带数据库的 Java GUI

Question

我正在尝试创建一个简单的 GUI 程序来访问我的 derby 数据库。

public void viewRecord(int id)
{

    try{
        GET_RECORD = "SELECT * FROM record where id = ?";

        s = c.prepareStatement(GET_RECORD);
        s.setInt(1, id);
        r = s.executeQuery();
        rs = r.getMetaData();

        System.out.printf("%-15d%-15s%-15d%-15s%-15s",r.getInt(1), r.getString(2), r.getInt(3),r.getString(4),r.getString(5));




    }catch (SQLException ex) {
        java.util.logging.Logger.getLogger(Dbase.class.getName()).log(Level.SEVERE, null, ex);
    }
}

每当调用该函数时，我都会得到

java.sql.SQLException: Invalid operation at current cursor position.

我的语法有什么问题吗？谢谢:)

编辑:完整的错误消息(?)

Jan 31, 2016 12:16:15 AM database.project.Dbase viewRecord SEVERE: null java.sql.SQLException: Invalid operation at current cursor position. at org.apache.derby.client.am.SQLExceptionFactory.getSQLException(Unknown Source) at org.apache.derby.client.am.SqlException.getSQLException(Unknown Source) at org.apache.derby.client.am.ClientResultSet.getInt(Unknown Source) at database.project.Dbase.viewRecord(Dbase.java:95) at database.project.viewItem.btnViewActionPerformed(viewItem.java:107) at database.project.viewItem.access$000(viewItem.java:6) at database.project.viewItem$1.actionPerformed(viewItem.java:39) at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:2022) at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2348) at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:402) at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:259) at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:252) at java.awt.Component.processMouseEvent(Component.java:6535) at javax.swing.JComponent.processMouseEvent(JComponent.java:3324) at java.awt.Component.processEvent(Component.java:6300) at java.awt.Container.processEvent(Container.java:2236) at java.awt.Component.dispatchEventImpl(Component.java:4891) at java.awt.Container.dispatchEventImpl(Container.java:2294) at java.awt.Component.dispatchEvent(Component.java:4713) at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4888) at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4525) at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4466) at java.awt.Container.dispatchEventImpl(Container.java:2280) at java.awt.Window.dispatchEventImpl(Window.java:2750) at java.awt.Component.dispatchEvent(Component.java:4713) at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:758) at java.awt.EventQueue.access$500(EventQueue.java:97) at java.awt.EventQueue$3.run(EventQueue.java:709) at java.awt.EventQueue$3.run(EventQueue.java:703) at java.security.AccessController.doPrivileged(Native Method) at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:76) at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:86) at java.awt.EventQueue$4.run(EventQueue.java:731) at java.awt.EventQueue$4.run(EventQueue.java:729) at java.security.AccessController.doPrivileged(Native Method) at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:76) at java.awt.EventQueue.dispatchEvent(EventQueue.java:728) at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:201) at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:116) at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:105) at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101) at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:93) at java.awt.EventDispatchThread.run(EventDispatchThread.java:82) Caused by: ERROR XJ121: Invalid operation at current cursor position. at org.apache.derby.client.am.ClientResultSet.checkForValidCursorPosition(Unknown Source) at org.apache.derby.client.am.ClientResultSet.checkGetterPreconditions(Unknown Source) ... 41 more

Answer 1

您必须使用next 调用。

ResultSet rs = s.executeQuery();
if (rs.next()) {
    rs.getMetaData()...
}

引自the documentation

A ResultSet cursor is initially positioned before the first row; the first call >to the method next makes the first row the current row; the second call makes >the second row the current row, and so on.