Question

如果在xml文件中找到的字段及其属性未在java类中定义，则当xml解组为java类时，我需要捕获异常。我不能完全构造xsd，其中不同的xml文件动态地放大xsd，其中包含不同的标签。这就是为什么需要捕获指定的exc，

提前致谢。

Answer 1

默认情况下，如果遇到未映射的元素/属性，JAXB (JSR-222)实现将不会抛出异常，除非已覆盖默认ValidationEventHandler或已发送Schema的实例Unmarshaller。

Java模型（根）

package forum15875338;

import javax.xml.bind.annotation.XmlRootElement;

@XmlRootElement
public class Root {

    private String foo;

    public String getFoo() {
        return foo;
    }

    public void setFoo(String foo) {
        this.foo = foo;
    }

}

<强>演示

package forum15875338;

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

public class Demo {

    private static final String XML = "<root><foo>Hello</foo><bar>World</bar></root>";

    public static void main(String[] args) throws Exception {
        JAXBContext jc = JAXBContext.newInstance(Root.class);
        Unmarshaller unmarshaller = jc.createUnmarshaller();
        Marshaller marshaller = jc.createMarshaller();
        marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true);

        // Unmarshal #1 = Default Unmarshal
        System.out.println("Unmarshal #1");
        Root root = (Root) unmarshaller.unmarshal(new StringReader(XML));
        marshaller.marshal(root, System.out);

        // Unmarshal #2 - Override Default ValidationEventHandler
        System.out.println("Unmarshal #2");
        unmarshaller.setEventHandler(new ValidationEventHandler() {
            @Override
            public boolean handleEvent(ValidationEvent event) {
                System.out.println(event.getMessage());
                return false;
            }
        });
        unmarshaller.unmarshal(new StringReader(XML));
    }

}

<强>输出

Unmarshal #1
<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<root>
    <foo>Hello</foo>
</root>
Unmarshal #2
unexpected element (uri:"", local:"bar"). Expected elements are <{}foo>
Exception in thread "main" javax.xml.bind.UnmarshalException: unexpected element (uri:"", local:"bar"). Expected elements are <{}foo>
    at com.sun.xml.bind.v2.runtime.unmarshaller.UnmarshallingContext.handleEvent(UnmarshallingContext.java:642)
    at com.sun.xml.bind.v2.runtime.unmarshaller.Loader.reportError(Loader.java:254)
    at com.sun.xml.bind.v2.runtime.unmarshaller.Loader.reportError(Loader.java:249)
    at com.sun.xml.bind.v2.runtime.unmarshaller.Loader.reportUnexpectedChildElement(Loader.java:116)
    at com.sun.xml.bind.v2.runtime.unmarshaller.Loader.childElement(Loader.java:101)
    at com.sun.xml.bind.v2.runtime.unmarshaller.StructureLoader.childElement(StructureLoader.java:243)
    at com.sun.xml.bind.v2.runtime.unmarshaller.UnmarshallingContext._startElement(UnmarshallingContext.java:478)
    at com.sun.xml.bind.v2.runtime.unmarshaller.UnmarshallingContext.startElement(UnmarshallingContext.java:459)
    at com.sun.xml.bind.v2.runtime.unmarshaller.SAXConnector.startElement(SAXConnector.java:148)
    at com.sun.org.apache.xerces.internal.parsers.AbstractSAXParser.startElement(AbstractSAXParser.java:506)
    at com.sun.org.apache.xerces.internal.impl.XMLNSDocumentScannerImpl.scanStartElement(XMLNSDocumentScannerImpl.java:376)
    at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl$FragmentContentDriver.next(XMLDocumentFragmentScannerImpl.java:2715)
    at com.sun.org.apache.xerces.internal.impl.XMLDocumentScannerImpl.next(XMLDocumentScannerImpl.java:607)
    at com.sun.org.apache.xerces.internal.impl.XMLNSDocumentScannerImpl.next(XMLNSDocumentScannerImpl.java:116)
    at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl.scanDocument(XMLDocumentFragmentScannerImpl.java:488)
    at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(XML11Configuration.java:835)
    at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(XML11Configuration.java:764)
    at com.sun.org.apache.xerces.internal.parsers.XMLParser.parse(XMLParser.java:123)
    at com.sun.org.apache.xerces.internal.parsers.AbstractSAXParser.parse(AbstractSAXParser.java:1210)
    at com.sun.org.apache.xerces.internal.jaxp.SAXParserImpl$JAXPSAXParser.parse(SAXParserImpl.java:568)
    at com.sun.xml.bind.v2.runtime.unmarshaller.UnmarshallerImpl.unmarshal0(UnmarshallerImpl.java:211)
    at com.sun.xml.bind.v2.runtime.unmarshaller.UnmarshallerImpl.unmarshal(UnmarshallerImpl.java:184)
    at javax.xml.bind.helpers.AbstractUnmarshallerImpl.unmarshal(AbstractUnmarshallerImpl.java:157)
    at javax.xml.bind.helpers.AbstractUnmarshallerImpl.unmarshal(AbstractUnmarshallerImpl.java:214)
    at forum15875338.Demo.main(Demo.java:31)

如果在java类中找不到字段，则jaxb捕获异常

1 个答案: