&引用；AWT-EventQueue-0“；mysql.connector上的java.lang.NullPointerException。java@5.1.38-bin/com.mysql.jdbc.ResultSetImpl.getDate（ResultSetImpl.java:2015）

在

记录填充
中，您会得到一个
结果集rs
。然后，调用
rs.getDate（2）未检查结果集中是否有记录。调用
rs.next（）
应该可以解决这个问题

您必须处理查询也没有返回任何行的情况。所以应该是这样的

Already in database

Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
    at mysql.connector.java@5.1.38-bin/com.mysql.jdbc.ResultSetImpl.getDate(ResultSetImpl.java:2015)
    at mysql.connector.java@5.1.38-bin/com.mysql.jdbc.ResultSetImpl.getDate(ResultSetImpl.java:1978)
    at DBManager.recordFill(DBManager.java:60)
    at ProjectDetails$3.actionPerformed(ProjectDetails.java:221)
    at java.desktop/javax.swing.JTextField.fireActionPerformed(JTextField.java:508)
    at java.desktop/javax.swing.JTextField.postActionEvent(JTextField.java:723)
    at java.desktop/javax.swing.JTextField$NotifyAction.actionPerformed(JTextField.java:839)
    at java.desktop/javax.swing.SwingUtilities.notifyAction(SwingUtilities.java:1810)
    at java.desktop/javax.swing.JComponent.processKeyBinding(JComponent.java:2900)
    at java.desktop/javax.swing.JComponent.processKeyBindings(JComponent.java:2948)
    at java.desktop/javax.swing.JComponent.processKeyEvent(JComponent.java:2862)
    at java.desktop/java.awt.Component.processEvent(Component.java:6413)
    at java.desktop/java.awt.Container.processEvent(Container.java:2263)
    at java.desktop/java.awt.Component.dispatchEventImpl(Component.java:5012)
    at java.desktop/java.awt.Container.dispatchEventImpl(Container.java:2321)
    at java.desktop/java.awt.Component.dispatchEvent(Component.java:4844)
    at java.desktop/java.awt.KeyboardFocusManager.redispatchEvent(KeyboardFocusManager.java:1950)
    at java.desktop/java.awt.DefaultKeyboardFocusManager.dispatchKeyEvent(DefaultKeyboardFocusManager.java:870)
    at java.desktop/java.awt.DefaultKeyboardFocusManager.preDispatchKeyEvent(DefaultKeyboardFocusManager.java:1139)
    at java.desktop/java.awt.DefaultKeyboardFocusManager.typeAheadAssertions(DefaultKeyboardFocusManager.java:1009)
    at java.desktop/java.awt.DefaultKeyboardFocusManager.dispatchEvent(DefaultKeyboardFocusManager.java:835)
    at java.desktop/java.awt.Component.dispatchEventImpl(Component.java:4893)
    at java.desktop/java.awt.Container.dispatchEventImpl(Container.java:2321)
    at java.desktop/java.awt.Window.dispatchEventImpl(Window.java:2762)
    at java.desktop/java.awt.Component.dispatchEvent(Component.java:4844)
    at java.desktop/java.awt.EventQueue.dispatchEventImpl(EventQueue.java:772)
    at java.desktop/java.awt.EventQueue$4.run(EventQueue.java:721)
    at java.desktop/java.awt.EventQueue$4.run(EventQueue.java:715)
    at java.base/java.security.AccessController.doPrivileged(AccessController.java:391)
    at java.base/java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:85)
    at java.base/java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:95)
    at java.desktop/java.awt.EventQueue$5.run(EventQueue.java:745)
    at java.desktop/java.awt.EventQueue$5.run(EventQueue.java:743)
    at java.base/java.security.AccessController.doPrivileged(AccessController.java:391)
    at java.base/java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:85)
    at java.desktop/java.awt.EventQueue.dispatchEvent(EventQueue.java:742)
    at java.desktop/java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:203)
    at java.desktop/java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:124)
    at java.desktop/java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:113)
    at java.desktop/java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:109)
    at java.desktop/java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101)
    at java.desktop/java.awt.EventDispatchThread.run(EventDispatchThread.java:90)

我怀疑数据库中的值是
null
。您是否尝试过更新到MySQL Connector/J的较新版本，版本5.1.38相当旧。虽然这是处理结果集的正确方法，但在这种情况下，驱动程序不应该抛出
NullPointerException
（它应该抛出一个
SQLException
。这可能是驱动程序中的一个bug，升级到新版本可能是个好主意。
Already in database

Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
    at mysql.connector.java@5.1.38-bin/com.mysql.jdbc.ResultSetImpl.getDate(ResultSetImpl.java:2015)
    at mysql.connector.java@5.1.38-bin/com.mysql.jdbc.ResultSetImpl.getDate(ResultSetImpl.java:1978)
    at DBManager.recordFill(DBManager.java:60)
    at ProjectDetails$3.actionPerformed(ProjectDetails.java:221)
    at java.desktop/javax.swing.JTextField.fireActionPerformed(JTextField.java:508)
    at java.desktop/javax.swing.JTextField.postActionEvent(JTextField.java:723)
    at java.desktop/javax.swing.JTextField$NotifyAction.actionPerformed(JTextField.java:839)
    at java.desktop/javax.swing.SwingUtilities.notifyAction(SwingUtilities.java:1810)
    at java.desktop/javax.swing.JComponent.processKeyBinding(JComponent.java:2900)
    at java.desktop/javax.swing.JComponent.processKeyBindings(JComponent.java:2948)
    at java.desktop/javax.swing.JComponent.processKeyEvent(JComponent.java:2862)
    at java.desktop/java.awt.Component.processEvent(Component.java:6413)
    at java.desktop/java.awt.Container.processEvent(Container.java:2263)
    at java.desktop/java.awt.Component.dispatchEventImpl(Component.java:5012)
    at java.desktop/java.awt.Container.dispatchEventImpl(Container.java:2321)
    at java.desktop/java.awt.Component.dispatchEvent(Component.java:4844)
    at java.desktop/java.awt.KeyboardFocusManager.redispatchEvent(KeyboardFocusManager.java:1950)
    at java.desktop/java.awt.DefaultKeyboardFocusManager.dispatchKeyEvent(DefaultKeyboardFocusManager.java:870)
    at java.desktop/java.awt.DefaultKeyboardFocusManager.preDispatchKeyEvent(DefaultKeyboardFocusManager.java:1139)
    at java.desktop/java.awt.DefaultKeyboardFocusManager.typeAheadAssertions(DefaultKeyboardFocusManager.java:1009)
    at java.desktop/java.awt.DefaultKeyboardFocusManager.dispatchEvent(DefaultKeyboardFocusManager.java:835)
    at java.desktop/java.awt.Component.dispatchEventImpl(Component.java:4893)
    at java.desktop/java.awt.Container.dispatchEventImpl(Container.java:2321)
    at java.desktop/java.awt.Window.dispatchEventImpl(Window.java:2762)
    at java.desktop/java.awt.Component.dispatchEvent(Component.java:4844)
    at java.desktop/java.awt.EventQueue.dispatchEventImpl(EventQueue.java:772)
    at java.desktop/java.awt.EventQueue$4.run(EventQueue.java:721)
    at java.desktop/java.awt.EventQueue$4.run(EventQueue.java:715)
    at java.base/java.security.AccessController.doPrivileged(AccessController.java:391)
    at java.base/java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:85)
    at java.base/java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:95)
    at java.desktop/java.awt.EventQueue$5.run(EventQueue.java:745)
    at java.desktop/java.awt.EventQueue$5.run(EventQueue.java:743)
    at java.base/java.security.AccessController.doPrivileged(AccessController.java:391)
    at java.base/java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:85)
    at java.desktop/java.awt.EventQueue.dispatchEvent(EventQueue.java:742)
    at java.desktop/java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:203)
    at java.desktop/java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:124)
    at java.desktop/java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:113)
    at java.desktop/java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:109)
    at java.desktop/java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101)
    at java.desktop/java.awt.EventDispatchThread.run(EventDispatchThread.java:90)

if (rs.next()) {
    // row found, handle row
} else {
    // row not found, maybe throw exception
}