如何用JAXB编组注释为@XmlAttachmentRef的DataHandler？
我正在尝试使用JAXB（2.1.12）编组一个具有DataHandler字段的对象。 对于流支持， DataHandler使用@ XmlAttachmentRef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第80 SwaRefAdapter return am.addSwaRefAttachment(data); 和am分配了AttachmentMarshaller am = XMLSerializer.getInstance().attachmentMarshaller; 因此，如果存在@XmlAttachmentRef则attachmentMarshaller似乎为null。
我是否需要以不同的方式设置某些内容，或者以不同的方式使用JAXB API来处理附件？
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的Metro实现中的一个错误（JDK / JRE中包含的RI）。 如果您使用另一个JAXB实现，例如EclipseLink JAXB（MOXy） ，这将正常工作。 要使用EclipseLink MOXy，请将eclipselink.jar（ 此处提供 ）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和AttachmentUnmarshallers来处理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。