Java/JDBC/Swing - 检索下一条记录的问题

Question

我在检索 SQLite 数据库中的下一条记录时遇到了一些问题。我尝试创建了一个新的 ArrayList 和一个 Employee 的实例（一个带有 getter/setter 的类），但是我仍然有问题。我在网上搜索了最后一天半试图解决这个问题。我试过使用if(rs.next)/while(rs.next) 但是，只有while 似乎有效。我在网上看了几个教程，但遇到了SQLITE TYPE_FORWARD_ONLY.我已经实现的问题：

ResultSet.TYPE_SCROLL_SENSITIVE, 
ResultSet.CONCUR_UPDATABLE

但仍然没有运气，所以我决定添加一个迭代器/计数器，因为我的 SQLite 数据库中的 ID 是唯一的。但是，问题似乎是迭代器/计数器没有增加，但是，如果我手动设置值，即 2，我会在数据库中获得第二条记录，依此类推。

nextEmployee.addActionListener(new ActionListener() {

        @Override
        public void actionPerformed(ActionEvent e) {

            // TODO Auto-generated method stub
            Connection connection = null;
            PreparedStatement pst = null;
            Statement statement = null;
            ResultSet rs = null;
            int i = 1;
            try {                   
                Class.forName("org.sqlite.JDBC");
                connection = DriverManager.getConnection("jdbc:sqlite:employeeDatabase.sqlite");
                connection.setAutoCommit(false);                        

                 String sql = "SELECT ID, Name, Gender, DOB, Address, Postcode, NIN, JobTitle, StartDate, Salary, Email from employees WHERE ID= " +(i);                                     

                pst = connection.prepareStatement(sql);
                rs = pst.executeQuery();    

                for (i = 1; i <= 4; i++){
                    while (rs.next()){

                        String  id = rs.getString(1);
                        String  name = rs.getString(2);
                        String  gender = rs.getString(3);
                        String  dob = rs.getString(4);
                        String  Address = rs.getString(5); 
                        String  Postcode = rs.getString(6);
                        String  NIN = rs.getString(7);
                        String  JobTitle = rs.getString(8);
                        String  StartDate = rs.getString(9);
                        String  Salary = rs.getString(10);
                        String  email = rs.getString(11);

                        idTextField.setText(id);
                        nameTextField.setText(name);
                        genderTextField.setText(gender);
                        dobTextField.setText(dob);

                        addressTextField.setText(Address);
                        postcodeTextField.setText(Postcode);
                        ninTextField.setText(NIN);
                        jobtitleTextField.setText(JobTitle);
                        startdateTextField.setText(StartDate);
                        salaryTextField.setText(Salary);
                        emailTextField.setText(email);


                        //   i++;
                        connection.commit();

                        JOptionPane.showMessageDialog(null, "Employee has been found");
                    }
                }                   

                rs.close();
                pst.close();
                connection.close();
            }


            catch ( Exception e1 ) {

                JOptionPane.showMessageDialog(null, "No more records exist");

            }
        }});

我的想法已经不多了。这是最后一块拼图，我已经成功实现了创建/插入、删除、搜索、更新。有人可以告诉我为什么这个迭代器/计数器不会增加吗？

谢谢。

编辑 -

员工类

public class Employee extends Person {
    private int id;
    private float salary;
    private String startDate;
    private String title;
    private String email;



    public int getid(){
        return id;
    }

    public void setid(int id){
        this.id = id;
    }

    public float getsalary(){
        return salary;
    }

    public void setsalary(float salary){
        this.salary = salary;
    }

    public String getstartDate(){
        return startDate;
    }

    public void setstartDate(String startDate){
        this.startDate = startDate;
    }

    public String gettitle(){
        return title;
    }

    public void settitle(String title){
        this.title = title;
    }

    public String getemail(){
        return email;
    }

    public void setemial(String email){
        this.email = email;
    }



    public Employee(){
        this("", 'N', "", new Date(), "", "", 0, 0, "", "", "");
    }

    public Employee( String Name, char Sex, String natIncsNumber, Date date, String address, String postcode, int ID, float Salary, String Startdate, String Title, String Email) {
        super(Name, Sex,natIncsNumber, date, address, postcode);
        this.id = ID;
        salary = 0.0f;
        this.startDate = Startdate;
        this.title = Title;
        this.email = Email;
    }


    public void setSalary(float salry){
        salary = salry;
    }

    public String toString(){
        return "Employee ID = " + id+ ", Employee Salary = " + salary + " Start Date = " + startDate + 
                " Title = " + title + " Email = " + email + super.toString();
    }


}

人物类-

import java.io.*;
public class Person implements Serializable{

    protected String name;
    protected char gender;
    protected String natIncsNo;
    protected Date dob;
    protected String Address;
    protected String Postcode;

    public String getName(){
        return name;
    }

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

    public char getGender(){
        return gender;
    }

    public void setGender(char gender){
        this.gender = gender;
    }

    public String getnatIncsNo(){
        return natIncsNo;
    }

    public void setnatIncsNo(String natIncsNo){
        this.natIncsNo = natIncsNo;
    }

    public Date getdob(){
        return dob;
    }

    public void setdob(Date dob){
        this.dob = dob;
    }

    public String getAddress(){
        return Address;
    }

    public void setAddress(String Address){
        this.Address = Address;
    }

    public String getPostcode(){
        return Postcode;
    }

    public void setPostcode(String Postcode){
        this.Postcode = Postcode;
    }


    public Person(String Name, char Sex, String natIncsNumber, Date date, String address, String postcode) {
        name = Name;
         gender = Sex;
         natIncsNo = natIncsNumber;
        dob = date;
        Address = address;
        Postcode = postcode;
    }


        public Person(){
            this("", 'N', "", new Date(), "", "");
        }

    public String toString(){



        String output = " Name: " + name + " Gender: " + gender +  " National Insurance Number: " + natIncsNo + 
                " Date Of Birth : " + dob + 
                 " Address: " + Address + " Postcode: " + Postcode;

        return output;

    }
    }

编辑 X 2-

EmployeeDAO 类

import java.security.spec.ECFieldF2m;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.ArrayList;

import javax.swing.JLabel;
import javax.swing.JOptionPane;

public class EmployeeDAO extends Employee {

    private Connection con;
    private Statement st;
    private ResultSet rs;

    public EmployeeDAO() { 



        Connection connection = null;
        try { 
            Class.forName("org.sqlite.JDBC");
            connection = DriverManager.getConnection("jdbc:sqlite:employeeDatabase.sqlite");
        } catch ( Exception e ) {
            System.err.println( e.getClass().getName() + ": " + e.getMessage() );
            System.exit(0);
        }
        System.out.println("Connection - database driver found");




        //insertEmployeeAtID(); 
        //selectAllEmployees();
        //insertEmployee();
        //deleteEmployeeByID();
    }





    public Statement getConnection() {
        return st;
    }

    public void closeConnection() throws SQLException { 
        if (con != null) con.close();
    }



    public ArrayList<Employee> selectAllEmployees(){
        Connection connection = null;
        Statement statement = null;
        try {
            Class.forName("org.sqlite.JDBC");
            connection = DriverManager.getConnection("jdbc:sqlite:employeeDatabase.sqlite");
            connection.setAutoCommit(false);
            System.out.println("Read operation - database successfully opened");

            statement = connection.createStatement();
            ResultSet resultset = statement.executeQuery( "SELECT * from employees" );
            while ( resultset.next() ) {
                int id = resultset.getInt("id");
                String  name = resultset.getString("name");
                String  email = resultset.getString("email");
                String  gender = resultset.getString("gender");
                String  dob = resultset.getString("dob");
                String  Address = resultset.getString("address"); 
                String  Postcode = resultset.getString("Postcode");
                String  NIN = resultset.getString("NIN");
                String  JobTitle = resultset.getString("JobTitle");
                String  StartDate = resultset.getString("StartDate");
                String  Salary = resultset.getString("Salary");


                System.out.println( "ID : " + id );
                System.out.println( "Name : " + name );
                System.out.println( "Gender : " + gender );
                System.out.println( "Date Of Birth : " + dob );
                System.out.println( "Address : " + Address );
                System.out.println( "Postcode : " + Postcode );
                System.out.println( "National Insurance Number : " + NIN );
                System.out.println( "Job Title : " + JobTitle );
                System.out.println( "Start Date : " + StartDate );
                System.out.println( "Salary : " + Salary );
                System.out.println( "Email: " + email );
                System.out.println();
            }
            resultset.close();
            statement.close();
            connection.close();
        } catch ( Exception e ) {
            System.err.println( e.getClass().getName() + ": " + e.getMessage() );
            System.exit(0);
        }
        System.out.println("Read operation successfully done"); 
        return new ArrayList<Employee>();

    }


    public String selectEmployeeByName() {
        Connection connection = null;
        Statement statement = null;
        try {
            Class.forName("org.sqlite.JDBC");
            connection = DriverManager.getConnection("jdbc:sqlite:employeeDatabase.sqlite");
            connection.setAutoCommit(false);
            System.out.println("Read operation - database successfully opened");

            statement = connection.createStatement();
            ResultSet resultset = statement.executeQuery( "SELECT * from employees WHERE Name = 'Brad Stones';" );
            while ( resultset.next() ) {
                int id = resultset.getInt("id");
                String  name = resultset.getString("name");
                String  email = resultset.getString("email");
                String  gender = resultset.getString("gender");
                String  dob = resultset.getString("dob");
                String  Address = resultset.getString("address"); 
                String  Postcode = resultset.getString("Postcode");
                String  NIN = resultset.getString("NIN");
                String  JobTitle = resultset.getString("JobTitle");
                String  StartDate = resultset.getString("StartDate");
                String  Salary = resultset.getString("Salary");

                /*
                System.out.println( "ID : " + id );
                System.out.println( "Name : " + name );
                System.out.println( "Gender : " + gender );
                System.out.println( "Date Of Birth : " + dob );
                System.out.println( "Address : " + Address );
                System.out.println( "Postcode : " + Postcode );
                System.out.println( "National Insurance Number : " + NIN );
                System.out.println( "Job Title : " + JobTitle );
                System.out.println( "Start Date : " + StartDate );
                System.out.println( "Salary : " + Salary );
                System.out.println( "Email: " + email );
                System.out.println();
                */
            }
            resultset.close();
            statement.close();
            connection.close();
        } catch ( Exception e ) {
            System.err.println( e.getClass().getName() + ": " + e.getMessage() );
            System.exit(0);
        }
        System.out.println("Read operation successfully done"); 
          return toString();
    }


    public boolean insertEmployee(){

        Connection connection = null;
        Statement statement = null;
        try {
            Class.forName("org.sqlite.JDBC");
            connection = DriverManager.getConnection("jdbc:sqlite:employeeDatabase.sqlite");
            connection.setAutoCommit(false);
            System.out.println("Insert operation -database successfully opened");
            statement = connection.createStatement();
            String sql =  "INSERT INTO employees (id, name, gender, NIN, dob, Address, Postcode,startDate, salary, email, JobTitle) "
                    + "VALUES ('1', 'Brad Stones', 'M', 'YU6593864T', '09-01-1987', '100 Dalton Road', 'M1 7TA', '09-01-1981','25000', 'BradSmith@mail.com', 'Tutor')";


            statement.executeUpdate(sql);
            statement.close();
            connection.commit();
            connection.close();
        } catch ( Exception e ) {
            System.err.println( e.getClass().getName() + ": " + e.getMessage() );
            System.exit(0);
        }
        System.out.println("Records successfully created");
        return false;
    }




    public boolean insertEmployeeAtID(){

        Connection connection = null;
        Statement statement = null;
        try {
          Class.forName("org.sqlite.JDBC");
          connection = DriverManager.getConnection("jdbc:sqlite:employeeDatabase.sqlite");
          connection.setAutoCommit(false);
          System.out.println("Update operation - database successfully opened");

          statement = connection.createStatement();
          String sql = "UPDATE employees set JobTitle = 'Potato' where ID=1;";
          statement.executeUpdate(sql);
          connection.commit(); 
          statement.close();
          connection.close();
        } catch ( Exception e ) {
          System.err.println( e.getClass().getName() + ": " + e.getMessage() );
          System.exit(0);
        }
        System.out.println("Update operation successfully done");
        return false;
      }




    public boolean deleteEmployeeByID(){

         Connection connection = null;
            Statement statement = null;
            try {
              Class.forName("org.sqlite.JDBC");
              connection = DriverManager.getConnection("jdbc:sqlite:employeeDatabase.sqlite");
              connection.setAutoCommit(false);
              System.out.println("Delete operation -database successfully opened");
              statement = connection.createStatement();
              String sql = "DELETE from employees where ID= 1";
              statement.executeUpdate(sql);
              connection.commit();
              statement.close();
              connection.close();
            } catch ( Exception e ) {
              System.err.println( e.getClass().getName() + ": " + e.getMessage() );
              System.exit(0);
            }
            System.out.println("Delete operation successfully done");
        return false;
    }

}

nextEmployee 方法-

List<Employee> list= empDAO.selectAllEmployees();

        int counter=0;
        nextEmployee.addActionListener(new ActionListener() {
            boolean isfirstTime = true;


            @Override
            public void actionPerformed(ActionEvent e) {
                if (isfirstTime) {
                    Connection connection = null;
                    PreparedStatement pst = null;
                    Statement statement = null;
                    ResultSet rs = null;
                    int i = 1;
                    try {

                        Class.forName("org.sqlite.JDBC");
                        connection = DriverManager.getConnection("jdbc:sqlite:employeeDatabase.sqlite");
                        connection.setAutoCommit(false);

                        String sql = "SELECT ID, Name, Gender, DOB, Address, Postcode, NIN, JobTitle, StartDate, Salary, Email from employees WHERE ID= "
                                + (i);

                        pst = connection.prepareStatement(sql);
                        rs = pst.executeQuery();

                        while(rs.next()){
                            EmployeeDAO empDao=new EmployeeDAO();
                            //set the variables for the employee


                            String id = rs.getString(1);
                            String name = rs.getString(2);
                            String gender = rs.getString(3);
                            String dob = rs.getString(4);
                            String Address = rs.getString(5);
                            String Postcode = rs.getString(6);
                            String NIN = rs.getString(7);
                            String JobTitle = rs.getString(8);
                            String StartDate = rs.getString(9);
                            String Salary = rs.getString(10);
                            String email = rs.getString(11);

                            idTextField.setText(id);
                            nameTextField.setText(name);
                            genderTextField.setText(gender);
                            dobTextField.setText(dob);

                            addressTextField.setText(Address);
                            postcodeTextField.setText(Postcode);
                            ninTextField.setText(NIN);
                            jobtitleTextField.setText(JobTitle);
                            startdateTextField.setText(StartDate);
                            salaryTextField.setText(Salary);
                            emailTextField.setText(email);

                            list.add(empDao);


                        }


                        rs.close();
                        pst.close();
                        connection.close();
                    }

                    catch (Exception e1) {

                        JOptionPane.showMessageDialog(null, "No more records exist");

                    }
                }else{
                    Employee emp=list.get(counter);
                    idTextField.setText(String.valueOf(emp.getid()));
                    //and so on. always get from emp
                    JOptionPane.showMessageDialog(null, "Employee has been found");


                }
            }
        });

Answer 1

您发布的代码对我来说太多了，我将向您发布一些我的代码，其中我创建了一个 dao 类以及我如何使用它。

道类：

public class SchnitzelDBDAO {

private static final Logger LOG = LoggerFactory.getLogger(SchnitzelDBDAO.class);
private Properties dbProperties;
private String action = "";
private Vector<Gericht> mealsActionPerformedOn;

public SchnitzelDBDAO() {
    dbProperties = new Properties();
    String stage = System.getProperty("stage", "prod");
    LOG.info("Loading stage properties: {} ", stage);
    String file = stage + ".settings.txt";
    try (InputStream in = this.getClass().getClassLoader().getResourceAsStream(file)) {
        dbProperties.load(in);
    } catch (Exception e) {
        LOG.error("Properties konnten nicht geladen werden: ", e);
        throw new RuntimeException(e);
    }
    mealsActionPerformedOn=new Vector<Gericht>();
}

private Connection createConnection() throws Exception {
    return DriverManager.getConnection(dbProperties.getProperty("server"), dbProperties);
}

public Vector<Gericht> findGericht(java.util.Date von, java.util.Date bis) throws Exception {
    Vector<Gericht> v = new Vector<Gericht>();
    java.sql.Date[] dates = testDate(von, bis);
    try (Connection connect = createConnection()) {
        LOG.info("Searching for meals");
        String query = "select * from Gericht where date BETWEEN ? and ? order by date asc";
        PreparedStatement statement = connect.prepareStatement(query);

        statement.setDate(1, dates[0]);
        statement.setDate(2, dates[1]);
        ResultSet rs = statement.executeQuery();
        while (rs.next()) {
            Gericht g = new Gericht();
            g.setId(rs.getInt("id"));
            String str = rs.getString("classification");
            g.setClassification(Classification.valueOf(str));
            g.setDate(rs.getDate("date"));
            g.setName(rs.getString("name"));
            g.setPreisExtern(rs.getBigDecimal("preisExtern"));
            g.setPreisIntern(rs.getBigDecimal("preisIntern"));
            v.add(g);
        }

        return v;
    }
}
}

然后在这样的某个类中调用它。第一行是该类中的成员变量；

SchnitzelDBDAO dbConnector = new SchnitzelDBDAO();
dbConnector.remove(gerichte.get(table.getSelectedRow()).getDate());

我希望你能以某种方式调整你的代码以适应我的代码并让你的代码正常工作