我想使用servlet中的集合从数据库中获取数据

Question

protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
        response.getWriter().append("Served at: ").append(request.getContextPath());

viewService vs= new viewService();

    ArrayList<BeanClass> al = null;
    try {
        al = vs.view(request, response);
    } catch (ClassNotFoundException | SQLException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }       
    for(BeanClass s : al)
    {
        System.out.println(s.getUsername() + " | "+ s.getPassword() + " | "+s.getAge()+"|"+s.getEmail());
    }
}

另一个班级

public class viewService {

public ArrayList<BeanClass> view(HttpServletRequest request,
        HttpServletResponse response) throws SQLException, ClassNotFoundException, IOException
{   
    PrintWriter out = response.getWriter();
    HttpSession session = request.getSession(false);

if (session != null) {
    String username = (String) session.getAttribute("name");
    out.print("Hello, " + username + " Welcome to Profile");


    ArrayList<BeanClass> al = new ArrayList<BeanClass>();

    Class.forName("com.mysql.jdbc.Driver");
    Connection conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/servlet","root","root");
    Statement st =  conn.createStatement();

    ResultSet rs = st.executeQuery("select * from registration where Username = name");

    while(rs.next())
    {
        BeanClass bbc= new BeanClass();

        bbc.setUsername(rs.getString(1));
        bbc.setPassword(rs.getString(2));
        bbc.setAge(rs.getString(3));
        bbc.setEmail(rs.getString(4));

        al.add(bbc);

    }

    return al;

}
else{out.print("please login first");}
return null;
}}