Domanda

Sto sviluppando una serie di classi Java che devono serializzare a XML nel seguente formato:

<foo value="123"/>

<!-- or this -->
<bar value="abc"/>

<!-- or this -->
<baz value="true"/>

All'inizio, Foo.java Sembrava qualcosa del genere:

@XmlRootElement
@XmlAccessorType(XmlAccessType.FIELD)
class Foo {
    @XmlAttribute
    String value;

    // snip constructors

    // snip methods
    // getValue
    // equals, hashCode, toString
    // static valueOf(String), static valueOf(int)
}

Non ci vuole molta immaginazione per indovinare cosa Bar.java e Baz.java potrebbe sembrare. Queste sono classi di avvolgimento molto semplici per (in questo esempio) int, String, e boolean. Fino a questo punto, tutto è hunky Dory. Dopo aver scritto il nono round di

class WhoCares {
    @XmlAttribute
    Whatever value;
    /* 2 constructors */
    /* 6 methods found in every one of these classes */
}

Ho pensato: "Ehi, so come posso risolvere questo - ho solo bisogno di un livello di astrazione!" Presentazione Wrapper<T>:

abstract class Wrapper<T> {
    @XmlAttribute
    private T value;

    Wrapper() {} // default ctor for JAXB
    Wrapper(T value) {
        this.value = value;
    }

    T getValue() {
        return value;
    }

    // snip equals, hashCode, toString
}

Ora, per implementare Foo, tutto quello che devo fare è estendersi Wrapper, Implementa i metodi di fabbrica di cui ho bisogno:

class Foo extends Wrapper<String> {
    // snip constructors

    static Foo valueOf(String value) {
        return new Foo(value);
    }
}

e aggiungi un @XmlSeeAlso({... Foo.class ...}) a WrapperDichiarazione.

  • PRO: Questo è molto più bello.
  • Con: Jaxb non serializzerà questi oggetti.

Qualsiasi chiamata a JAXBContext.getInstance(Wrapper.class) o JAXBContext.getInstance(Foo.class) fallimento a causa di un file NullPointerException gettato da qualche parte in profondità nelle viscere di jaxb:

17:06:03,706 ERROR [org.apache.catalina.core.ContainerBase.[jboss.web].[localhost].[/Redacted].[JAX-RS Servlet]] Servlet.service() for servlet JAX-RS Servlet threw exception: java.lang.NullPointerException
    at com.sun.xml.bind.v2.runtime.reflect.TransducedAccessor.get(TransducedAccessor.java:165) [:2.2]
    at com.sun.xml.bind.v2.runtime.property.AttributeProperty.<init>(AttributeProperty.java:87) [:2.2]
    at com.sun.xml.bind.v2.runtime.property.PropertyFactory.create(PropertyFactory.java:104) [:2.2]
    at com.sun.xml.bind.v2.runtime.ClassBeanInfoImpl.<init>(ClassBeanInfoImpl.java:179) [:2.2]
    at com.sun.xml.bind.v2.runtime.JAXBContextImpl.getOrCreate(JAXBContextImpl.java:515) [:2.2]
    at com.sun.xml.bind.v2.runtime.ClassBeanInfoImpl.<init>(ClassBeanInfoImpl.java:166) [:2.2]
    at com.sun.xml.bind.v2.runtime.JAXBContextImpl.getOrCreate(JAXBContextImpl.java:515) [:2.2]
    at com.sun.xml.bind.v2.runtime.JAXBContextImpl.getOrCreate(JAXBContextImpl.java:534) [:2.2]
    at com.sun.xml.bind.v2.runtime.property.SingleElementNodeProperty.<init>(SingleElementNodeProperty.java:101) [:2.2]
    at sun.reflect.GeneratedConstructorAccessor49.newInstance(Unknown Source) [:1.6.0_24]
    at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27) [:1.6.0_24]
    at java.lang.reflect.Constructor.newInstance(Constructor.java:513) [:1.6.0_24]
    at com.sun.xml.bind.v2.runtime.property.PropertyFactory.create(PropertyFactory.java:124) [:2.2]
    at com.sun.xml.bind.v2.runtime.ClassBeanInfoImpl.<init>(ClassBeanInfoImpl.java:179) [:2.2]
    at com.sun.xml.bind.v2.runtime.JAXBContextImpl.getOrCreate(JAXBContextImpl.java:515) [:2.2]
    at com.sun.xml.bind.v2.runtime.ClassBeanInfoImpl.<init>(ClassBeanInfoImpl.java:166) [:2.2]
    at com.sun.xml.bind.v2.runtime.JAXBContextImpl.getOrCreate(JAXBContextImpl.java:515) [:2.2]
    at com.sun.xml.bind.v2.runtime.JAXBContextImpl.<init>(JAXBContextImpl.java:330) [:2.2]
    at com.sun.xml.bind.v2.runtime.JAXBContextImpl$JAXBContextBuilder.build(JAXBContextImpl.java:1140) [:2.2]
    at com.sun.xml.bind.v2.ContextFactory.createContext(ContextFactory.java:154) [:2.2]
    at com.sun.xml.bind.v2.ContextFactory.createContext(ContextFactory.java:121) [:2.2]
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) [:1.6.0_24]
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39) [:1.6.0_24]
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) [:1.6.0_24]
    at java.lang.reflect.Method.invoke(Method.java:597) [:1.6.0_24]
    at javax.xml.bind.ContextFinder.newInstance(ContextFinder.java:201) [:1.0.0.Final]
    at javax.xml.bind.ContextFinder.find(ContextFinder.java:362) [:1.0.0.Final]
    at javax.xml.bind.JAXBContext.newInstance(JAXBContext.java:618) [:1.0.0.Final]
    at javax.xml.bind.JAXBContext.newInstance(JAXBContext.java:565) [:1.0.0.Final]
    at com.sun.jersey.core.provider.jaxb.AbstractJAXBProvider.getStoredJAXBContext(AbstractJAXBProvider.java:189) [:1.6]
    at com.sun.jersey.core.provider.jaxb.AbstractJAXBProvider.getJAXBContext(AbstractJAXBProvider.java:182) [:1.6]
    at com.sun.jersey.core.provider.jaxb.AbstractJAXBProvider.getMarshaller(AbstractJAXBProvider.java:160) [:1.6]
    at com.sun.jersey.core.provider.jaxb.AbstractJAXBProvider.getMarshaller(AbstractJAXBProvider.java:139) [:1.6]
    at com.sun.jersey.core.provider.jaxb.AbstractRootElementProvider.writeTo(AbstractRootElementProvider.java:151) [:1.6]
    at com.sun.jersey.spi.container.ContainerResponse.write(ContainerResponse.java:306) [:1.6]
    at com.sun.jersey.server.impl.application.WebApplicationImpl._handleRequest(WebApplicationImpl.java:1310) [:1.6]
    at com.sun.jersey.server.impl.application.WebApplicationImpl.handleRequest(WebApplicationImpl.java:1223) [:1.6]
    at com.sun.jersey.server.impl.application.WebApplicationImpl.handleRequest(WebApplicationImpl.java:1213) [:1.6]
    at com.sun.jersey.spi.container.servlet.WebComponent.service(WebComponent.java:414) [:1.6]
    at com.sun.jersey.spi.container.servlet.ServletContainer.service(ServletContainer.java:537) [:1.6]
    at com.sun.jersey.spi.container.servlet.ServletContainer.service(ServletContainer.java:699) [:1.6]
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:847) [:1.0.0.Final]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:324) [:6.0.0.Final]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:242) [:6.0.0.Final]
    at com.example.mgp.filter.RetryFilter.doFilter(RetryFilter.java:109) [:]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:274) [:6.0.0.Final]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:242) [:6.0.0.Final]
    at com.example.mgp.filter.AuthFilter.doFilter(AuthFilter.java:57) [:]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:274) [:6.0.0.Final]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:242) [:6.0.0.Final]
    at org.jboss.weld.servlet.ConversationPropagationFilter.doFilter(ConversationPropagationFilter.java:67) [:6.0.0.Final]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:274) [:6.0.0.Final]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:242) [:6.0.0.Final]
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:275) [:6.0.0.Final]
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191) [:6.0.0.Final]
    at org.jboss.web.tomcat.security.SecurityAssociationValve.invoke(SecurityAssociationValve.java:181) [:6.0.0.Final]
    at org.jboss.modcluster.catalina.CatalinaContext$RequestListenerValve.event(CatalinaContext.java:285) [:1.1.0.Final]
    at org.jboss.modcluster.catalina.CatalinaContext$RequestListenerValve.invoke(CatalinaContext.java:261) [:1.1.0.Final]
    at org.jboss.web.tomcat.security.JaccContextValve.invoke(JaccContextValve.java:88) [:6.0.0.Final]
    at org.jboss.web.tomcat.security.SecurityContextEstablishmentValve.invoke(SecurityContextEstablishmentValve.java:100) [:6.0.0.Final]
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127) [:6.0.0.Final]
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102) [:6.0.0.Final]
    at org.jboss.web.tomcat.service.jca.CachedConnectionValve.invoke(CachedConnectionValve.java:158) [:6.0.0.Final]
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109) [:6.0.0.Final]
    at org.jboss.web.tomcat.service.request.ActiveRequestResponseCacheValve.invoke(ActiveRequestResponseCacheValve.java:53) [:6.0.0.Final]
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:362) [:6.0.0.Final]
    at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:877) [:6.0.0.Final]
    at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:654) [:6.0.0.Final]
    at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:951) [:6.0.0.Final]
    at java.lang.Thread.run(Thread.java:662) [:1.6.0_24]

Ho già provato a cambiare la mia implementazione JAXB da Metro a Moxy (e l'ho fatto Verificare che l'implementazione sia cambiata) ma un NPE simile viene lanciato con moxy:

17:46:48,481 SEVERE [com.sun.jersey.spi.container.ContainerResponse] Mapped exception to response: 500 (Internal Server Error): javax.ws.rs.WebApplicationException: javax.xml.bind.MarshalException
 - with linked exception:
[Exception [EclipseLink-25003] (Eclipse Persistence Services - 2.2.0.v20110202-r8913): org.eclipse.persistence.exceptions.XMLMarshalException
Exception Description: An error occurred marshalling the object
Internal Exception: java.lang.NullPointerException]
    at com.sun.jersey.core.provider.jaxb.AbstractRootElementProvider.writeTo(AbstractRootElementProvider.java:159) [:1.6]
    at com.sun.jersey.spi.container.ContainerResponse.write(ContainerResponse.java:306) [:1.6]
    at com.sun.jersey.server.impl.application.WebApplicationImpl._handleRequest(WebApplicationImpl.java:1310) [:1.6]
    at com.sun.jersey.server.impl.application.WebApplicationImpl.handleRequest(WebApplicationImpl.java:1223) [:1.6]
    at com.sun.jersey.server.impl.application.WebApplicationImpl.handleRequest(WebApplicationImpl.java:1213) [:1.6]
    at com.sun.jersey.spi.container.servlet.WebComponent.service(WebComponent.java:414) [:1.6]
    at com.sun.jersey.spi.container.servlet.ServletContainer.service(ServletContainer.java:537) [:1.6]
    at com.sun.jersey.spi.container.servlet.ServletContainer.service(ServletContainer.java:699) [:1.6]
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:847) [:1.0.0.Final]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:324) [:6.0.0.Final]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:242) [:6.0.0.Final]
    at com.example.mgp.filter.RetryFilter.doFilter(RetryFilter.java:109) [:]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:274) [:6.0.0.Final]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:242) [:6.0.0.Final]
    at com.example.mgp.filter.AuthFilter.doFilter(AuthFilter.java:57) [:]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:274) [:6.0.0.Final]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:242) [:6.0.0.Final]
    at org.jboss.weld.servlet.ConversationPropagationFilter.doFilter(ConversationPropagationFilter.java:67) [:6.0.0.Final]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:274) [:6.0.0.Final]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:242) [:6.0.0.Final]
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:275) [:6.0.0.Final]
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191) [:6.0.0.Final]
    at org.jboss.web.tomcat.security.SecurityAssociationValve.invoke(SecurityAssociationValve.java:181) [:6.0.0.Final]
    at org.jboss.modcluster.catalina.CatalinaContext$RequestListenerValve.event(CatalinaContext.java:285) [:1.1.0.Final]
    at org.jboss.modcluster.catalina.CatalinaContext$RequestListenerValve.invoke(CatalinaContext.java:261) [:1.1.0.Final]
    at org.jboss.web.tomcat.security.JaccContextValve.invoke(JaccContextValve.java:88) [:6.0.0.Final]
    at org.jboss.web.tomcat.security.SecurityContextEstablishmentValve.invoke(SecurityContextEstablishmentValve.java:100) [:6.0.0.Final]
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127) [:6.0.0.Final]
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102) [:6.0.0.Final]
    at org.jboss.web.tomcat.service.jca.CachedConnectionValve.invoke(CachedConnectionValve.java:158) [:6.0.0.Final]
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109) [:6.0.0.Final]
    at org.jboss.web.tomcat.service.request.ActiveRequestResponseCacheValve.invoke(ActiveRequestResponseCacheValve.java:53) [:6.0.0.Final]
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:362) [:6.0.0.Final]
    at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:877) [:6.0.0.Final]
    at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:654) [:6.0.0.Final]
    at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:951) [:6.0.0.Final]
    at java.lang.Thread.run(Thread.java:662) [:1.6.0_24]
Caused by: javax.xml.bind.MarshalException
 - with linked exception:
[Exception [EclipseLink-25003] (Eclipse Persistence Services - 2.2.0.v20110202-r8913): org.eclipse.persistence.exceptions.XMLMarshalException
Exception Description: An error occurred marshalling the object
Internal Exception: java.lang.NullPointerException]
    at org.eclipse.persistence.jaxb.JAXBMarshaller.marshal(JAXBMarshaller.java:314) [:2.2.0.v20110202-r8913]
    at com.sun.jersey.core.provider.jaxb.AbstractRootElementProvider.writeTo(AbstractRootElementProvider.java:179) [:1.6]
    at com.sun.jersey.core.provider.jaxb.AbstractRootElementProvider.writeTo(AbstractRootElementProvider.java:157) [:1.6]
    ... 36 more
Caused by: Exception [EclipseLink-25003] (Eclipse Persistence Services - 2.2.0.v20110202-r8913): org.eclipse.persistence.exceptions.XMLMarshalException
Exception Description: An error occurred marshalling the object
Internal Exception: java.lang.NullPointerException
    at org.eclipse.persistence.exceptions.XMLMarshalException.marshalException(XMLMarshalException.java:78) [:2.2.0.v20110202-r8913]
    at org.eclipse.persistence.oxm.XMLMarshaller.marshal(XMLMarshaller.java:516) [:2.2.0.v20110202-r8913]
    at org.eclipse.persistence.jaxb.JAXBMarshaller.marshal(JAXBMarshaller.java:312) [:2.2.0.v20110202-r8913]
    ... 38 more
Caused by: java.lang.NullPointerException
    at org.eclipse.persistence.oxm.record.OutputStreamRecord.outputStreamWrite(OutputStreamRecord.java:511) [:2.2.0.v20110202-r8913]
    at org.eclipse.persistence.oxm.record.OutputStreamRecord.openStartElement(OutputStreamRecord.java:159) [:2.2.0.v20110202-r8913]
    at org.eclipse.persistence.internal.oxm.XPathNode.startElement(XPathNode.java:330) [:2.2.0.v20110202-r8913]
    at org.eclipse.persistence.internal.oxm.XMLCompositeObjectMappingNodeValue.marshalSingleValue(XMLCompositeObjectMappingNodeValue.java:185) [:2.2.0.v20110202-r8913]
    at org.eclipse.persistence.internal.oxm.XMLCompositeObjectMappingNodeValue.marshal(XMLCompositeObjectMappingNodeValue.java:116) [:2.2.0.v20110202-r8913]
    at org.eclipse.persistence.internal.oxm.NodeValue.marshal(NodeValue.java:104) [:2.2.0.v20110202-r8913]
    at org.eclipse.persistence.internal.oxm.record.ObjectMarshalContext.marshal(ObjectMarshalContext.java:60) [:2.2.0.v20110202-r8913]
    at org.eclipse.persistence.internal.oxm.XPathNode.marshal(XPathNode.java:322) [:2.2.0.v20110202-r8913]
    at org.eclipse.persistence.internal.oxm.TreeObjectBuilder.marshalAttributes(TreeObjectBuilder.java:338) [:2.2.0.v20110202-r8913]
    at org.eclipse.persistence.internal.oxm.XPathNode.startElement(XPathNode.java:344) [:2.2.0.v20110202-r8913]
    at org.eclipse.persistence.internal.oxm.XMLCompositeObjectMappingNodeValue.marshalSingleValue(XMLCompositeObjectMappingNodeValue.java:167) [:2.2.0.v20110202-r8913]
    at org.eclipse.persistence.internal.oxm.XMLCompositeObjectMappingNodeValue.marshal(XMLCompositeObjectMappingNodeValue.java:116) [:2.2.0.v20110202-r8913]
    at org.eclipse.persistence.internal.oxm.NodeValue.marshal(NodeValue.java:104) [:2.2.0.v20110202-r8913]
    at org.eclipse.persistence.internal.oxm.record.ObjectMarshalContext.marshal(ObjectMarshalContext.java:60) [:2.2.0.v20110202-r8913]
    at org.eclipse.persistence.internal.oxm.XPathNode.marshal(XPathNode.java:322) [:2.2.0.v20110202-r8913]
    at org.eclipse.persistence.internal.oxm.TreeObjectBuilder.buildRow(TreeObjectBuilder.java:325) [:2.2.0.v20110202-r8913]
    at org.eclipse.persistence.internal.oxm.XMLAnyObjectMappingNodeValue.marshalSingleValue(XMLAnyObjectMappingNodeValue.java:154) [:2.2.0.v20110202-r8913]
    at org.eclipse.persistence.internal.oxm.XMLAnyObjectMappingNodeValue.marshal(XMLAnyObjectMappingNodeValue.java:70) [:2.2.0.v20110202-r8913]
    at org.eclipse.persistence.internal.oxm.NodeValue.marshal(NodeValue.java:104) [:2.2.0.v20110202-r8913]
    at org.eclipse.persistence.internal.oxm.record.ObjectMarshalContext.marshal(ObjectMarshalContext.java:60) [:2.2.0.v20110202-r8913]
    at org.eclipse.persistence.internal.oxm.XPathNode.marshal(XPathNode.java:322) [:2.2.0.v20110202-r8913]
    at org.eclipse.persistence.internal.oxm.TreeObjectBuilder.buildRow(TreeObjectBuilder.java:325) [:2.2.0.v20110202-r8913]
    at org.eclipse.persistence.oxm.XMLMarshaller.marshal(XMLMarshaller.java:932) [:2.2.0.v20110202-r8913]
    at org.eclipse.persistence.oxm.XMLMarshaller.marshal(XMLMarshaller.java:486) [:2.2.0.v20110202-r8913]
    ... 39 more

Esiste un modo per produrre l'XML richiesto minimizzando la piastra della caldaia e rimane ASCIUTTO?

È stato utile?

Soluzione

Il problema che stai vedendo è dovuto a bug sia nella metropolitana (implementazione di riferimento) che Eclipselink Moxy Implementazioni Jaxb. Il bug moxy rilevante è:

Una cosa da notare sul caso d'uso è che per la cancellazione del tipo, un'implementazione JAXB tratterà la proprietà Value come oggetto di tipo. Ciò significa che le operazioni del maresciallo funzioneranno per te, ma un'operazione non marshal restituirà il valore come stringa. Questo è il motivo per cui se il campo Value è stato annotato con @xmlelement che XSI: le informazioni del tipo verrebbero incluse per preservare le informazioni del tipo:

Moxy WOULOund

Orlansi il bug moxy sfruttando il seguente xmladapter:

import javax.xml.bind.annotation.adapters.XmlAdapter;

public class ObjectAdapter extends XmlAdapter<Object, Object> {

    @Override
    public Object unmarshal(Object v) throws Exception {
        return v;
    }

    @Override
    public Object marshal(Object v) throws Exception {
        return v;
    }

}

L'adattatore XML è registrato sulla tua proprietà come segue:

import javax.xml.bind.annotation.XmlAccessType;
import javax.xml.bind.annotation.XmlAccessorType;
import javax.xml.bind.annotation.XmlAttribute;
import javax.xml.bind.annotation.XmlSeeAlso;
import javax.xml.bind.annotation.XmlTransient;
import javax.xml.bind.annotation.adapters.XmlJavaTypeAdapter;

@XmlTransient
@XmlAccessorType(XmlAccessType.FIELD)
@XmlSeeAlso(Foo.class)
abstract class Wrapper<T> {

    @XmlAttribute
    @XmlJavaTypeAdapter(ObjectAdapter.class)
    private T value;

    Wrapper() {} // default ctor for JAXB

    public Wrapper(T t) {
        value = t;
    }

}
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