Class.forName(driver);// mysql 數(shù)據庫：“com.mysql.jdbc.Driver”

Connection conn=DriverManager.getConnection(url,userName,password);

Statement statement =conn.createStatement();

ResultSet rs =statement.executeQuery(sql);

private static final String URL = "jdbc:mysql://127.0.0.1:3306/java16_order_system?characterEncoding=utf8&useSSL=true";

package model;
 
import com.mysql.jdbc.jdbc2.optional.MysqlDataSource;
 
import javax.sql.DataSource;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
 
// DBUtil 本質上是一個管理了單例的 DataSource 的類
public class DBUtil {
    private static final String URL = "jdbc:mysql://127.0.0.1:3306/java16_order_system?characterEncoding=utf8&useSSL=true";
//    private static final String URL = "jdbc:mysql://47.98.116.42:3306/java16_order_system?characterEncoding=utf8&useSSL=true";
    private static final String USERNAME = "root";
    private static final String PASSWORD = "rota";
 
    private static volatile DataSource dataSource = null;
 
    public static DataSource getDataSource() {
        if (dataSource == null) {
            synchronized (DBUtil.class) {
                if (dataSource == null) {
                    dataSource = new MysqlDataSource();
                    ((MysqlDataSource)dataSource).setURL(URL);
                    ((MysqlDataSource)dataSource).setUser(USERNAME);
                    ((MysqlDataSource)dataSource).setPassword(PASSWORD);
                }
            }
        }
        return dataSource;
    }
 
    // 數(shù)據庫連接失敗是很常見的問題. 如果失敗, 后續(xù)的操作肯定也是失敗的.
    // 如果發(fā)現(xiàn) Connect 為 null, 就說明數(shù)據庫連接失敗, 就需要查看錯誤信息(Tomcat 的日志)
    // 常見的問題就是, url, username, password 等信息寫錯了, 或者數(shù)據庫沒有啟動.
    public static Connection getConnection() {
        try {
            return getDataSource().getConnection();
        } catch (SQLException e) {
            e.printStackTrace();
        }
        System.out.println("數(shù)據庫連接失敗, 請檢查數(shù)據庫是否啟動正確, url 是否正確");
        return null;
    }
 
    public static void close(Connection connection, PreparedStatement statement, ResultSet resultSet) {
        try {
            if (resultSet != null) {
                resultSet.close();
            }
            if (statement != null) {
                statement.close();
            }
            if (connection != null) {
                connection.close();
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
 
 
}