("username", "root");
			p.setProperty("password", "123456");
			p.setProperty("maxActive", "30");
			p.setProperty("maxIdle", "10");
			//讀取配置檔案
			//p.load(DbUtil.class.getClass().getResourceAsStream("/db.properties"));
			dataSource = (BasicDataSource)BasicDataSourceFactory.createDataSource(p);
		} catch(Exception e) {
			e.printStackTrace();
		}
	}
	
	public static DataSource getDataSource()
	{
		if(dataSource == null) {
			init();
		}
		return dataSource;
	}
	
	public static synchronized Connection getConnection() {
		Connection con = null;
		if(dataSource == null) {
			init();
		}
		if(dataSource!=null) {
			try {
				con = dataSource.getConnection();
			} catch (SQLException e) {
				e.printStackTrace();
			}
		}
		return con;
	}
}