Question

我是Java和MongoDB世界的新手。我可以成功地在我的Mngodb中插入数据，但如果我在按钮下编写这个简单的代码，我会收到此错误： Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException

这是我的代码块：

private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {                                         
        Morphia morphia=new Morphia();
        Datastore  ds2 = morphia.createDatastore(mongo,"rcfdb");          
        Query q=ds2.createQuery(District.class).field("Name").equal(jTextField1.getText());
}

如果我删除这一行，那么它可以正常工作：

Datastore  ds2 = morphia.createDatastore(mongo,"rcfdb");

你可以帮我解决这个问题吗？你能告诉我如何在另一个标签中显示这个查询的结果吗？

非常感谢

更新

Jul 09, 2013 5:16:43 PM com.google.code.morphia.logging.MorphiaLoggerFactory chooseLoggerFactory
INFO: LoggerImplFactory set to com.google.code.morphia.logging.jdk.JDKLoggerFactory
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
    at com.google.code.morphia.DatastoreImpl.<init>(DatastoreImpl.java:79)
    at com.google.code.morphia.DatastoreImpl.<init>(DatastoreImpl.java:90)
    at com.google.code.morphia.Morphia.createDatastore(Morphia.java:170)
    at com.google.code.morphia.Morphia.createDatastore(Morphia.java:177)
    at rcf.mongodb.TestForm.jButton1ActionPerformed(TestForm.java:94)
    at rcf.mongodb.TestForm.access$100(TestForm.java:17)
    at rcf.mongodb.TestForm$2.actionPerformed(TestForm.java:53)
    at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:2018)
    at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2341)
    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.AWTEventMulticaster.mouseReleased(AWTEventMulticaster.java:289)
    at java.awt.Component.processMouseEvent(Component.java:6505)
    at javax.swing.JComponent.processMouseEvent(JComponent.java:3321)
    at java.awt.Component.processEvent(Component.java:6270)
    at java.awt.Container.processEvent(Container.java:2229)
    at java.awt.Component.dispatchEventImpl(Component.java:4861)
    at java.awt.Container.dispatchEventImpl(Container.java:2287)
    at java.awt.Component.dispatchEvent(Component.java:4687)
    at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4832)
    at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4492)
    at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4422)
    at java.awt.Container.dispatchEventImpl(Container.java:2273)
    at java.awt.Window.dispatchEventImpl(Window.java:2719)
    at java.awt.Component.dispatchEvent(Component.java:4687)
    at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:729)
    at java.awt.EventQueue.access$200(EventQueue.java:103)
    at java.awt.EventQueue$3.run(EventQueue.java:688)
    at java.awt.EventQueue$3.run(EventQueue.java:686)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
    at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:87)
    at java.awt.EventQueue$4.run(EventQueue.java:702)
    at java.awt.EventQueue$4.run(EventQueue.java:700)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
    at java.awt.EventQueue.dispatchEvent(EventQueue.java:699)
    at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:242)
    at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:161)
    at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:150)
    at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:146)
    at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:138)
    at java.awt.EventDispatchThread.run(EventDispatchThread.java:91)
BUILD SUCCESSFUL (total time: 11 seconds)

我尝试在MongoDB上进行查询时出现异常

0 个答案: