jdbc链接数据库学习记录

╰半橙微兮° 2022-06-09 00:19 235阅读 0赞

就直接代码上路：

public class DBUtils {
        private static Properties props = new Properties();
        private static ThreadLocal<Connection> connectionHolders = new ThreadLocal<Connection>();
        static {
            InputStream ips = DBUtils.class.getClassLoader().getResourceAsStream("com/gmai/verre/utils/db.properties");
            //采用classloader的方式主要是通过他的getResourceAsStream方法去获取配置文件
            try {
                props.load(ips);//加载文档
            } catch (IOException e) {
                e.printStackTrace();
                throw new RuntimeException("Deloading the property file is fail");
            }
        }
        public synchronized static Connection getConnection() {
       //创建获取数据库对象，返回单一的连接对象
            Connection conn= connectionHolders.get() ;
            if (conn ==null ) {
                conn =getConn();
                connectionHolders.set(conn);
            }
            return conn;
        }
        public static Connection getConn() {
       // 获取数据库连接,返回连接结果
            Connection conn = null;
            try {
                Class.forName(props.getProperty("driveName"));
                conn = DriverManager.getConnection(props.getProperty("url"), props.getProperty("username"),
                        props.getProperty("pwd"));
            } catch (ClassNotFoundException e) {
                e.printStackTrace();
            } catch (SQLException e) {
                e.printStackTrace();
                throw new RuntimeException("The remote access connection failed");
            }
            return conn;
        }
        public static void close() {
            Connection conn = connectionHolders.get();
            if (conn != null) {
                try {
                    conn.close();
                    connectionHolders.set(null);
                } catch (SQLException e) {
                    e.printStackTrace();
                    throw new RuntimeException("Close the connection to the database is failed.");
                }
            }
        }
        public static PreparedStatement prepare(Connection conn, String sql) {
            PreparedStatement ps=null;
            try {
                ps = conn.prepareStatement(sql);
            } catch (SQLException e) {
                e.printStackTrace();
            }
            return ps;
        }
        public static void close(PreparedStatement ps) {
            try {
            if(ps!=null) {
                ps.close();
                ps=null;
                }
            }catch (SQLException e) {
                e.printStackTrace();
            }
        }
    }