Question

我正在使用一个我无法控制的API，它会返回XML。基本上我有directory个对象，它可以包含多个directory和file个对象，这些对象没有被任何标记包裹，在少数其他原始字段中。 file对象包含少量原始字段，以及由tPathList和oPathList标记包装的2个列表。

以下是此类XML的示例：

<hwreply>
  <result>1</result>
  <directory>
    <file>
      <created>DATE</created>
      <modified>DATE</modified>
      <name>STRING</name>
      <size>INT</size>
      <tPath>STRING</tPath>
      <oPath>STRING</oPath>
      <aPath>STRING</aPath>
      <tPathList> 
        <tPath>STRING</tPath>
        ...
      </tPathList>
      <oPathList> 
        <oPath>STRING</oPath>
        ...
      </oPathList>    
    </file>
    <file>...</file>
    ...
    <directory>...</directory>
    <directory>...</directory>
    ...
    <nEntries>5</nEntries>
    <created>DATE</created>
    <modified>DATE</modified>
  </directory>
</hwreply>

我创建了目录和文件对象，以及作为根的OpenDirectory。当我打电话

OpenDirectory od = response.getEntity(OpenDirectory.class);

我得到以下异常：

Exception in thread "main" java.lang.NullPointerException
    at com.sun.xml.internal.bind.v2.runtime.reflect.Lister$CollectionLister.addToPack(Lister.java:290)
    at com.sun.xml.internal.bind.v2.runtime.reflect.Lister$CollectionLister.addToPack(Lister.java:254)
    at com.sun.xml.internal.bind.v2.runtime.unmarshaller.Scope.add(Scope.java:106)
    at com.sun.xml.internal.bind.v2.runtime.property.ArrayERProperty$ReceiverImpl.receive(ArrayERProperty.java:195)
at com.sun.xml.internal.bind.v2.runtime.unmarshaller.UnmarshallingContext.endElement(UnmarshallingContext.java:507)
at com.sun.xml.internal.bind.v2.runtime.unmarshaller.SAXConnector.endElement(SAXConnector.java:145)
at com.sun.org.apache.xerces.internal.parsers.AbstractSAXParser.endElement(AbstractSAXParser.java:601)
at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl.scanEndElement(XMLDocumentFragmentScannerImpl.java:1782)
at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl$FragmentContentDriver.next(XMLDocumentFragmentScannerImpl.java:2938)
at com.sun.org.apache.xerces.internal.impl.XMLDocumentScannerImpl.next(XMLDocumentScannerImpl.java:648)
at com.sun.org.apache.xerces.internal.impl.XMLNSDocumentScannerImpl.next(XMLNSDocumentScannerImpl.java:140)
at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl.scanDocument(XMLDocumentFragmentScannerImpl.java:511)
at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(XML11Configuration.java:808)
at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(XML11Configuration.java:737)
at com.sun.org.apache.xerces.internal.parsers.XMLParser.parse(XMLParser.java:119)
at com.sun.org.apache.xerces.internal.parsers.AbstractSAXParser.parse(AbstractSAXParser.java:1205)
at com.sun.org.apache.xerces.internal.jaxp.SAXParserImpl$JAXPSAXParser.parse(SAXParserImpl.java:522)
at com.sun.xml.internal.bind.v2.runtime.unmarshaller.UnmarshallerImpl.unmarshal0(UnmarshallerImpl.java:200)
at com.sun.xml.internal.bind.v2.runtime.unmarshaller.UnmarshallerImpl.unmarshal(UnmarshallerImpl.java:173)
at javax.xml.bind.helpers.AbstractUnmarshallerImpl.unmarshal(AbstractUnmarshallerImpl.java:120)
at javax.xml.bind.helpers.AbstractUnmarshallerImpl.unmarshal(AbstractUnmarshallerImpl.java:103)
at com.sun.jersey.core.impl.provider.entity.XMLRootElementProvider.readFrom(XMLRootElementProvider.java:115)
at com.sun.jersey.core.provider.jaxb.AbstractRootElementProvider.readFrom(AbstractRootElementProvider.java:111)
at com.sun.jersey.api.client.ClientResponse.getEntity(ClientResponse.java:553)
at com.sun.jersey.api.client.ClientResponse.getEntity(ClientResponse.java:506)
at liveperson.lphosting.plugins.cdn.proxy.highwinds.HighwindsProxy.getDirectory(HighwindsProxy.java:49)
at liveperson.lphosting.plugins.cdn.proxy.highwinds.HighwindsProxy.main(HighwindsProxy.java:59)

我认为它与我所拥有的其中一个列表有关，但我无法确定哪里出错了。任何帮助将不胜感激。

提前致谢。

以下是课程（减去几个字段/方法）：

@XmlRootElement(name = "hwreply")
public class OpenDirectory extends ResponseBase {

@XmlElement(name="session")
public Session getSession() {...}

public void setSession(Session session) {...}

@XmlElement(name="directory")
public Directory getDirectory() {...}

public void setDirectory(Directory directory) {...}
}



public class Directory {

...
private List<Directory> directories;
private List<File> files;

@XmlElement(name="nEntries")
public int getnEntries() {...}

public void setnEntries(int nEntries) {...}

@XmlElement(name="name")
public String getName() {... }

public void setName(String name) {...  }

@XmlElement(name="readonly")
public boolean isReadonly() {...  }

public void setReadonly(boolean readonly) { ... }

@XmlElement (name="created")
public String getCreated() { ... }

public void setCreated(String created) { ... }

@XmlElement(name="modified")
public String getModified() {... }

public void setModified(String modified) {...    }

@XmlElements(
        @XmlElement(name="directory", type=Directory.class)
)
public List<Directory> getDirectories() {
    return directories;
}

public void setDirectories(List directories) {
    this.directories = directories;
}

@XmlElements(
        @XmlElement(name="file", type=File.class)
)
public List<File> getFiles() {
    return files;
}

public void setFiles(List files) {
    this.files = files;
}
}



public class File {

private List<String> tPathList;
private List<String> oPathList;

@XmlElement(name="xferStatus")
public int getXferStatus() {...}

public void setXferStatus(int xferStatus) {...}

@XmlElement(name="size")
public int getSize() {...}

public void setSize(int size) {...}


@XmlElement(name="tPath")
public String gettPath() {...}

public void settPath(String tPath) {...}

@XmlElement(name="oPath")
public String getoPath() {...}

public void setoPath(String oPath) {...}

@XmlElementWrapper(name="tPathList")
@XmlElements(
        @XmlElement(name="tPath", type=String.class)
)
public List gettPathList() {
    return tPathList;
}

public void settPathList(List tPathList) {...}

@XmlElementWrapper(name="oPathList")
@XmlElements(
        @XmlElement(name="oPath", type=String.class)
)
public List getoPathList() {
    return oPathList;
}

public void setoPathList(List oPathList) {
    this.oPathList = oPathList;
}
}

Answer 1

问题由OP自己解决，并将其作为答案添加。

发现问题。如果它可以帮助任何人：

File类中的

setFiles(List files)应为setFiles(List<File> files)。

Answer 2

我也有同样的例外。但解决方案不同。我在这里分享，为未来的问题解决者。调用JAXBContext.newInstance()时，请查看返回的对象。

通常它应该是com.sun.xml.bind.v2.runtime.JAXBContextImpl类型。但是，如果它来自一些glassfish3库，如：

jar:file.../glassfish3/glassfish/modules/jaxb-osgi.jar

给了我同样的例外。改变了类路径的顺序，如果JAXBContext.newInstance()从这个jar中找到第一个实现JAXBContext类，最后解组工作正常：

jar:file:.../.m2/repository/com/sun/xml/bind/jaxb-impl/2.x.x/jaxb-impl-2.x.x.jar

帮助排除JAXB解组NPE的故障

2 个答案: