Question

我有5个班级。

访问仪表板。
一组要进行故障排除的功能。
查看学生名单。
添加学生。
学生对象

访问studentController时，表中包含信息。我正在将数据添加到另一个表中的表中，并且继续保存该表，但是它不会更新该表

学生班

package sample;

public class Student {

    String name;
    String amail;

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getAmail() {
        return amail;
    }

    public void setAmail(String amail) {
        this.amail = amail;
    }

    public Student(String name, String amail) {
        this.name = name;
        this.amail = amail;
    }
}

DBConnection类

package sample;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;


public class DBConnection {
    public Connection connection;
    String dbname="student";
    String username="root";
    String password="";

    public java.sql.Connection getConnection(){
        try {
            Class.forName("com.mysql.jdbc.Driver");
            connection= DriverManager.getConnection("jdbc:mysql://localhost/"+dbname,username,password );
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return  connection;
    }
}

DBFunc类

package sample;
import javafx.collections.FXCollections;
import javafx.collections.ObservableList;
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
public class DBfunc {
    public  void insertbolim(String name,String amail) throws SQLException {
        DBConnection dbConnection= new DBConnection();
        Connection connection=dbConnection.getConnection();
        String sql="INSERT INTO student (name,amail) VALUES ('"+name+"','"+amail+"')";
        Statement statement= null;
        try {
            statement = connection.createStatement();
        } catch (SQLException e) {
            e.printStackTrace();
        }
        statement.executeUpdate(sql);
    }
   public ObservableList selectbolim() throws SQLException {
        ObservableList<Student> nomi=FXCollections.observableArrayList();
        DBConnection db =new DBConnection();
        Connection connection =db.getConnection();
        Statement statement =connection.createStatement();
        String sql="SELECT * FROM `student`";
        ResultSet rs=statement.executeQuery(sql);
        while(rs.next())
        {
            nomi.add(new Student(rs.getString(2),rs.getString(3)));
        }
        return nomi;
    }
}

ControllerStudents类

package sample;
import javafx.event.ActionEvent;
import javafx.fxml.FXML;
import javafx.fxml.FXMLLoader;
import javafx.scene.Scene;
import javafx.scene.control.TableColumn;
import javafx.scene.control.TableView;
import javafx.scene.control.cell.PropertyValueFactory;
import javafx.scene.layout.AnchorPane;
import javafx.stage.Stage;
import java.io.IOException;
import java.net.URL;
import java.sql.SQLException;
import java.util.ResourceBundle;
public class ControllerStudents implements  Runnable{
    @FXML
    private TableColumn<Student, String> colname;
    @FXML
    private TableColumn<Student, String> colamail;
    @FXML
    private TableView<Student> tbview;
    @FXML
    void initialize() {
         Refresh();
    }
    @Override
    public void run() {
        Refresh();
    }
    public  void Refresh(){
        DBfunc dBfunc = new DBfunc();
        colname.setCellValueFactory(new PropertyValueFactory<Student,String>("name"));
        colamail.setCellValueFactory(new PropertyValueFactory<Student,String>("amail"));
        try {
            tbview.setItems(dBfunc.selectbolim());
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
    @FXML
    void addstudentaction(ActionEvent event) {
        AnchorPane pane = null;
        try {
            pane = FXMLLoader.load(getClass().getResource("../sample/AddStudents.fxml"));
        } catch (IOException e) {
            e.printStackTrace();
        }
        Stage stage =new Stage();
        stage.setTitle("Add Students");
        stage.setResizable(false);
        stage.setMaximized(false);
        stage.setScene(new Scene(pane));
        stage.show();
    }
}

AddStudent类

package sample;

import javafx.event.ActionEvent;
import javafx.fxml.FXML;
import javafx.scene.control.TextField;

import java.sql.SQLException;

public class AddStudents {

    @FXML
    private TextField txtname;

    @FXML
    private TextField txtamail;

    @FXML
    void saveaction(ActionEvent event) {

DBfunc dBfunc = new DBfunc();
        try {
            dBfunc.insertbolim(txtname.getText(),txtamail.getText());
        } catch (SQLException e) {
            e.printStackTrace();
        }
        ControllerStudents cs=new ControllerStudents();
        Thread thread = new Thread(cs);
        thread.start();
    }}

Exception in thread "Thread-4" java.lang.NullPointerException
    at sample.ControllerStudents.Refresh(ControllerStudents.java:52)
    at sample.ControllerStudents.run(ControllerStudents.java:45)
    at java.lang.Thread.run(Thread.java:748)

使用SQL查询从另一个类更新表

0 个答案: