/*** 获取数据库链接的静态方法  这样子就保证了只加载一次文件的操作* @return* @throws Exception*/public static Connection getConn() throws Exception{String jdbcDriver=null;String url=null;String user=null;String password=null;Properties p=new Properties();InputStream is=JDBCTools.class.getClassLoader().getResourceAsStream("jdbc.properties");p.load(is);jdbcDriver=p.getProperty("jdbcDriver");url=p.getProperty("url");user=p.getProperty("user");password=p.getProperty("password");Class.forName(jdbcDriver);return DriverManager.getConnection(url, user, password);}

        /*** 关闭从数据库服务器等索取的资源:先关闭后获取的* @param conn* @param pstmt*/public static void closeResource(Connection conn,Statement stmt,ResultSet rs){if (rs != null) {try {rs.close();} catch (SQLException e) {e.printStackTrace();}}if (stmt != null) {try {stmt.close();} catch (SQLException e) {e.printStackTrace();}}if (conn != null) {try {conn.close();} catch (SQLException e) {e.printStackTrace();}}

        /*** 统一的更新操作 Statement:insert update delete* @param conn* @param sql* @throws Exception*/public void update(String sql){Connection conn=null;Statement stmt=null;try {conn=JDBCTools.getConn();stmt=conn.createStatement();stmt.executeUpdate(sql);} catch (Exception e) {e.printStackTrace();} finally{closeResource(conn, stmt, null);}}/*** 适用于PreparedStatment* @param sql* @param args*/public void update2(String sql,Object ... args){Connection conn=null;PreparedStatement pstmt=null;ResultSet rs=null;try {conn=JDBCTools.getConn();pstmt=conn.prepareStatement(sql);for(int i=0;i<args.length;i++){pstmt.setObject(i+1, args[i]);}pstmt.executeUpdate();} catch (Exception e) {e.printStackTrace();} finally{JDBCTools.closeResource(conn, pstmt, rs);}}

        /*** 泛型方法  反射机制  通用的查询方法存储实体* @param clazz* @param sql* @param args* @return*/public <T> T getT(Class<T> clazz,String sql,Object ... args){T t=null;Connection conn=null;PreparedStatement pstmt=null;ResultSet rs=null;ResultSetMetaData rsmd=null;try {conn=JDBCTools.getConn();pstmt=conn.prepareStatement(sql);for(int i=0;i<args.length;i++){pstmt.setObject(i+1, args[i]);}rs=pstmt.executeQuery();if (rs.next()) {t=clazz.newInstance();Map<String, Object> map=new HashMap<String, Object>();//解析sql获取对象rsmd = rs.getMetaData();int numberOfColumns = rsmd.getColumnCount();for(int i=0;i<numberOfColumns;i++){　　　　　　　　　　　　　　　　　　　　　　　　//获取列的名字，如果有别名，则获取的是别名String columnName=rsmd.getColumnLabel(i+1);  map.put(columnName, rs.getObject(columnName));}if (map.size() > 0) {for(Map.Entry<String, Object> entry: map.entrySet()){String columnName=entry.getKey();Object columnValue=entry.getValue();Field field = t.getClass().getDeclaredField(columnName);field.setAccessible(true);field.set(t, columnValue);}}}} catch (Exception e) {e.printStackTrace();} finally{JDBCTools.closeResource(conn, pstmt, rs);}return t;}