爲什麼dom4j僅在我的測試環境中爲有效的XPath拋出InvalidXPathException？

Question

我正在爲某些代碼編寫一些單元測試，這些代碼是在系統中工作的，但我在InvalidXPathException上遇到了有效XPath的問題。

使用//external|//inline從DOM4J文檔中提取出某些元素，它在生產環境中工作，但不在我的測試環境中工作。不應該有問題，因爲它是我在環境之外測試的有效XPath。

任何幫助，將不勝感激！

的JUnit/EasyMock的測試：

@Test 
public void testgetDCR_success(){ 
    RequestContext context = EasyMock.createMock(RequestContext.class); 
    FileDal dal = EasyMock.createMock(FileDal.class); 
    String xmlContent = "<xml>your sample stuff</xml>"; 
    Document sampleDoc = Dom4jUtils.newDocument(xmlContent); 

    InputStream stream = null; 
    try { 
     stream = new ByteArrayInputStream(xmlContent.getBytes("UTF-8")); 
    } catch(IOException e) { 
     Assert.fail("Could not open file stream for test."); 
    } 

    EasyMock.expect(context.getFileDal()).andReturn(dal).anyTimes(); 
    EasyMock.expect(dal.getRoot()).andReturn("").anyTimes(); 
    EasyMock.expect(dal.getSeparator()).andReturn('/').anyTimes(); 
    EasyMock.expect(dal.exists("/some/path")).andReturn(true); 
    EasyMock.expect(dal.read("/some/path")).andReturn(xmlContent); 

    EasyMock.expect(dal.getStream("some/path")).andReturn(stream); 
    EasyMock.replay(context); 
    EasyMock.replay(dal); 

    Document doc = new DefaultTransformationService().getDCR(context, "some/path"); 

    Assert.assertEquals(sampleDoc, doc); 
} 

攻向問題：

@Override 
public Document getDCR(RequestContext context, String relativePath) { 
    LOGGER.debug(">> getDCR"); 

    if (StringUtils.isBlank(relativePath)) { 
     LOGGER.error("No origin file path given"); 
     LOGGER.debug("<< getDCR"); 
     return null; 
    } 

    Document dcrDoc = null; 
    try { 
     dcrDoc = ExternalUtils.readXmlFile(context, relativePath); 
    }catch (RuntimeException e){ 
     LOGGER.error("No DCR found at file path: "+relativePath,e); 
     LOGGER.debug("<< getDCR"); 
     return null; 
    } 

    if (dcrDoc == null) { 
     LOGGER.error("Unable to open xml file: " + relativePath); 
     LOGGER.debug("<< getDCR"); 
     return null; 
    } 
    LOGGER.debug("<< getDCR"); 

    Set<String> parsedPaths = new HashSet<String>(); 
    parsedPaths.add(relativePath); 

    return parseData(context, dcrDoc, parsedPaths); 
} 

private Document parseData(RequestContext context, Document dcr, Set<String> parsedPaths) { 
    LOGGER.debug(">> parseData"); 

    // get all nodes that would be converted. 
    @SuppressWarnings("unchecked") 
    List<Element> elements = dcr.selectNodes("//external|//inline"); 

    // For each of the nodes present within the document that are of type external or inline 
    for (Element element : elements) { 
     // process each element in the list of selected elements. 
     processElement(context, element, parsedPaths); 
    } 

    LOGGER.debug("<< parseData"); 
    return dcr; 
} 

堆棧跟蹤：

org.dom4j.InvalidXPathException: Invalid XPath expression:  '//external|//inline'. Caused by: org/jaxen/dom4j/Dom4jXPath 
at org.dom4j.xpath.DefaultXPath.parse(DefaultXPath.java:362) 
at org.dom4j.xpath.DefaultXPath.<init>(DefaultXPath.java:59) 
at org.dom4j.DocumentFactory.createXPath(DocumentFactory.java:230) 
at org.dom4j.tree.AbstractNode.createXPath(AbstractNode.java:207) 
at org.dom4j.tree.AbstractNode.selectNodes(AbstractNode.java:164) 
at com.sample.project.service.impl.DefaultTransformationService.parseData(DefaultTransformationService.java:163) 
at com.sample.project.service.impl.DefaultTransformationService.getDCR(DefaultTransformationService.java:144) 
at com.sample.project.service.impl.DefaultTransformationServiceTest.testgetDCR_success(DefaultTransformationServiceTest.java:84) 
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) 
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source) 
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) 
at java.lang.reflect.Method.invoke(Unknown Source) 
at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:47) 
at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12) 
at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:44) 
at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17) 
at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:271) 
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:70) 
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:50) 
at org.junit.runners.ParentRunner$3.run(ParentRunner.java:238) 
at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:63) 
at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:236) 
at org.junit.runners.ParentRunner.access$000(ParentRunner.java:53) 
at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:229) 
at org.junit.runners.ParentRunner.run(ParentRunner.java:309) 
at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:86) 
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) 

Answer 1

望着DOM4J源代碼，可以看出，該異常的根本原因不一定是無效的XPath表達式：

protected static XPath parse(String text) { 
    try { 
     return new Dom4jXPath(text); 
    } catch (JaxenException e) { 
     throw new InvalidXPathException(text, e.getMessage()); 
    } catch (Throwable t) { 
     throw new InvalidXPathException(text, t); 
    } 
} 

並給出了消息的外觀，可以得出結論Throwable被捕獲。從InvalidXPathException：

public InvalidXPathException(String xpath, Throwable t) { 
    super("Invalid XPath expression: '" + xpath 
      + "'. Caused by: " + t.getMessage()); 
} 

不幸的是，DOM4J隱藏在這種情況下，原來的異常，但

Caused by: org/jaxen/dom4j/Dom4jXPath 

意味着原來的異常是一個NoClassDefFoundError錯誤。

然而，奇怪的是，Dom4jXPath無法找到，而明顯發現JaxenException（因爲他們生活在同一個jar（jaxen））。無論如何，它看起來像你的類路徑沒有正確設置。

順便說一句，前面的「分析」是基於DOM4J 1.6.1。，所以如果你使用另一個版本YMMV。