关于 jaxb:xs:int 对于十进制值未编组为 null


xs:int unmarshalled to null for decimal values

我遇到了一个与基于 JAX-WS 的 WebService 中的解组过程相关的问题。在 WSDL 文件中有一个元素定义为

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    <element name="quantity" nillable="true" type="int" />

在相关的JAVA类中定义为：

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   @XmlElement(name ="Quantity", required = true, type = Integer.class, nillable = true)
   protected Integer quantity;

当此元素的 XML 值是十进制数 (3.4) 的表示形式时，该元素将被解组为空整数。不会生成 SOAPFault，并且无法在 WebService 中区分十进制值和空值。
这可能是 JAXB 实现中的缺陷还是我做错了什么？

Could it be a defect in JAXB implementation or I'm doing something
wrong?

这不是 JAXB (JSR-222) 实现中的缺陷。这是将 JAX-WS 配置为使用 JAXB 的结果。我将在下面用一个例子来演示。

根

下面是一个域对象，其字段与您问题中的字段相匹配。我已经从 @XmlElement 注释中删除了 type=Integer.class，因为它是多余的。

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import javax.xml.bind.annotation.*;

@XmlRootElement
@XmlAccessorType(XmlAccessType.FIELD)
public class Root {

    @XmlElement(name ="Quantity", required = true, nillable = true)
    protected Integer quantity;

}

演示

JAXB 提供了在 Unmarshaller 上设置 ValidationEventHandler 的能力，让您可以控制如何处理解组错误。

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import java.io.StringReader;
import javax.xml.bind.*;

public class Demo {

    public static void main(String[] args) throws Exception {
        JAXBContext jc = JAXBContext.newInstance(Root.class);

        Unmarshaller unmarshaller = jc.createUnmarshaller();
        unmarshaller.setEventHandler(new ValidationEventHandler() {

            @Override
            public boolean handleEvent(ValidationEvent event) {
                System.out.println(event.getMessage());
                return true;
            }
        });

        StringReader xml = new StringReader("<root><Quantity>3.4</Quantity></root>");
        Root root = (Root) unmarshaller.unmarshal(xml);

        Marshaller marshaller = jc.createMarshaller();
        marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true);
        marshaller.marshal(root, System.out);
    }

}

输出

在专家组中，我们认为无效元素数据很常见，并且每次遇到这种情况时 JAXB 都不应失败，但您可以看到引发了 ValidationEvent。

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Not a number: 3.4
<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<root>
    <Quantity xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:nil="true"/>
</root>

更新演示

如果我们更新 ValidationEventHandler 以表明我们不希望在引发 ValidationEvent 时继续 unmarshal，我们可以进行以下更改。

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        @Override
        public boolean handleEvent(ValidationEvent event) {
            System.out.println(event.getMessage());
            return false;
        }

更新的输出

现在出现以下输出。

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Not a number: 3.4
Exception in thread"main" javax.xml.bind.UnmarshalException: Not a number: 3.4
 - with linked exception:
[java.lang.NumberFormatException: Not a number: 3.4]
    at com.sun.xml.internal.bind.v2.runtime.unmarshaller.UnmarshallingContext.handleEvent(UnmarshallingContext.java:647)
    at com.sun.xml.internal.bind.v2.runtime.unmarshaller.UnmarshallingContext.handleError(UnmarshallingContext.java:676)
    at com.sun.xml.internal.bind.v2.runtime.unmarshaller.UnmarshallingContext.handleError(UnmarshallingContext.java:672)
    at com.sun.xml.internal.bind.v2.runtime.unmarshaller.Loader.handleParseConversionException(Loader.java:256)
    at com.sun.xml.internal.bind.v2.runtime.unmarshaller.LeafPropertyLoader.text(LeafPropertyLoader.java:54)
    at com.sun.xml.internal.bind.v2.runtime.unmarshaller.UnmarshallingContext.text(UnmarshallingContext.java:499)
    at com.sun.xml.internal.bind.v2.runtime.unmarshaller.SAXConnector.processText(SAXConnector.java:166)
    at com.sun.xml.internal.bind.v2.runtime.unmarshaller.SAXConnector.endElement(SAXConnector.java:139)
    at com.sun.org.apache.xerces.internal.parsers.AbstractSAXParser.endElement(AbstractSAXParser.java:606)
    at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl.scanEndElement(XMLDocumentFragmentScannerImpl.java:1742)
    at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl$FragmentContentDriver.next(XMLDocumentFragmentScannerImpl.java:2900)
    at com.sun.org.apache.xerces.internal.impl.XMLDocumentScannerImpl.next(XMLDocumentScannerImpl.java:607)
    at com.sun.org.apache.xerces.internal.impl.XMLNSDocumentScannerImpl.next(XMLNSDocumentScannerImpl.java:116)
    at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl.scanDocument(XMLDocumentFragmentScannerImpl.java:489)
    at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(XML11Configuration.java:835)
    at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(XML11Configuration.java:764)
    at com.sun.org.apache.xerces.internal.parsers.XMLParser.parse(XMLParser.java:123)
    at com.sun.org.apache.xerces.internal.parsers.AbstractSAXParser.parse(AbstractSAXParser.java:1210)
    at com.sun.org.apache.xerces.internal.jaxp.SAXParserImpl$JAXPSAXParser.parse(SAXParserImpl.java:568)
    at com.sun.xml.internal.bind.v2.runtime.unmarshaller.UnmarshallerImpl.unmarshal0(UnmarshallerImpl.java:203)
    at com.sun.xml.internal.bind.v2.runtime.unmarshaller.UnmarshallerImpl.unmarshal(UnmarshallerImpl.java:175)
    at javax.xml.bind.helpers.AbstractUnmarshallerImpl.unmarshal(AbstractUnmarshallerImpl.java:157)
    at javax.xml.bind.helpers.AbstractUnmarshallerImpl.unmarshal(AbstractUnmarshallerImpl.java:214)
    at forum14741140.Demo.main(Demo.java:22)
Caused by: java.lang.NumberFormatException: Not a number: 3.4
    at com.sun.xml.internal.bind.DatatypeConverterImpl._parseInt(DatatypeConverterImpl.java:101)
    at com.sun.xml.internal.bind.v2.model.impl.RuntimeBuiltinLeafInfoImpl$17.parse(RuntimeBuiltinLeafInfoImpl.java:713)
    at com.sun.xml.internal.bind.v2.model.impl.RuntimeBuiltinLeafInfoImpl$17.parse(RuntimeBuiltinLeafInfoImpl.java:711)
    at com.sun.xml.internal.bind.v2.runtime.reflect.TransducedAccessor$CompositeTransducedAccessorImpl.parse(TransducedAccessor.java:232)
    at com.sun.xml.internal.bind.v2.runtime.unmarshaller.LeafPropertyLoader.text(LeafPropertyLoader.java:50)
    ... 19 more
相关讨论

我回答了这个问题：https://stackoverflow.com/a/30617814/3632201

上周我一直在努力解决这个问题，最后我找到了一个可行的解决方案。诀窍是 JAXB 在使用 @XmlRootElement 注释的对象中查找方法 beforeUnmarshal 和 afterUnmarshal。

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..
@XmlRootElement(name="MSEPObtenerPolizaFechaDTO")
@XmlAccessorType(XmlAccessType.FIELD)

public class MSEPObtenerPolizaFechaDTO implements Serializable {
..

public void beforeUnmarshal(Unmarshaller unmarshaller, Object parent) throws JAXBException, IOException, SAXException {
        unmarshaller.setSchema(Utils.getSchemaFromContext(this.getClass()));
        unmarshaller.setEventHandler(new CustomEventHandler());
  }

  public void afterUnmarshal(Unmarshaller unmarshaller, Object parent) throws JAXBException {
        unmarshaller.setSchema(null);
        unmarshaller.setEventHandler(null);
  }

使用这个 ValidationEventHandler:

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public class CustomEventHandler implements ValidationEventHandler{

      @Override
      public boolean handleEvent(ValidationEvent event) {
            if (event.getSeverity() == event.ERROR ||
                        event.getSeverity() == event.FATAL_ERROR)
            {
                  ValidationEventLocator locator = event.getLocator();
                  throw new RuntimeException(event.getMessage(), event.getLinkedException());
            }
            return true;
      }
}

}

这是在你的 Utility 类中创建的 getSchemaFromContext 方法：

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  @SuppressWarnings("unchecked")
  public static Schema getSchemaFromContext(Class clazz) throws JAXBException, IOException, SAXException{
        JAXBContext jc = JAXBContext.newInstance(clazz);
        final List<ByteArrayOutputStream> outs = new ArrayList<ByteArrayOutputStream>();
        jc.generateSchema(new SchemaOutputResolver(){
              @Override
              public Result createOutput(String namespaceUri,
                         String suggestedFileName) throws IOException {
              ByteArrayOutputStream out = new ByteArrayOutputStream();
              outs.add(out);
              StreamResult streamResult = new StreamResult(out);
              streamResult.setSystemId("");
              return streamResult;
              }
        });
        StreamSource[] sources = new StreamSource[outs.size()];
        for (int i = 0; i < outs.size(); i++) {
              ByteArrayOutputStream out = outs.get(i);
              sources[i] = new StreamSource(new ByteArrayInputStream(out.toByteArray()),"");
        }
        SchemaFactory sf = SchemaFactory.newInstance(XMLConstants.W3C_XML_SCHEMA_NS_URI);
        return sf.newSchema(sources);
  }