Question

我正在尝试使用JAXB（2.1.12）编组一个具有DataHandler字段的对象。对于流媒体支持，DataHandler使用@ XmlAttachmentRef进行注释。通过Web服务进行序列化和流式处理（JBoss上的Metro）工作正常，但是使用JAXB进行简单的编组却没有。

这是一个精简的例子：

public class DataHandlerAttachmentSerialization {

    @XmlRootElement
    static class RootObject {
        @XmlElement
        @XmlAttachmentRef // Works without this, but required for streaming 
        DataHandler dataHandler = new DataHandler(
                new com.sun.xml.ws.util.ByteArrayDataSource(
                " ".getBytes(), "application/octet-stream"));
    }

    @Test
    public void test() throws JAXBException {
        JAXBContext context = JAXBContext.newInstance(RootObject.class);
        Marshaller marshaller = context.createMarshaller();
        StringWriter writer = new StringWriter();
        marshaller.marshal(new RootObject(), writer);
        Assert.assertNotNull(writer.toString());
    }
}

运行此测试会产生以下堆栈跟踪：

javax.xml.bind.MarshalException
 - with linked exception:
[com.sun.xml.bind.api.AccessorException: java.lang.NullPointerException]
    at com.sun.xml.bind.v2.runtime.MarshallerImpl.write(MarshallerImpl.java:318)
    at com.sun.xml.bind.v2.runtime.MarshallerImpl.marshal(MarshallerImpl.java:244)
    at javax.xml.bind.helpers.AbstractMarshallerImpl.marshal(AbstractMarshallerImpl.java:96)
    ...
Caused by: com.sun.xml.bind.api.AccessorException: java.lang.NullPointerException
    at com.sun.xml.bind.v2.runtime.XMLSerializer.reportError(XMLSerializer.java:246)
    at com.sun.xml.bind.v2.runtime.XMLSerializer.reportError(XMLSerializer.java:261)
    at com.sun.xml.bind.v2.runtime.ClassBeanInfoImpl.serializeBody(ClassBeanInfoImpl.java:335)
    at com.sun.xml.bind.v2.runtime.XMLSerializer.childAsSoleContent(XMLSerializer.java:593)
    at com.sun.xml.bind.v2.runtime.ClassBeanInfoImpl.serializeRoot(ClassBeanInfoImpl.java:320)
    at com.sun.xml.bind.v2.runtime.XMLSerializer.childAsRoot(XMLSerializer.java:494)
    at com.sun.xml.bind.v2.runtime.MarshallerImpl.write(MarshallerImpl.java:315)
    ... 25 more
Caused by: com.sun.xml.bind.api.AccessorException: java.lang.NullPointerException
    at com.sun.xml.bind.v2.runtime.reflect.AdaptedAccessor.get(AdaptedAccessor.java:74)
    at com.sun.xml.bind.v2.runtime.reflect.TransducedAccessor$CompositeTransducedAccessorImpl.writeLeafElement(TransducedAccessor.java:250)
    at com.sun.xml.bind.v2.runtime.property.SingleElementLeafProperty.serializeBody(SingleElementLeafProperty.java:98)
    at com.sun.xml.bind.v2.runtime.ClassBeanInfoImpl.serializeBody(ClassBeanInfoImpl.java:332)
    ... 29 more
Caused by: java.lang.NullPointerException
    at com.sun.xml.bind.v2.runtime.SwaRefAdapter.marshal(SwaRefAdapter.java:80)
    at com.sun.xml.bind.v2.runtime.SwaRefAdapter.marshal(SwaRefAdapter.java:65)
    at com.sun.xml.bind.v2.runtime.reflect.AdaptedAccessor.get(AdaptedAccessor.java:72)
    ... 32 more

SwaRefAdapter中的第80行return am.addSwaRefAttachment(data);，am被AttachmentMarshaller am = XMLSerializer.getInstance().attachmentMarshaller;分配，因此如果attachmentMarshaller @XmlAttachmentRef为空，则此时{{1}}为空存在。

我是否需要以不同的方式设置内容，或以不同的方式使用JAXB API来处理附件？

Answer 1

在JAX-WS环境之外使用JAXB时，JAXB实现应默认将XML文档中的二进制内容内联为base64Binary。

这似乎是JAXB（包含在JDK / JRE中的RI）的Metro实现中的错误。如果您使用其他JAXB实现，例如EclipseLink JAXB (MOXy)，这将正常工作。要使用EclipseLink MOXy，请将eclipselink.jar（available here）添加到类路径中，并在以下内容中添加jaxb.properties文件和模型类：

javax.xml.bind.context.factory=org.eclipse.persistence.jaxb.JAXBContextFactory

JAX-WS注册AttachmentMarshallers＆amp; AttachmentUnmarshallers处理JAXB模型中的二进制内容。如果需要，可以在使用JAXB独立时指定自己的。

http://download.oracle.com/docs/cd/E17409_01/javase/6/docs/api/javax/xml/bind/attachment/AttachmentMarshaller.html

如何使用JAXB编组注释为@XmlAttachmentRef的DataHandler？

1 个答案: