我试图从FpML(金融产品标记语言)4.5版本生成Java类。生成了大量代码,但我无法使用它。试图序列化一个简单的文档,我得到这个:

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]

事实上,没有任何类具有@XmlRootElement注释,所以我可能做错了什么?我将xjc (JAXB 2.1)指向fpml-main-4-5。Xsd,然后包括所有类型。


当前回答

您可以使用如何在XSD中为基类型生成@XmlRootElement类中的绑定来修复此问题。

下面是Maven的一个示例

        <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>

这是装订。XJB文件内容

<?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>

其他回答

为了将其他人已经陈述或暗示的内容联系在一起,JAXB XJC决定是否将@XmlRootElement注释放在生成的类上的规则非常重要(请参阅本文)。

@XmlRootElement的存在是因为JAXB运行时需要某些信息才能封送/解封送给定对象,特别是XML元素名称和名称空间。你不能直接把任何旧对象传递给Marshaller。@XmlRootElement提供此信息。

然而,注释只是一种方便,JAXB并不需要它。另一种方法是使用JAXBElement包装器对象,它提供与@XmlRootElement相同的信息,但是以对象的形式,而不是注释的形式。

但是,JAXBElement对象构造起来很麻烦,因为您需要知道XML元素名称和名称空间,而业务逻辑通常不知道这些。

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.

如您所知,答案是使用ObjectFactory()。下面是一个为我工作的代码示例:)

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();
    }

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;
  }
}

为了解决这个问题,你应该在使用wsimport编译之前配置一个xml绑定,将generateElementProperty设置为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>

这对我们也没用。但我们确实找到了一篇被广泛引用的文章,增加了一些背景……我将在这里链接到它,以方便下一个人:http://weblogs.java.net/blog/kohsuke/archive/2006/03/why_does_jaxb_p.html