java - 将 boolean 值设置为 Activity 或非 Activity 存在于包含用户列表的 View 页面的下拉菜单中

Question

我是编程初学者，这是我的 DAO 文件，用于一个带有更新和删除方法的简单登录应用程序，更新和删除方法都有单独的 servlet 文件，我可以毫无问题地执行相同的操作，有人问我向表中添加一个 boolean 列，其中 true 值指示用户 处于 Activity 状态，反之亦然。

我知道引用 boolean 功能的代码是错误的。我希望我能得到一些帮助。 boolean 值的访问器方法写入另一个文件中。我在整个互联网甚至这个网站上进行了搜索，但两天来还是无法弄清楚。

import java.util.*;
import java.sql.*;

public class UserDao {

//connection to jdbc mysql server//

public static Connection getConnection(){
    Connection conn=null;
    String url="jdbc:mysql://localhost:3306/";
    String dbName="mylogin";
    String driver="com.mysql.jdbc.Driver";
    String userName="root";
    String dbPassword="admin";
       try{  
            Class.forName(driver);  
            conn=DriverManager.getConnection(url + dbName,userName,dbPassword);  
        }catch(Exception e){
            System.out.println(e);
            }  
        return conn;  
    }  

   //* block to update the user details present inside a table in DB *//

   public static int update(User e){  
        int status=0;  
        try{  
            Connection conn=UserDao.getConnection();  
            PreparedStatement ps=conn.prepareStatement("UPDATE UDATA SET username=?,password=?,address=?,phone=?,email=? where id=?");  
            System.out.println("UPDATE UDATA SET username="+e.getName()+",password="+e.getPassword()+",address="+e.getAddress()+",phone="+e.getPhone()+",email="+e.getEmail()+" where id="+e.getId());

            ps.setString(1,e.getName());  
            ps.setString(2,e.getPassword());  
            ps.setString(3,e.getAddress());  
            ps.setString(4,e.getPhone());  
            ps.setString(5,e.getEmail());
            ps.setInt(6,e.getId());  

            status=ps.executeUpdate();  

            conn.close();  
        }catch(Exception ex){ex.printStackTrace();}  

        return status;  
    }  

    // code for performing deletion process//

     public static int delete(int id){  
            int status=0;  
            try{  
                Connection conn=UserDao.getConnection();  
                PreparedStatement ps=conn.prepareStatement("DELETE FROM udata where id=?");  
                ps.setInt(1,id);  
                status=ps.executeUpdate();  

                conn.close();  
            }catch(Exception e){e.printStackTrace();}  

            return status;  
        }  

   //code to perform the boolean operation //

   public static boolean userStatus(){
         int id=0;
         int status=0;
         boolean active=true;
         try{
                Connection conn=UserDao.getConnection();  
                PreparedStatement ps=conn.prepareStatement("SELECT CASE WHEN status IS NULL THEN 'false' ELSE 'true' END FROM udata;");
                PreparedStatement ps1=conn.prepareStatement("UPDATE udata where id=? and status=?"); 
                ps.setBoolean(1, active);
                ps.setInt(2, id);
                status=ps.executeUpdate();

        }

        return active;
     }

Here is the setter and getter methods of the parameters. There is a similar file for Users This one only involves Admin credentials

     public class Admin {

private int id;  
private String adName,adPassword;  
private static boolean userStatus;
public int getId() {  
    return id;  
}  
public void setId(int id) {  
    this.id = id;  
}  
public String getName() {  
    return adName;  
}  
public void setName(String name) {  
    this.adName = name;  
}  
public String getPassword() {  
    return adPassword;  
}  
public void setPassword(String password) {  
    this.adPassword = password;  
}  
public static boolean isUserStatus(){
    return userStatus; 
    }
public void setUserStatus(boolean active){
    Admin.userStatus=true;
}
}

Answer 1

查看代码，您在 userStatus() 方法中似乎在错误的准备好的语句中设置了参数

改变

ps.setBoolean(1, active);
ps.setInt(2, id);

到

ps1.setBoolean(1, active);
ps1.setInt(2, id);

但我仍然很困惑为什么要为选择查询设置参数？另外为什么你不执行它来获取结果集？