令人难以置信:无法从X类转换为其超类 [英] Unbelievable: Cannot cast from class X to its super class

问题描述

我在使用Spring(3.0.1.RELEASE)，TestNG(5.11)和Maven Surefire(2.5)时遇到一个非常奇怪的问题. 我有一个测试类，该类扩展了用于testNG的Spring助手类，以便可以从xml文件(包含一些bean定义)中加载测试上下文. 我的项目已使用m2eclipse导入到eclipse中(使用Import Maven Project) 该类在Eclipse TestNG运行程序中运行良好. 但是，它会在Maven Surefire中引发此异常

I'm encountering a very weird problem with Spring (3.0.1.RELEASE), TestNG (5.11) and Maven Surefire (2.5). I have a test class that extends a Spring helper class for testNG so that test context can be loaded from an xml file (that contains some bean definitions). My project was imported into eclipse using m2eclipse (using Import Maven Project) The class run fine in Eclipse TestNG runner. However, it throws this exception with Maven Surefire

Caused by: java.lang.ClassCastException: com.sun.org.apache.xerces.internal.jaxp.DocumentBuilderFactoryImpl cannot be cast to javax.xml.parsers.DocumentBuilderFactory
 at javax.xml.parsers.DocumentBuilderFactory.newInstance(DocumentBuilderFactory.java:123)
 at org.springframework.beans.factory.xml.DefaultDocumentLoader.createDocumentBuilderFactory(DefaultDocumentLoader.java:89)
 at org.springframework.beans.factory.xml.DefaultDocumentLoader.loadDocument(DefaultDocumentLoader.java:70)
 at org.springframework.beans.factory.xml.XmlBeanDefinitionReader.doLoadBeanDefinitions(XmlBeanDefinitionReader.java:388)

我消除了pom中所有涉及的依赖项，因此这两个类 com.sun.org.apache.xerces.internal.jaxp.DocumentBuilderFactoryImpl和 javax.xml.parsers.DocumentBuilderFactory仅来自JRE(rt.jar).

I have eliminated all involved dependencies in my pom so that the two classes com.sun.org.apache.xerces.internal.jaxp.DocumentBuilderFactoryImpl and javax.xml.parsers.DocumentBuilderFactory are coming from JRE only (the rt.jar).

所以，这对我来说真是令人难以置信.

So, it looks so unbelievable to me.

我想知道加载类中是否有任何机制可以解释这种现象?

I wonder if there is any mechanism in loading class that can explain for this behavior?

谢谢.

已更新:这是我的依赖项树:

Updated: Here is my dependency tree:

[INFO] org.seamoo:seamoo-webapp:war:1.0-SNAPSHOT
[INFO] +- com.google.appengine:appengine-api-1.0-sdk:jar:1.3.1:compile
[INFO] +- com.google.gwt:gwt-servlet:jar:2.0.3:compile
[INFO] +- com.google.gwt:gwt-user:jar:2.0.3:provided
[INFO] +- org.apache.geronimo.specs:geronimo-servlet_2.5_spec:jar:1.2:provided
[INFO] +- org.slf4j:slf4j-api:jar:1.5.6:compile
[INFO] +- ch.qos.logback:logback-classic:jar:0.9.15:compile
[INFO] |  \- ch.qos.logback:logback-core:jar:0.9.15:compile
[INFO] +- org.springframework:spring-webmvc:jar:3.0.1.RELEASE:compile
[INFO] |  +- org.springframework:spring-asm:jar:3.0.1.RELEASE:compile
[INFO] |  +- org.springframework:spring-beans:jar:3.0.1.RELEASE:compile
[INFO] |  +- org.springframework:spring-context:jar:3.0.1.RELEASE:compile
[INFO] |  |  \- org.springframework:spring-aop:jar:3.0.1.RELEASE:compile
[INFO] |  +- org.springframework:spring-core:jar:3.0.1.RELEASE:compile
[INFO] |  |  \- commons-logging:commons-logging:jar:1.1.1:compile
[INFO] |  +- org.springframework:spring-expression:jar:3.0.1.RELEASE:compile
[INFO] |  \- org.springframework:spring-web:jar:3.0.1.RELEASE:compile
[INFO] |     \- aopalliance:aopalliance:jar:1.0:compile
[INFO] +- org.springframework:spring-context-support:jar:3.0.1.RELEASE:compile
[INFO] +- org.apache.tiles:tiles-jsp:jar:2.1.4:compile
[INFO] |  \- org.apache.tiles:tiles-servlet:jar:2.1.4:compile
[INFO] +- org.apache.tiles:tiles-portlet:jar:2.1.4:compile
[INFO] |  \- org.apache.tiles:tiles-core:jar:2.1.4:compile
[INFO] |     +- org.apache.tiles:tiles-api:jar:2.1.4:compile
[INFO] |     +- commons-digester:commons-digester:jar:1.8.1:compile
[INFO] |     |  \- commons-beanutils:commons-beanutils:jar:1.8.0:compile
[INFO] |     \- commons-logging:commons-logging-api:jar:1.1:compile
[INFO] +- org.apache.tomcat:jasper-el:jar:6.0.26:compile
[INFO] |  \- org.apache.tomcat:el-api:jar:6.0.26:compile
[INFO] +- org.freemarker:freemarker:jar:2.3.16:compile
[INFO] +- org.tuckey:urlrewritefilter:jar:3.1.0:compile
[INFO] +- org.seamoo.utils:converter:jar:0.1:compile
[INFO] +- junit:junit:jar:4.6:test
[INFO] +- org.springframework:spring-test:jar:3.0.1.RELEASE:test
[INFO] +- org.testng:testng:jar:jdk15:5.11:test
[INFO] +- net.sourceforge.htmlunit:htmlunit:jar:2.7:test
[INFO] |  +- commons-collections:commons-collections:jar:3.2.1:test
[INFO] |  +- commons-lang:commons-lang:jar:2.4:test
[INFO] |  +- commons-httpclient:commons-httpclient:jar:3.1:test
[INFO] |  +- commons-codec:commons-codec:jar:1.4:test
[INFO] |  +- net.sourceforge.htmlunit:htmlunit-core-js:jar:2.7:test
[INFO] |  +- net.sourceforge.nekohtml:nekohtml:jar:1.9.14:test
[INFO] |  +- net.sourceforge.cssparser:cssparser:jar:0.9.5:test
[INFO] |  |  \- org.w3c.css:sac:jar:1.3:test
[INFO] |  \- commons-io:commons-io:jar:1.4:test
[INFO] +- org.jbehave:jbehave-core:jar:2.5:test
[INFO] |  +- junit:junit-dep:jar:4.4:test
[INFO] |  \- org.hamcrest:hamcrest-all:jar:1.1:test
[INFO] +- org.mockito:mockito-all:jar:1.8.4:test
[INFO] +- org.powermock.modules:powermock-module-testng:jar:1.3.7:test
[INFO] |  \- org.powermock:powermock-core:jar:1.3.7:test
[INFO] |     +- org.powermock.reflect:powermock-reflect:jar:1.3.7:test
[INFO] |     |  \- org.objenesis:objenesis:jar:1.2:test
[INFO] |     \- javassist:javassist:jar:3.10.0.GA:test
[INFO] +- org.powermock.api:powermock-api-mockito:jar:1.3.7:test
[INFO] |  \- org.powermock.api:powermock-api-support:jar:1.3.7:test
[INFO] +- org.workingonit:gwtbridge:jar:0.1:compile
[INFO] +- org.seleniumhq.selenium.client-drivers:selenium-java-testng-helper:jar:1.0.1:test
[INFO] |  \- org.seleniumhq.selenium.client-drivers:selenium-java-client-driver:jar:1.0.1:test
[INFO] +- com.dyuproject:dyuproject-util:jar:1.1-SNAPSHOT:compile
[INFO] +- com.dyuproject:dyuproject-openid:jar:1.1-SNAPSHOT:compile
[INFO] +- org.mortbay.jetty:jetty-util:jar:6.1.22:compile
[INFO] +- org.seamoo:seamoo-model:jar:1.0-SNAPSHOT:compile
[INFO] |  +- javax.jdo:jdo2-api:jar:2.3-eb:compile
[INFO] |  +- javax.transaction:jta:jar:1.1:compile
[INFO] |  \- com.google.appengine:geronimo-jpa_3.0_spec:jar:1.1.1:compile
[INFO] +- org.seamoo:seamoo-persistence:jar:1.0-SNAPSHOT:compile
[INFO] |  +- com.google.appengine.orm:datanucleus-appengine:jar:1.0.5.final:compile
[INFO] |  +- org.datanucleus:datanucleus-core:jar:1.1.5:compile
[INFO] |  \- com.google.appengine:datanucleus-jpa:jar:1.1.5:runtime
[INFO] +- org.seamoo:seamoo-theme:jar:1.0-SNAPSHOT:compile
[INFO] \- org.seamoo:seamoo-test-resources:jar:1.0-SNAPSHOT:test
[INFO]    +- com.google.appengine:appengine-api-labs:jar:1.3.1:test
[INFO]    +- com.google.appengine:appengine-api-stubs:jar:1.3.1:test
[INFO]    \- com.google.appengine:appengine-testing:jar:1.3.1:test

我可以确定我已经消除了所有可能的jar，因为当我使用Eclipse的Open Type功能时，它建议每个DocumentBuilderFactory和DocumentBuilderFactoryImpl

I can sure that I have eliminate all possible jars because when I use Open Type feature of Eclipse, it suggests only 1 class for each of DocumentBuilderFactory and DocumentBuilderFactoryImpl

推荐答案

我在DocumentBuilderFactoryImpl中遇到了类似的问题.我最初还假定原因是类路径中的冲突，但这实际上是PowerMock创建类的检测版本(并且在类加载器中具有两个不兼容版本的类)的结果.我没有使用@PowerMockIgnore的运气，但最终通过使用JAXP将任何对象移动到非静态方法(例如，使用@Before而不是@BeforeClass来实例化该对象)来解决了该问题.

I had a similar problem with DocumentBuilderFactoryImpl. I also initially assumed the cause was a conflict in the classpath, but it was actually a result of PowerMock creating an instrumented version of the class (and having two incompatible versions of the class in the classloader). I had no luck using the @PowerMockIgnore, but eventually fixed the problem by moving any object using JAXP into non-static methods (e.g. using @Before and not @BeforeClass to instantiate the object).

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