JDBC自动生成主键值

  @Test
    public void test3(){
        Connection conn = null;
        PreparedStatement preparedStatement = null;
        ResultSet resultSet = null;
        String sql = "insert into student(name,password) values(?,?)";

        try {
            conn = Methods.getConnection();

            //使用重载的prepareStatement(sql,flag)来生成prepareStatement对象
            preparedStatement = conn.prepareStatement(sql,Statement.RETURN_GENERATED_KEYS);

            preparedStatement.setString(1,"yang5");
            preparedStatement.setString(2,"1235");

            preparedStatement.executeUpdate();

            //通过getGenerateKeys获取包含了新生成主键的ResultSet对象
            //在ResultSet中只有一列GENERATED_KEY,用于存放新生成的主键值。
            resultSet = preparedStatement.getGeneratedKeys();
            if(resultSet.next()){
                System.out.println(resultSet.getObject(1));
            }
            ResultSetMetaData rsmd = resultSet.getMetaData();
            for (int i = 0; i < rsmd.getColumnCount(); i++) {
                System.out.println(rsmd.getCatalogName(i+1));
            }

        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            Methods.release(preparedStatement,conn,resultSet);
        }