jaxb catch exception if field is not found in java class

Question

I need to catch the exception when an xml is unmarshalling to a java class if a field and its attribute(s) found in xml file are not defined in java class. I am not able to construct the xsd completely where different xml files dynamically enlarge the xsd, which has different tags in it. That's why in need to catch specified exc,

Thanks in advance.

Answer 1

By default a JAXB (JSR-222) implementation will not throw an exception if an unmapped element/attribute has been encountered unless the default ValidationEventHandler has been overridden or an instance of Schema has been sent on the Unmarshaller.

Java Model (Root)

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;
    }

}

Demo

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));
    }

}

Output

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)