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我正在构建Java SWT应用程序。作为整个过程的一部分,我正在处理一个具有特定格式来处理事物的excel文件。我想要的是我的JFrame上的一个链接,它触发下载一个存储在我的项目中的示例excel文件,无需本地或Internet依赖。我不知道我能做到这一点。FileUtils.copyURLToFile不适用于项目文件
我已经试过这个FileUtils.copyURLToFile,但它是抛出空指针异常。我正在显示我的代码。任何帮助将不胜感激。
public void actionPerformed(ActionEvent arg0) {
log("clicked to download");
String temp_path = System.getProperty("user.dir")+"\\resources\\EmailSheet.xlsx";
log("path = " + temp_path);
URL inputUrl = getClass().getResource(temp_path);
log("URL = " +inputUrl.toString());
File dest = new File("D:/new_file.xlsx");
try {
FileUtils.copyURLToFile(inputUrl, dest);
} catch (IOException e) {
log("Error saving sample file : " + e.getMessage().toString());
e.printStackTrace();
}
}
我的控制台打印此错误
Mon Oct 03 09:14:29 IST 2016 : clicked to download
Exception in thread "AWT-EventQueue-0" Mon Oct 03 09:14:29 IST 2016 : path = \resources\EmailSheet.xlsx
java.lang.NullPointerException
at tech.excelemail.com.TechExcelEmailApp$7.actionPerformed(TechExcelEmailApp.java:221)
at javax.swing.AbstractButton.fireActionPerformed(Unknown Source)
at javax.swing.AbstractButton$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$500(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(Unknown Source)
at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(Unknown Source)
at java.awt.EventQueue$4.run(Unknown Source)
at java.awt.EventQueue$4.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$JavaSecurityAccessImpl.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)
我想知道是否有错误在我的代码。或者如果我走错了路。如果你认为遗漏未指明的东西,请问我什么。
在此先感谢。
哪行代码在221行? –
您是否在IDE中调试过您的代码,该代码会告诉您在空对象上运行的位置。 – mhasan
请参见[什么是堆栈跟踪,以及如何使用它来调试我的应用程序错误?](http://stackoverflow.com/q/3988788/418556)&[什么是空指针异常,以及如何修复它?](http://stackoverflow.com/q/218384/418556) –