Jersey 2 enum as method parameter throws exception

Question

I'm currently migrating a jersey 1.x project to 2.4.1 and got an error when using enums as parameter (PathParam, QueryParam etc). Basically the this enum should be valid based on jersey's 3rd requirement for method parameter that

Have a static method named valueOf or fromString that accepts a single String argument (see, for example, Integer.valueOf(String) and java.util.UUID.fromString(String));

Since this project uses an xsd as contract to generate the java classes, i have:

<xs:simpleType name="status">
    <xs:restriction base="xs:string">
        <xs:enumeration value="ACTIVE" />
        <xs:enumeration value="INACTIVE" />
    </xs:restriction>
</xs:simpleType>

which generates:

@XmlType(name = "status")
@XmlEnum
public enum Status {

    ACTIVE,
    INACTIVE;

    public String value() {
        return name();
    }

    public static Status fromValue(String v) {
        return valueOf(v);
    }

}

when it's used in:

@GET
public Response search(@QueryParam("status") my.package.Status status) {
//..other code here
}

it produces:

org.glassfish.jersey.server.internal.inject.ExtractorException: Error unmarshalling JAXB object of type "class my.package.Status".
    at org.glassfish.jersey.server.internal.inject.JaxbStringReaderProvider$RootElementProvider$1.fromString(JaxbStringReaderProvider.java:195)
    at org.glassfish.jersey.server.internal.inject.AbstractParamValueExtractor.convert(AbstractParamValueExtractor.java:138)
    at org.glassfish.jersey.server.internal.inject.AbstractParamValueExtractor.fromString(AbstractParamValueExtractor.java:129)
    at org.glassfish.jersey.server.internal.inject.SingleValueExtractor.extract(SingleValueExtractor.java:83)
    at org.glassfish.jersey.server.internal.inject.QueryParamValueFactoryProvider$QueryParamValueFactory.provide(QueryParamValueFactoryProvider.java:88)
    at org.glassfish.jersey.server.spi.internal.ParameterValueHelper.getParameterValues(ParameterValueHelper.java:81)
    at org.glassfish.jersey.server.model.internal.JavaResourceMethodDispatcherProvider$AbstractMethodParamInvoker.getParamValues(JavaResourceMethodDispatcherProvider.java:121)
    at org.glassfish.jersey.server.model.internal.JavaResourceMethodDispatcherProvider$ResponseOutInvoker.doDispatch(JavaResourceMethodDispatcherProvider.java:152)
    at org.glassfish.jersey.server.model.internal.AbstractJavaResourceMethodDispatcher.dispatch(AbstractJavaResourceMethodDispatcher.java:104)
    at org.glassfish.jersey.server.model.ResourceMethodInvoker.invoke(ResourceMethodInvoker.java:367)
    at org.glassfish.jersey.server.model.ResourceMethodInvoker.apply(ResourceMethodInvoker.java:349)
    at org.glassfish.jersey.server.model.ResourceMethodInvoker.apply(ResourceMethodInvoker.java:106)
    at org.glassfish.jersey.server.ServerRuntime$1.run(ServerRuntime.java:259)
    at org.glassfish.jersey.internal.Errors$1.call(Errors.java:271)
    at org.glassfish.jersey.internal.Errors$1.call(Errors.java:267)
    at org.glassfish.jersey.internal.Errors.process(Errors.java:315)
    at org.glassfish.jersey.internal.Errors.process(Errors.java:297)
    at org.glassfish.jersey.internal.Errors.process(Errors.java:267)
    at org.glassfish.jersey.process.internal.RequestScope.runInScope(RequestScope.java:318)
    at org.glassfish.jersey.server.ServerRuntime.process(ServerRuntime.java:236)
    at org.glassfish.jersey.server.ApplicationHandler.handle(ApplicationHandler.java:983)
    at org.glassfish.jersey.servlet.WebComponent.service(WebComponent.java:361)
    at org.glassfish.jersey.servlet.ServletContainer.service(ServletContainer.java:372)
    at org.glassfish.jersey.servlet.ServletContainer.service(ServletContainer.java:335)
    at org.glassfish.jersey.servlet.ServletContainer.service(ServletContainer.java:218)
    at org.mortbay.jetty.servlet.ServletHolder.handle(ServletHolder.java:511)
    at org.mortbay.jetty.servlet.ServletHandler.handle(ServletHandler.java:401)
    at org.mortbay.jetty.security.SecurityHandler.handle(SecurityHandler.java:216)
    at org.mortbay.jetty.servlet.SessionHandler.handle(SessionHandler.java:182)
    at org.mortbay.jetty.handler.ContextHandler.handle(ContextHandler.java:766)
    at org.mortbay.jetty.webapp.WebAppContext.handle(WebAppContext.java:450)
    at org.mortbay.jetty.handler.ContextHandlerCollection.handle(ContextHandlerCollection.java:230)
    at org.mortbay.jetty.handler.HandlerCollection.handle(HandlerCollection.java:114)
    at org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:152)
    at org.mortbay.jetty.Server.handle(Server.java:326)
    at org.mortbay.jetty.HttpConnection.handleRequest(HttpConnection.java:542)
    at org.mortbay.jetty.HttpConnection$RequestHandler.headerComplete(HttpConnection.java:928)
    at org.mortbay.jetty.HttpParser.parseNext(HttpParser.java:549)
    at org.mortbay.jetty.HttpParser.parseAvailable(HttpParser.java:212)
    at org.mortbay.jetty.HttpConnection.handle(HttpConnection.java:404)
    at org.mortbay.io.nio.SelectChannelEndPoint.run(SelectChannelEndPoint.java:410)
    at org.mortbay.thread.QueuedThreadPool$PoolThread.run(QueuedThreadPool.java:582)
Caused by: javax.xml.bind.UnmarshalException
 - with linked exception:
[org.xml.sax.SAXParseException; lineNumber: 1; columnNumber: 1; Content is not allowed in prolog.]
    at javax.xml.bind.helpers.AbstractUnmarshallerImpl.createUnmarshalException(AbstractUnmarshallerImpl.java:335)
    at com.sun.xml.internal.bind.v2.runtime.unmarshaller.UnmarshallerImpl.createUnmarshalException(UnmarshallerImpl.java:512)
    at com.sun.xml.internal.bind.v2.runtime.unmarshaller.UnmarshallerImpl.unmarshal0(UnmarshallerImpl.java:209)
    at com.sun.xml.internal.bind.v2.runtime.unmarshaller.UnmarshallerImpl.unmarshal(UnmarshallerImpl.java:181)
    at com.sun.xml.internal.bind.v2.runtime.unmarshaller.UnmarshallerImpl.unmarshal(UnmarshallerImpl.java:232)
    at org.glassfish.jersey.server.internal.inject.JaxbStringReaderProvider$RootElementProvider$1.fromString(JaxbStringReaderProvider.java:192)
    ... 41 more
Caused by: org.xml.sax.SAXParseException; lineNumber: 1; columnNumber: 1; Content is not allowed in prolog.
    at com.sun.org.apache.xerces.internal.util.ErrorHandlerWrapper.createSAXParseException(ErrorHandlerWrapper.java:198)
    at com.sun.org.apache.xerces.internal.util.ErrorHandlerWrapper.fatalError(ErrorHandlerWrapper.java:177)
    at com.sun.org.apache.xerces.internal.impl.XMLErrorReporter.reportError(XMLErrorReporter.java:441)
    at com.sun.org.apache.xerces.internal.impl.XMLErrorReporter.reportError(XMLErrorReporter.java:368)
    at com.sun.org.apache.xerces.internal.impl.XMLScanner.reportFatalError(XMLScanner.java:1388)
    at com.sun.org.apache.xerces.internal.impl.XMLDocumentScannerImpl$PrologDriver.next(XMLDocumentScannerImpl.java:998)
    at com.sun.org.apache.xerces.internal.impl.XMLDocumentScannerImpl.next(XMLDocumentScannerImpl.java:607)
    at com.sun.org.apache.xerces.internal.impl.XMLNSDocumentScannerImpl.next(XMLNSDocumentScannerImpl.java:116)
    at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl.scanDocument(XMLDocumentFragmentScannerImpl.java:489)
    at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(XML11Configuration.java:835)
    at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(XML11Configuration.java:764)
    at com.sun.org.apache.xerces.internal.parsers.XMLParser.parse(XMLParser.java:123)
    at com.sun.org.apache.xerces.internal.parsers.AbstractSAXParser.parse(AbstractSAXParser.java:1210)
    at com.sun.org.apache.xerces.internal.jaxp.SAXParserImpl$JAXPSAXParser.parse(SAXParserImpl.java:568)
    at com.sun.xml.internal.bind.v2.runtime.unmarshaller.UnmarshallerImpl.unmarshal0(UnmarshallerImpl.java:203)
    ... 44 more

Since it's triggered during unmarshalling by the JaxbStringReaderProvider, and it should not be the case when my generated class does not have the xml annotations. What's the best way to handle enum type method params without creating a wrapper object with string constructor for each needed enum type?

Answer 1

You should implement custom ParamConverterProvider and ParamConverter and register your implementations into JAX-RS runtime (using JAX-RS Application or web.xml). Something like:

@Provider
public class GeneratedEnumParamConverterProvider implements ParamConverterProvider {

    @Override
    public <T> ParamConverter<T> getConverter(final Class<T> rawType, final Type genericType,
                                              final Annotation[] annotations) {
        try {
            final Method fromValueMethod = rawType.getMethod("fromValue", String.class);

            return new ParamConverter<T>() {
                @Override
                public T fromString(final String value) {
                    try {
                        return rawType.cast(fromValueMethod.invoke(null, value));
                    } catch (Exception e) {
                        throw new IllegalArgumentException("Given value (" + value + ") cannot be converted to parameter of type" + rawType);
                    }
                }

                @Override
                public String toString(final T value) {
                    return value.toString();
                }
            };
        } catch (Exception e) {
            return null;
        }
    }
}

Answer 2

in org.eclipse.persistence.jaxb.JAXBContext It initiates DEFAULT_VALIDATION_EVENT_HANDER in this way:

 protected static final ValidationEventHandler DEFAULT_VALIDATION_EVENT_HANDER = new ValidationEventHandler() {
     public boolean handleEvent(ValidationEvent event) {
         return event.getSeverity() < ValidationEvent.FATAL_ERROR;
     }
 };

It raised the level to FATAL ERROR, which I think should be ERROR. So the code above can be:

 protected static final ValidationEventHandler DEFAULT_VALIDATION_EVENT_HANDER = new DefaultValidationEventHandler();

I used reflection to modify DEFAULT_VALIDATION_EVENT_HANDER it when creating server, then it can throw an exception when encountering the wrong enum string value.

The code to modify DEFAULT_VALIDATION_EVENT_HANDER in JAXBContext:

    final Field field = JAXBContext.class.getDeclaredField("DEFAULT_VALIDATION_EVENT_HANDER");
    field.setAccessible(true);

    Field modifiersField = Field.class.getDeclaredField("modifiers");
    modifiersField.setAccessible(true);
    modifiersField.setInt(field, field.getModifiers() & ~Modifier.FINAL);
    field.set(null, new DefaultValidationEventHandler());