java - 我想使用 ArrayList 在我的控制台中显示来自数据库的所有数据

Question

你好，我只想在控制台上显示我的数据库表的全部内容。我试图先从数据库中获取记录并存储在 ArrayList 中，但它不显示任何内容而是显示以下内容:

[com.suven.java.EmployeeDTO@970c0e]
[com.suven.java.EmployeeDTO@970c0e, com.suven.java.EmployeeDTO@987197] 
[com.suven.java.EmployeeDTO@970c0e, com.suven.java.EmployeeDTO@987197, com.suven.java.EmployeeDTO@497904]

我完全不知道该怎么做。我的代码是:

EmployeeDTO java file

public class EmployeeDTO 
{
    //private properties
    private int empNo;
    private String eName;
    private String jobTitle;
    //setters
    public void setEmpNo(int val){empNo=val;}
    public void setEName(String val){eName=val;}
    public void setJob(String val){jobTitle=val;}
    // getters
    public int getEmpNo(){return empNo;}
    public String getEName(){return eName;}
    public String getJob(){return jobTitle;}
}

我的 EmployeeList java 代码是:

public class EmployeeList 
{

  public static void main(String argv[]) 
  {
   Connection conn=null;
   Statement stmt=null;
   ResultSet rs=null;      

   try 
   {
    // Load the JDBC driver  
    // This can be skipped for Derby, but derbyclient.jar has to be in the CLASSPATH   
    Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");
    String accessFileName = "E:/Database/java";
    conn=DriverManager.getConnection("jdbc:odbc:DRIVER={Microsoft Access  Driver (*.mdb, *.accdb)};DBQ="+accessFileName+".accdb;");

    // Build an SQL String 
    String sqlQuery = "SELECT * from Employee"; 

    // Create a Statement object
    stmt = conn.createStatement(); 

    // Execute SQL and get obtain the ResultSet object
    rs = stmt.executeQuery(sqlQuery);  
    ArrayList<EmployeeDTO> employees = new ArrayList<EmployeeDTO>();
    // Process the result set - print Employees
    while (rs.next())
    { 
        EmployeeDTO currentEmp = new EmployeeDTO();

        currentEmp.setEmpNo(rs.getInt("EMPNO"));
        currentEmp.setEName(rs.getString("ENAME"));
        currentEmp.setJob(rs.getString("JOB_TITLE"));
        employees.add(currentEmp);
        System.out.println(employees);
    }       
   } 
   catch( SQLException se ) 
   {
      System.out.println ("SQLError: " + se.getMessage ()+ " code: " + se.getErrorCode ());
   }
   catch( Exception e )
   {
      System.out.println(e.getMessage());
      e.printStackTrace(); 
   }
   finally
   {
       // clean up the system resources
       try
       {
       rs.close();     
       stmt.close(); 
       conn.close();  
       }
       catch(Exception e)
       {
           e.printStackTrace();
       } 
   }
}
}

我的数据库是:

Employee
EMPN     ENAME     JOB_TITLE
1        abc       xyz
2        pqr       mno
3        lmn       hij

请帮助我，我已经发布了完整的代码和数据库我哪里出错了如何在控制台中显示它

Answer 1

您必须在您的 EmployeeDTO 类中实现 toString()。如果您使用的是 Eclipse，则可以生成方法:右键单击类 -> 源代码 -> 生成 toString()...