JAVA：数据库结果集保持返回零行

Question

我通过使用驱动程序正在加载并正在建立连接的存根进行验证。我的方法查询数据库正在执行没有错误，但返回一个5列和0行（我通过调试验证）的空结果集。测试数据库中有4条记录，包含5列，我的查询要求返回所有结果。我可能会感到疲倦......对我缺少什么有所了解？这里是查询方法。数据库文件是访问.mdb

public ArrayList fillResults（） { ArrayList savedData = new ArrayList（）; Statement stmt = null; ResultSet results = null;

try 
    { 
     stmt = conn.createStatement(); 
     results = stmt.executeQuery(SELECT_ALL); 
     while(results.next()) 
     { 
      for(short i = 0; i < 5; i++) 
      { 
       savedData.add(results.getString(i)); 
      } 
     } 

    } 
    catch(SQLException ex) 
    { 
     JOptionPane.showMessageDialog(null, ex.getMessage() + ": error during retrieval."); 
    } 
    finally 
    {   
     try 
     { 
      results.close(); 
      stmt.close(); 
     } catch (SQLException e){} 
    } 

    return savedData; 
} 

Answer 1

您不应该退回ResultSet。并且持久化类不应该包含Swing JOptionPane。

试试这样说：

package persistence; 

import java.sql.Connection; 
import java.sql.ResultSet; 
import java.sql.SQLException; 
import java.sql.Statement; 
import java.util.ArrayList; 
import java.util.List; 

public class JdbcDemo 
{ 
    private static final String SELECT_SAVED_DATA = "select * from saveData"; 

    private Connection connection; 

    public JdbcDemo(Connection connection) 
    { 
     this.connection = connection; 
    } 

    public List<String> getSavedData() throws SQLException 
    { 
     List<String> savedData = new ArrayList<String>(); 

     Statement stmt = null; 
     ResultSet rs = null; 
     try 
     { 
      stmt = this.connection.createStatement(); 
      rs = stmt.executeQuery(SELECT_SAVED_DATA); 
      while (rs.next()) 
      { 
       savedData.add(rs.getString(1)); // modify this as needed 
      } 
     } 
     finally 
     { 
      DatabaseUtils.close(rs); 
      DatabaseUtils.close(stmt); 
     } 

     return savedData; 
    } 
}