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由於某些原因，我在閱讀java代碼中的xml文件時遇到困難。下面的方法試圖使用jdom庫來設置和返回一個根元素。但是當我運行junit測試並期望代碼打印根目錄時，它會給我一個由Wurzel = document.getRootElement();引起的空指針異常。我真的很感謝這裏的幫助。順便說一句，路徑是正確的，該文件沒有奇怪的結構，不包含錯誤。所以沒有問題。我在這裏閱讀了一些關於junit測試和nullpointerexception的其他主題。是沒有太大的help..thx提前junit nullpointerexception同時在java中讀取xml
public void SetWurzel() {
builder = new SAXBuilder();
xmlFile = new File(Pfad);
try {
document = (Document) builder.build(xmlFile);
}
catch (IOException e) {
JOptionPane
.showMessageDialog(
null,
"Bitte prüfen Sie die Zugriffsrechte auf Ihre Datei und geben "
+ "Sie diese gegebenenfalls frei. ");
} catch (JDOMException e) {
JOptionPane
.showMessageDialog(
null,
"Bitte Prüfen Sie die Struktur der einzulesenden XMLDatei auf Fehlern"
+ " und fehlende Elemente.");
}
Wurzel = document.getRootElement();
}
public Element GetWurzel() {
return Wurzel;
}
，這裏是在其上運行JUnit測試IM。
@Before
public void testSetPfad() {
this.input = new XML_Input();
}
@Test
public void testsetWurzel() {
input.setPfad("C:\\Users\\me\\workspace\\Workspace_uni\\Tests\\test1.xml");
input.SetWurzel();
System.out.println(input.GetWurzel().getText());
}
使曾建議earcam更改後，我得到了下面的異常堆棧跟蹤：
java.io.FileNotFoundException:
C:\Users\arm\workspace\Workspace_uni\Tests\test1.xml (Das System kann den angegebenen Pfad nicht finden)
at java.io.FileInputStream.open(Native Method)
at java.io.FileInputStream.<init>(FileInputStream.java:146)
at java.io.FileInputStream.<init>(FileInputStream.java:101)
at sun.net.www.protocol.file.FileURLConnection.connect(FileURLConnection.java:90)
at sun.net.www.protocol.file.FileURLConnection.getInputStream(FileURLConnection.java:188)
at com.sun.org.apache.xerces.internal.impl.XMLEntityManager.setupCurrentEntity(XMLEntityManager.java:619)
at com.sun.org.apache.xerces.internal.impl.XMLVersionDetector.determineDocVersion(XMLVersionDetector.java:189)
at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(XML11Configuration.java:812)
at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(XML11Configuration.java:777)
at com.sun.org.apache.xerces.internal.parsers.XMLParser.parse(XMLParser.java:141)
at com.sun.org.apache.xerces.internal.parsers.AbstractSAXParser.parse(AbstractSAXParser.java:1213)
at com.sun.org.apache.xerces.internal.jaxp.SAXParserImpl$JAXPSAXParser.parse(SAXParserImpl.java:648)
at org.jdom2.input.sax.SAXBuilderEngine.build(SAXBuilderEngine.java:217)
at org.jdom2.input.sax.SAXBuilderEngine.build(SAXBuilderEngine.java:277)
at org.jdom2.input.sax.SAXBuilderEngine.build(SAXBuilderEngine.java:264)
at org.jdom2.input.SAXBuilder.build(SAXBuilder.java:1116)
at File_Processing_Component.XML_Input.SetWurzel(XML_Input.java:68)
at File_Processing_Component.XML_InputTest.testSetWurzelThrowFileNotFoundExceptionException(XML_InputTest.java:31)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:606)
at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:50)
at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47)
at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
at org.junit.internal.runners.statements.ExpectException.evaluate(ExpectException.java:19)
at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:26)
at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:325)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:78)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:57)
at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290)
at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71)
at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)
at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58)
at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268)
at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:50)
at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:459)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:675)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:382)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:192)
後的異常堆棧trace..that會幫助別人找到解決你的問題。 – Lucky