No @XmlRootElement generated by JAXB

Question

I'm trying to generate Java classes from the FpML (Finanial Products Markup Language) version 4.5. A ton of code is generated, but I cannot use it. Trying to serialize a simple document I get this:

javax.xml.bind.MarshalException
  - with linked exception: [com.sun.istack.SAXException2: unable
  to marshal type
  "org.fpml._2008.fpml_4_5.PositionReport"
  as an element because it is missing an
  @XmlRootElement annotation]

In fact no classses have the @XmlRootElement annotation, so what can I be doing wrong?. I'm pointing xjc (JAXB 2.1) to fpml-main-4-5.xsd, which then includes all types.

Answer 1

To tie together what others have already stated or hinted at, the rules by which JAXB XJC decides whether or not to put the @XmlRootElement annotation on a generated class are non trivial (see this article).

@XmlRootElement exists because the JAXB runtime requires certain information in order to marshal/unmarshal a given object, specifically the XML element name and namespace. You can't just pass any old object to the Marshaller. @XmlRootElement provides this information.

The annotation is just a convenience, however - JAXB does not require it. The alternative to is to use JAXBElement wrapper objects, which provide the same information as @XmlRootElement, but in the form of an object, rather than an annotation.

However, JAXBElement objects are awkward to construct, since you need to know the XML element name and namespace, which business logic usually doesn't.

Thankfully, when XJC generates a class model, it also generates a class called ObjectFactory. This is partly there for backwards compatibility with JAXB v1, but it's also there as a place for XJC to put generated factory methods which create JAXBElement wrappers around your own objects. It handles the XML name and namespace for you, so you don't need to worry about it. You just need to look through the ObjectFactory methods (and for large schema, there can be hundreds of them) to find the one you need.

Answer 2

This is mentioned at the bottom of the blog post already linked above but this works like a treat for me:

Marshaller marshaller = jc.createMarshaller();
marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, Boolean.TRUE);
marshaller.marshal(new JAXBElement<MyClass>(new QName("uri","local"), MyClass.class, myClassInstance), System.out);

Answer 3

As hinted at in one of the above answers, you won't get an XMLRootElement on your root element if in the XSD its type is defined as a named type, since that named type could be used elsewhere in your XSD. Try mking it an anonymous type, i.e. instead of:

<xsd:element name="myRootElement" type="MyRootElementType" />

<xsd:complexType name="MyRootElementType">
...
</xsd:complexType>

you would have:

<xsd:element name="myRootElement">
    <xsd:complexType>
    ...
    <xsd:complexType>
</xsd:element>

Answer 4

@XmlRootElement is not needed for unmarshalling - if one uses the 2 parameter form of Unmarshaller#unmarshall.

So, if instead of doing:

UserType user = (UserType) unmarshaller.unmarshal(new StringReader(responseString));

one should do:

JAXBElement<UserType> userElement = unmarshaller.unmarshal(someSource, UserType.class);
UserType user = userElement.getValue();

The latter code will not require @XmlRootElement annotation at UserType class level.

Answer 5

Joe's answer (Joe Jun 26 '09 at 17:26) does it for me. The simple answer is that absence of an @XmlRootElement annotation is no problem if you marshal a JAXBElement. The thing that confused me is the generated ObjectFactory has 2 createMyRootElement methods - the first takes no parameters and gives the unwrapped object, the second takes the unwrapped object and returns it wrapped in a JAXBElement, and marshalling that JAXBElement works fine. Here's the basic code I used (I'm new to this, so apologies if the code's not formatted correctly in this reply), largely cribbed from link text:

ObjectFactory objFactory = new ObjectFactory();
MyRootElement root = objFactory.createMyRootElement();
...
// Set root properties
...
if (!writeDocument(objFactory.createMyRootElement(root), output)) {
    System.err.println("Failed to marshal XML document");
}
...

private boolean writeDocument(JAXBElement document, OutputStream output) {

  Class<?> clazz = document.getValue().getClass();
  try {
    JAXBContext context =
        JAXBContext.newInstance(clazz.getPackage().getName());
    Marshaller m = context.createMarshaller();
    m.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, Boolean.TRUE);
    m.marshal(document, output);
    return true;

  } catch (JAXBException e) {
    e.printStackTrace(System.err);
    return false;
  }
}

Answer 6

You can fix this issue using the binding from How to generate @XmlRootElement Classes for Base Types in XSD?.

Here is an example with Maven

        <plugin>
            <groupId>org.codehaus.mojo</groupId>
            <artifactId>jaxb2-maven-plugin</artifactId>
            <version>1.3.1</version>
            <executions>
                <execution>
                    <id>xjc</id>
                    <goals>
                        <goal>xjc</goal>
                    </goals>
                </execution>
            </executions>
            <configuration>
                <schemaDirectory>src/main/resources/xsd</schemaDirectory>
                <packageName>com.mycompany.schemas</packageName>
                <bindingFiles>bindings.xjb</bindingFiles>
                <extension>true</extension>
            </configuration>
        </plugin>

Here is the binding.xjb file content

<?xml version="1.0"?>
<jxb:bindings version="1.0" xmlns:jxb="http://java.sun.com/xml/ns/jaxb"
              xmlns:xjc= "http://java.sun.com/xml/ns/jaxb/xjc"
              jxb:extensionBindingPrefixes="xjc" xmlns:xs="http://www.w3.org/2001/XMLSchema">
    <jxb:bindings schemaLocation="path/to/myschema.xsd" node="/xs:schema">
        <jxb:globalBindings>
            <xjc:simple/>
        </jxb:globalBindings>
    </jxb:bindings>
</jxb:bindings>

Answer 7

As you know the answer is to use the ObjectFactory(). Here is a sample of the code that worked for me :)

ObjectFactory myRootFactory = new ObjectFactory();

MyRootType myRootType = myRootFactory.createMyRootType();

try {

        File file = new File("./file.xml");
        JAXBContext jaxbContext = JAXBContext.newInstance(MyRoot.class);
        Marshaller jaxbMarshaller = jaxbContext.createMarshaller();

        //output pretty printed
        jaxbMarshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true);

        JABXElement<MyRootType> myRootElement = myRootFactory.createMyRoot(myRootType);

        jaxbMarshaller.marshal(myRootElement, file);
        jaxbMarshaller.marshal(myRootElement, System.out);

    } catch (JAXBException e) {
        e.printStackTrace();
    }

Answer 8

After sruggling for two days I found the solution for the problem.You can use the ObjectFactory class to workaround for the classes which doesn't have the @XmlRootElement. ObjectFactory has overloaded methods to wrap it around the JAXBElement.

Method:1 does the simple creation of the object.

Method:2 will wrap the object with @JAXBElement.

Always use Method:2 to avoid javax.xml.bind.MarshalException - with linked exception missing an @XmlRootElement annotation.

Please find the sample code below

Method:1 does the simple creation of the object

public GetCountry createGetCountry() {
        return new GetCountry();
    }

Method:2 will wrap the object with @JAXBElement.

 @XmlElementDecl(namespace = "my/name/space", name = "getCountry")
 public JAXBElement<GetCountry> createGetCountry(GetCountry value) {
        return new JAXBElement<GetCountry>(_GetCountry_QNAME, GetCountry.class, null, value);
    }

Working code sample:

ClassPathXmlApplicationContext context = new ClassPathXmlApplicationContext("applicationContext.xml");
WebServiceTemplate springWSTemplate = context.getBean(WebServiceTemplate.class);

GetCountry request = new GetCountry();
request.setGuid("test_guid");

JAXBElement<GetCountryResponse> jaxbResponse = (JAXBElement<GetCountryResponse>)springWSTemplate .marshalSendAndReceive(new ObjectFactory().createGetCountry(request));

GetCountryResponse response = jaxbResponse.getValue();

Answer 9

In case my experience of this problem gives someone a Eureka! moment.. I'll add the following:

I was also getting this problem, when using an xsd file that I had generated using IntelliJ's "Generate xsd from Instance document" menu option.

When I accepted all the defaults of this tool, it generated an xsd file that when used with jaxb, generated java files with no @XmlRootElement. At runtime when I tried to marshal I got the same exception as discussed in this question.

I went back to the IntellJ tool, and saw the default option in the "Desgin Type" drop down (which of course I didn't understand.. and still don't if I'm honest) was:

Desgin Type:

"local elements/Global complex types"

I changed this to

"local elements/types"

, now it generated a (substantially) different xsd, that produced the @XmlRootElement when used with jaxb. Can't say I understand the in's and out's of it, but it worked for me.

Answer 10

It's not working for us either. But we did find a widely-quoted article that adds SOME background... I'll link to it here for the sake of the next person: http://weblogs.java.net/blog/kohsuke/archive/2006/03/why_does_jaxb_p.html

Answer 11

With a Maven build, you can add the @XmlRootElement annotation

with the "jaxb2-basics-annotate" plug-in.

See more information : see

Configure Maven to generate classes from XML Schema using JAXB

and JAXB XJC code generation

Answer 12

JAXBElement wrappers works for cases where no @XmlRootElement is generated by JAXB. These wrappers are available in ObjectFactory class generated by maven-jaxb2-plugin. For eg:

     public class HelloWorldEndpoint {
        @PayloadRoot(namespace = NAMESPACE_URI, localPart = "person")
        @ResponsePayload
        public JAXBElement<Greeting> sayHello(@RequestPayload JAXBElement<Person> request) {

        Person person = request.getValue();

        String greeting = "Hello " + person.getFirstName() + " " + person.getLastName() + "!";

        Greeting greet = new Greeting();
        greet.setGreeting(greeting);

        ObjectFactory factory = new ObjectFactory();
        JAXBElement<Greeting> response = factory.createGreeting(greet);
        return response;
      }
 }

Answer 13

Did you try to change your xsd like this?

<!-- create-logical-system -->
<xs:element name="methodCall">
  <xs:complexType>
    ...
  </xs:complexType>
</xs:element>

Answer 14

The topic is quite old but still relevant in enterprise business contexts. I tried to avoid to touch the xsds in order to easily update them in the future. Here are my solutions..

1. Mostly xjc:simple is sufficient

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<jxb:bindings version="2.0" xmlns:jxb="http://java.sun.com/xml/ns/jaxb"
    xmlns:xjc="http://java.sun.com/xml/ns/jaxb/xjc"
    jxb:extensionBindingPrefixes="xjc">

    <jxb:globalBindings>
        <xjc:simple/> <!-- adds @XmlRootElement annotations -->
    </jxb:globalBindings>

</jxb:bindings>

It will mostly create XmlRootElements for importing xsd definitions.

2. Divide your jaxb2-maven-plugin executions

I have encountered that it makes a huge difference if you try to generate classes from multiple xsd definitions instead of a execution definition per xsd.

So if you have a definition with multiple <source>'s, than just try to split them:

          <execution>
            <id>xjc-schema-1</id>
            <goals>
              <goal>xjc</goal>
            </goals>
            <configuration>
              <xjbSources>
                <xjbSource>src/main/resources/xsd/binding.xjb</xjbSource>
              </xjbSources>
              <sources>
                <source>src/main/resources/xsd/definition1/</source>
              </sources>
              <clearOutputDir>false</clearOutputDir>
            </configuration>
          </execution>

          <execution>
            <id>xjc-schema-2</id>
            <goals>
              <goal>xjc</goal>
            </goals>
            <configuration>
              <xjbSources>
                <xjbSource>src/main/resources/xsd/binding.xjb</xjbSource>
              </xjbSources>
              <sources>
                <source>src/main/resources/xsd/definition2/</source>
              </sources>
              <clearOutputDir>false</clearOutputDir>
            </configuration>
          </execution>

The generator will not catch the fact that one class might be sufficient and therefore create custom classes per execution. And thats exactly what I need ;).

Answer 15

To soluction it you should configure a xml binding before to compile with wsimport, setting generateElementProperty as false.

     <jaxws:bindings wsdlLocation="LOCATION_OF_WSDL"
      xmlns:jaxws="http://java.sun.com/xml/ns/jaxws"
      xmlns:xjc="http://java.sun.com/xml/ns/jaxb/xjc" 
      xmlns:xs="http://www.w3.org/2001/XMLSchema"
      xmlns:jxb="http://java.sun.com/xml/ns/jaxb"
      xmlns:wsdl="http://schemas.xmlsoap.org/wsdl/">
         <jaxws:enableWrapperStyle>false</jaxws:enableWrapperStyle>
    <jaxws:bindings  node="wsdl:definitions/wsdl:types/xs:schema[@targetNamespace='NAMESPACE_OF_WSDL']">
      <jxb:globalBindings xmlns:jxb="http://java.sun.com/xml/ns/jaxb" xmlns:xs="http://www.w3.org/2001/XMLSchema">
            <xjc:generateElementProperty>false</xjc:generateElementProperty> 
      </jxb:globalBindings>
  </jaxws:bindings>
</jaxws:bindings>

Answer 16

I just was struggling for a while with the same problem and just want to post my final result which works fine for me. So the base problems have been:

• I have to generate xml strings from JAXB class instances with have no XmlRootElement annotations
• The classes need additional classes to be bound for the marshalling process

The following class works fine for this problem:

public class Object2XmlConverter {

    public static <T> String convertToString(final T jaxbInstance, final Class<?>... additionalClasses)
            throws JAXBException {
        final Class<T> clazz = (Class<T>) jaxbInstance.getClass();

        final JAXBContext jaxbContext;
        if (additionalClasses.length > 0) {
            // this path is only necessary if you need additional classes to be bound
            jaxbContext = JAXBContext.newInstance(addClassesToBeBound(clazz, additionalClasses));
        } else {
            jaxbContext = JAXBContext.newInstance(clazz);
        }

        final QName qname = new QName("", jaxbInstance.getClass().getSimpleName());
        final JAXBElement<T> jaxbElement = new JAXBElement<T>(qname, clazz, null, jaxbInstance);

        final Marshaller jaxbMarshaller = jaxbContext.createMarshaller();
        jaxbMarshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, Boolean.TRUE);

        final StringWriter stringWriter = new StringWriter();
        jaxbMarshaller.marshal(jaxbElement, stringWriter);
        return stringWriter.toString();
    }

    private static <T> Class<?>[] addClassesToBeBound(final Class<T> clazz, final Class<?>[] additionalClasses) {
        final Class<?>[] classArray = new Class<?>[additionalClasses.length + 1];
        for (int i = 0; i < additionalClasses.length; i++) {
            classArray[i] = additionalClasses[i];
        }
        classArray[classArray.length - 1] = clazz;
        return classArray;
    }

    public static void main(final String[] args) throws Exception {
        final Ns1TargetHeaderTyp dataTyp = ...;
        System.out.println(convertToString(dataTyp));
    }
}