结果集已关闭

时间：2014-08-07 04:40:06

标签： java jdbc

这段代码告诉我：

private void jButton4ActionPerformed(java.awt.event.ActionEvent evt) {      

    String UI=null;

    String sql="select * from Outcome";
    try {
        sta=con.createStatement();
    } catch (SQLException ex) {
        Logger.getLogger(Main.class.getName()).log(Level.SEVERE, null, ex);
    }
    try {
        rs=sta.executeQuery(sql);
    } catch (SQLException ex) {
        Logger.getLogger(Main.class.getName()).log(Level.SEVERE, null, ex);
    }
    try {

        while(rs.next()){
             UI=rs.getString("OutID");
            if(UI.equals(jTextField5.getText())){
                System.out.println("\n"+UI);
          UI=jTextField5.getText();
            String Des=jTextField6.getText();
            String Mo=jTextField7.getText();
            String Da=String.valueOf(jComboBox4.getSelectedItem())+"/"+String.valueOf(jComboBox5.getSelectedItem())+"/"+String.valueOf(jComboBox6.getSelectedItem());
           String Not=jTextField8.getText();

            String st = String.format("UPDATE Outcome SET OutID = '%s', Description = '%s', MoneyAmount = '%s', ODate = '%s', Notes = '%s'",UI,Des,Mo,Da,Not);
                  sta.executeUpdate(st);

          //  ps.setString(1, jTextField5.getText());
            //ps.setString(2,jTextField6.getText());
           // ps.setString(3,jTextField7.getText());
            //ps.setString(4,String.valueOf(jComboBox4.getSelectedItem()+"/"+String.valueOf(jComboBox5.getSelectedItem())+"/"+String.valueOf(jComboBox6.getSelectedItem())));

                sta.close();

                con.close();

            }


        }
    } catch (SQLException ex) {
        Logger.getLogger(Main.class.getName()).log(Level.SEVERE, null, ex);
    }


}

例外：

java.sql.SQLException: ‏‏[Microsoft][ODBC Driver Manager] ‏‏حالة رأس المؤشر غير صالحة
at sun.jdbc.odbc.JdbcOdbc.createSQLException(Unknown Source)
at sun.jdbc.odbc.JdbcOdbc.standardError(Unknown Source)
at sun.jdbc.odbc.JdbcOdbc.SQLGetDataString(Unknown Source)
at sun.jdbc.odbc.JdbcOdbcResultSet.getDataString(Unknown Source)
at sun.jdbc.odbc.JdbcOdbcResultSet.getString(Unknown Source)
at sun.jdbc.odbc.JdbcOdbcResultSet.getString(Unknown Source)
at comcentrt.Outcomes.jButton4ActionPerformed(Outcomes.java:861)
at comcentrt.Outcomes.access$3(Outcomes.java:846)
at comcentrt.Outcomes$5.actionPerformed(Outcomes.java:380)
at javax.swing.AbstractButton.fireActionPerformed(Unknown Source)
at javax.swing.AbstractButton$Handler.actionPerformed(Unknown Source)
at javax.swing.DefaultButtonModel.fireActionPerformed(Unknown Source)
at javax.swing.DefaultButtonModel.setPressed(Unknown Source)
at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(Unknown Source)
at java.awt.Component.processMouseEvent(Unknown Source)
at javax.swing.JComponent.processMouseEvent(Unknown Source)
at java.awt.Component.processEvent(Unknown Source)
at java.awt.Container.processEvent(Unknown Source)
at java.awt.Component.dispatchEventImpl(Unknown Source)
at java.awt.Container.dispatchEventImpl(Unknown Source)
at java.awt.Component.dispatchEvent(Unknown Source)
at java.awt.LightweightDispatcher.retargetMouseEvent(Unknown Source)
at java.awt.LightweightDispatcher.processMouseEvent(Unknown Source)
at java.awt.LightweightDispatcher.dispatchEvent(Unknown Source)
at java.awt.Container.dispatchEventImpl(Unknown Source)
at java.awt.Window.dispatchEventImpl(Unknown Source)
at java.awt.Component.dispatchEvent(Unknown Source)
at java.awt.EventQueue.dispatchEventImpl(Unknown Source)
at java.awt.EventQueue.access$200(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
at java.awt.EventQueue$4.run(Unknown Source)
at java.awt.EventQueue$4.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
at java.awt.EventQueue.dispatchEvent(Unknown Source)
at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.run(Unknown Source)

3 个答案:

答案 0 :(得分：1)

您已关闭while循环内的连接

con.close();

这就是你得到例外的原因。 在while循环之后关闭它

while(rs.next())
{
 // your code
}
con.close();

答案 1 :(得分：1)

有一些问题，但让我们开始讨论可能导致问题的原因...... 

while(rs.next()){
    UI=rs.getString("OutID");
    if(UI.equals(jTextField5.getText())){
        System.out.println("\n"+UI);
        //...
        sta.executeUpdate(st);

        // This probably won't help...
        sta.close();
        // This will definitely not help...
        con.close();
    }

}

您正在关闭生成Statement的基础ResultSet，但更重要的是，您正在关闭实际Connection，因此下次您致电{{1}时}，rs.next将被报告为已关闭...

也... 

ResultSet

将关闭之前的String st = String.format("UPDATE Outcome SET OutID = '%s', Description = '%s', MoneyAmount = '%s', ODate = '%s', Notes = '%s'",UI,Des,Mo,Da,Not); sta.executeUpdate(st); （感谢Mark Rotteveel）。如果JDBC驱动程序和数据库支持，您可以使用ResultSet方法之一，例如...... 

Result#updateXxx

请查看Retrieving and Modifying Values from Result Sets了解更多详情......

如果JDBC驱动程序/数据库不支持此功能，则需要创建一个新的rs.update("OutID", UI); 来执行操作。

另外，以这种方式格式化Statement并以这种方式在数据库语句中使用它...... 

String

真的非常危险。它让您容易受到SQL注入攻击。相反，您应该使用Prepared Statements

此外，您的资源管理还不够理想......

看看这个...... 

String st = String.format("UPDATE Outcome SET OutID = '%s', Description = '%s', MoneyAmount = '%s', ODate = '%s', Notes = '%s'",UI,Des,Mo,Da,Not);

如果try { sta=con.createStatement(); } catch (SQLException ex) { Logger.getLogger(Main.class.getName()).log(Level.SEVERE, null, ex); } try { rs=sta.executeQuery(sql); } catch (SQLException ex) { Logger.getLogger(Main.class.getName()).log(Level.SEVERE, null, ex); } 抛出异常会怎样？现在，当您尝试拨打createStatement

时，您有可能NullPointerException

看看这个...... 

executeQuery

如果在致电try { while(rs.next()){ if(UI.equals(jTextField5.getText())){ sta.close(); con.close(); } } } catch (SQLException ex) { Logger.getLogger(Main.class.getName()).log(Level.SEVERE, null, ex); } 之前抛出异常会怎样？在这样的close语句中调用close是非常危险的，因为它可能意味着这些资源永远不会被关闭。

相反，你可以使用Java 7 try-catch ... 

try-with-resources

请查看The try-with-resources Statement了解详情

或者，如果您不使用Java 7，则必须按照旧学校的方式进行，并使用try (Statement sta = con.createStatement()) { try (ResultSet rs = sta.executeQuery(sql)) { while (rs.next()) { UI = rs.getString("OutID"); if (UI.equals(jTextField5.getText())) { System.out.println("\n" + UI); UI = jTextField5.getText(); String Des = jTextField6.getText(); String Mo = jTextField7.getText(); String Da = String.valueOf(jComboBox4.getSelectedItem()) + "/" + String.valueOf(jComboBox5.getSelectedItem()) + "/" + String.valueOf(jComboBox6.getSelectedItem()); String Not = jTextField8.getText(); String st = String.format("UPDATE Outcome SET OutID = '%s', Description = '%s', MoneyAmount = '%s', ODate = '%s', Notes = '%s'", UI, Des, Mo, Da, Not); sta.executeUpdate(st); } } } } catch (SQLException ex) { ex.printStackTrace(); } 

try-catch-finally

在任何一种情况下都可以保证，无论发生什么（JVM在执行中死亡），都会尝试关闭资源。

答案 2 :(得分：-3)

Dataconnection dbconnect = new Dataconnection();
Connection con = null;
PreparedStatement ps = null;
ResultSet rs = null;

try {
    con = dbconnect.getConnection();
    ps = con.prepareStatement("query");
    rs = ps.executeQuery();

    while(rs.next()) 
    {

    }

} catch (Exception e)
{
    System.out.println(e.getMessage());
    e.printStackTrace();
} finally 
{
    try {
        if (rs != null) 
        {
            rs.close();
            rs = null;
        }
        if (ps != null) 
        {
            ps.close();
            ps = null;
        }
        if (con != null)
        {
            con.close();
            con = null;
        }
    } catch (Exception ee)
    {
        System.out.println(ee.getMessage());
        ee.printStackTrace();
    }
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