具体问题求解（在线等）

Question

try {
            Context ctx = new InitialContext();
            javax.sql.DataSource ds = (javax.sql.DataSource)ctx.lookup("jdbc/book");
            Connection conn = ds.getConnection();
            Statement cs=conn.createStatement("SELECT * FROM books");
ResultSet rs=cs.executeQuery();
while(rs.next())
{
out.println(rs.getString("字段名"));
}
        } catch (Exception e) {
            e.printStackTrace();
        }