第二个sql语句得到的resultset对象是空的，什么原因？

public ListgetAll1(String name) throws Exception {

 Listresult = new ArrayList();

 Connection con = DatabaseConnection.getConnection();

 String na=null;

 String sql1= "select * from guanzhu where guanzhu=?";

 PreparedStatement ps1 = con.prepareStatement(sql1);

 ps1.setString(1, name);

 ResultSet rs1 = ps1.executeQuery();

 while(rs1.next()){

 Connection con1 = DatabaseConnection.getConnection();

 na=rs1.getString("beiguanzhu");

 String sql = "select * from message where author=? order by modified desc"; PreparedStatement ps = con1.prepareStatement(sql);

 ps.setString(1, na); ResultSet rs = ps.executeQuery();

 while (rs.next()) {

 Message m = new Message();

 m.setId(rs.getInt("id"));

 m.setTitle(rs.getString("title"));

 m.setContent(rs.getString("content"));

 m.setModified(rs.getDate("modified"));

 m.setAuthor(rs.getString("author"));

 result.add(m);

 System.out.println(rs.getString("author")+"");

 }

 }

 return result;
 }