Question

这是类的构造函数之一。新对象在数据库中创建新记录。当我在源代码中“手动”创建这个对象时，一切都很好。但是当我将创建声明放入按钮的actionlistener时，编译器会返回sql异常。

public Pacjent()
    {
        try
        {
            Connection conn = DataBase.Connect();
            Statement stat = conn.createStatement();
            String addRecord = "INSERT INTO records VALUES (12365, 'Bond', 'James', 'M', '12.41.1953r', 'Londyn', 'none');";
            stat.executeUpdate(addRecord);        
    }
    catch(SQLException e)
    {
        e.printStackTrace();
    }    

}

我得到的例外是

org.postgresql.util.PSQLException：此连接已关闭。在 org.postgresql.jdbc2.AbstractJdbc2Connection.checkClosed（AbstractJdbc2Connection.java:714）在 org.postgresql.jdbc3.AbstractJdbc3Connection.createStatement（AbstractJdbc3Connection.java:230）在 org.postgresql.jdbc2.AbstractJdbc2Connection.createStatement（AbstractJdbc2Connection.java:191）在klasySilnika.Pacjent。（Pacjent.java:61）at klasyInterfejsu.NowaKarta $ 1.actionPerformed（NowaKarta.java:155）at at javax.swing.AbstractButton.fireActionPerformed（AbstractButton.java:2018）在 javax.swing.AbstractButton中的$ Handler.actionPerformed（AbstractButton.java:2341）在 javax.swing.DefaultButtonModel.fireActionPerformed（DefaultButtonModel.java:402）在 javax.swing.DefaultButtonModel.setPressed（DefaultButtonModel.java:259）在 javax.swing.plaf.basic.BasicButtonListener.mouseReleased（BasicButtonListener.java:252）在java.awt.Component.processMouseEvent（Component.java:6504）at javax.swing.JComponent.processMouseEvent（JComponent.java:3321）at java.awt.Component.processEvent（Component.java:6269）at java.awt.Container.processEvent（Container.java:2229）at java.awt.Component.dispatchEventImpl（Component.java:4860）at java.awt.Container.dispatchEventImpl（Container.java:2287）at java.awt.Component.dispatchEvent（Component.java:4686）at java.awt.LightweightDispatcher.retargetMouseEvent（Container.java:4832）在 java.awt.LightweightDispatcher.processMouseEvent（Container.java:4492） at java.awt.LightweightDispatcher.dispatchEvent（Container.java:4422）在java.awt.Container.dispatchEventImpl（Container.java:2273）at java.awt.Window.dispatchEventImpl（Window.java:2713）at java.awt.Component.dispatchEvent（Component.java:4686）at java.awt.EventQueue.dispatchEventImpl（EventQueue.java:707）at at java.awt.EventQueue.access $ 000（EventQueue.java:101）at java.awt.EventQueue $ 3.run（EventQueue.java:666）at java.awt.EventQueue $ 3.run（EventQueue.java:664）at java.security.AccessController.doPrivileged（Native Method）at java.security.ProtectionDomain $ 1.doIntersectionPrivilege（ProtectionDomain.java:76）在 java.security.ProtectionDomain $ 1.doIntersectionPrivilege（ProtectionDomain.java:87）在java.awt.EventQueue $ 4.run（EventQueue.java:680）at java.awt.EventQueue $ 4.run（EventQueue.java:678）at java.security.AccessController.doPrivileged（Native Method）at java.security.ProtectionDomain $ 1.doIntersectionPrivilege（ProtectionDomain.java:76）在java.awt.EventQueue.dispatchEvent（EventQueue.java:677）at java.awt.EventDispatchThread.pumpOneEventForFilters（EventDispatchThread.java:211）在 java.awt.EventDispatchThread.pumpEventsForFilter（EventDispatchThread.java:128）在 java.awt.EventDispatchThread.pumpEventsForHierarchy（EventDispatchThread.java:117）在 java.awt.EventDispatchThread.pumpEvents（EventDispatchThread.java:113）在 java.awt.EventDispatchThread.pumpEvents（EventDispatchThread.java:105）在java.awt.EventDispatchThread.run（EventDispatchThread.java:90）

这是actionlistener：

saveButton.addActionListener
        (
            new ActionListener() 
            {
                @Override
                public void actionPerformed(ActionEvent event) 
                {
                    Pacjent nowy = new Pacjent();
                }
            }
        );

Database.Connect方法：

public class DataBase 
{
    public static Connection Connect()
    {
        return CONNECTION;
    }        

    private static Connection CONNECTION = CreateConnection();

    private static Connection CreateConnection() 
    {
        try 
        {
            Class.forName("org.postgresql.Driver");

            Properties props = new Properties();
            FileInputStream in = new FileInputStream("D:\\projekty\\Arch\\src\\klasySilnika\\bazadanych.properties");
            props.load(in);
            in.close();

            String drivers = props.getProperty("jdbc.drivers");
            if(drivers != null) System.setProperty("jdbc.drivers", drivers);
            String url = props.getProperty("jdbc.url");
            String username = props.getProperty("jdbc.username");
            String password = props.getProperty("jdbc.password");

            return DriverManager.getConnection(url, username,password);
        }
        catch (ClassNotFoundException e) 
        {
            System.out.println("NO JDBC driver");
        return null;
    }
        catch(IOException e)
        {
            System.out.println("Where is properties file?");
            return null;
        } 
        catch(SQLException e)
        {
            System.out.println("error: adress, user, password?");
            return null;
        }
        finally
        {
           // ...   
        }
    }
}

Answer 1

也许连接实例在其他地方关闭，因为你的连接是静态的，整个应用程序只有一个连接实例，所以你可以改变连接到多个实例或通过数据源管理，例如：c3p0，dhcp

Answer 2

public Pacjent()
{
    try
    {
        Connection conn = DataBase.**CreateConnection**();
        Statement stat = conn.createStatement();
        String addRecord = "INSERT INTO records VALUES (12365, 'Bond', 'James', 'M', '12.41.1953r', 'Londyn', 'none');";
        stat.executeUpdate(addRecord);        
}
catch(SQLException e)
{
    e.printStackTrace();
}

}

您可以将方法更改为CreateConnection

java jdbc中的连接异常

2 个答案: