Servlet无法连接到数据库/无法检索数据

Question

由于某种原因，我无法将项目检索/提交到本地数据库中。提交信息后，包含Servlet的下一页为空白。我确实有一个测试类来测试数据库的连接，并且它能够成功找到数据库中的项目/将项目提交到数据库中。

我不太清楚问题可能是什么，可能是到我的数据库或sql的连接。寻找任何可能的帮助-谢谢！

同样，您会看到，玻璃鱼说在搜索用户之前，“ Here1”之后出现了第一个问题。

下面是登录控制器的代码：

    package Servlets;

 import java.io.IOException;

     import java.sql.SQLException;

     import java.util.logging.Level;

     import java.util.logging.Logger;

     import javax.servlet.ServletException;

     import javax.servlet.http.HttpServlet;

     import javax.servlet.http.HttpServletRequest;

     import javax.servlet.http.HttpServletResponse;

     import javax.servlet.http.HttpSession;

     import java.sql.Timestamp;

     import beans.*;

     import dao.*;

     public class LoginController extends HttpServlet {




         @Override   

     protected void doPost(HttpServletRequest request, HttpServletResponse response)   throws ServletException, IOException {       



             HttpSession session = request.getSession();
             Validator valid = new Validator();
             String email = request.getParameter("email");
             String password = request.getParameter("password");
            // Date date = new Date();
             long millis=System.currentTimeMillis();  
             java.sql.Date date=new java.sql.Date(millis);  
             java.sql.Time time=new java.sql.Time(millis);  
             DBManager manager = (DBManager) session.getAttribute("manager");

             User user = null;       
             if (!valid.validatePassword(password)){
                 session.setAttribute("passErr", "Error: password format incorrect");
                 request.getRequestDispatcher("login.jsp").include(request, response);
             }
             else{
                     try {  
                         System.out.println("Here1");
                        user = manager.findUser(email, password);
                        int logid = manager.logCount()+1;
                        System.out.println("Here2");
                        if (user!=null){
                            if(user.getAccounttype().equals("Staff")){
                                session.setAttribute("staff", "True");

                            }
                            System.out.println("Here3");
                            session.setAttribute("loggedin", "True");
                            session.setAttribute("logid", logid);
                            session.setAttribute("user", user);
                            manager.loginTimestamp(logid, user.getID(), date.toString(), time.toString());
                            request.getRequestDispatcher("welcome.jsp").include(request, response);
                            System.out.println("Here4");
                        }
                        else{
                            System.out.println("Here5");
                            session.setAttribute("existErr", "User does not exist");
                            request.getRequestDispatcher("login.jsp").include(request, response);
                        }

                     } catch (SQLException | NullPointerException ex) {           

                           System.out.println(ex.getMessage()==null ? "User does not exist" : "welcome");  

                     }

             } 

      }
     }

还有我用于数据库管理器的其他代码是：

    public class DBManager {

private Statement st;

public DBManager(Connection conn) throws SQLException {       
   st = conn.createStatement();   
}

//Find user by email and password in the database   
public User findUser(String email, String password) throws SQLException {    
   String fetch = "select * from ISDUSER.USERS where EMAIL = '" + email + "' and PASSWORD='" + password + "'";
   ResultSet rs = st.executeQuery(fetch);
   while(rs.next()){
       String useremail = rs.getString(3);
       String pass = rs.getString(4);
       if (useremail.equals(email) && pass.equals(password)){
            int id = rs.getInt(1);
            String name = rs.getString(2);
            String address = rs.getString(5);
            String type = rs.getString(7);
            System.out.println("here + " + type);
            boolean isRegistered = rs.getBoolean(6);
            return new User(id, name, email, pass, address, isRegistered, type);

        } 
   }
   return null;   
}

Answer 1

您必须找出连接数据库的方法。您必须提供数据库的IP，端口，用户名，密码。如果没有，如何连接？我认为互联网上有很多资源可以帮助您解决此问题