Handling invalid enum values while doing JAXB Unmarshalling - web-services

Question

My Jaxb has created a Enum class based on the XML schema set up.
**enum Fruit {
APPLE,ORANGE;
}**
I am using a SOAP UI to check my web service. Since it is a free form entry, if i give a wrong fruit say "Guva" then instead of throwing an exception it is returning it as null after doing the UnMarshalling.
How can i avoid this? Should i use custom enum class instead of JAXB generated one. Please give some example. i.e.
regards
sri

Answer 1

Note: I'm the EclipseLink JAXB (MOXy) lead and a member of the JAXB (JSR-222) expert group.
By default your JAXB (JSR-222) implementation will not fail on any conversion exceptions. If you are using the JAXB APIs to do the unmarshalling then you can set a ValidationEventHandler to catch any problems. Below is an example.
Root
package forum12147306;
import javax.xml.bind.annotation.XmlRootElement;
#XmlRootElement
public class Root {
private int number;
private Fruit fruit;
public int getNumber() {
return number;
}
public void setNumber(int number) {
this.number = number;
}
public Fruit getFruit() {
return fruit;
}
public void setFruit(Fruit fruit) {
this.fruit = fruit;
}
}
Fruit
package forum12147306;
public enum Fruit {
APPLE,
ORANGE;
}
Demo
package forum12147306;
import java.io.StringReader;
import javax.xml.bind.*;
public class Demo {
private static final String XML = "<root><number>ABC</number><fruit>Guva</fruit></root>";
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 validationEvent) {
System.out.println(validationEvent.getMessage());
//validationEvent.getLinkedException().printStackTrace();
return true;
}
});
Root root = (Root) unmarshaller.unmarshal(new StringReader(XML));
}
}
JAXB REFERENCE IMPLEMENTATION
Unfortunately there appears to be a bug in the JAXB RI as a validation event is not being through for the invalid enum value.
Not a number: ABC
Work Around
Write your own XmlAdapter to handle to conversion to/from the Fruit enum:
FruitAdapter
package forum12147306;
import javax.xml.bind.JAXBException;
import javax.xml.bind.annotation.adapters.XmlAdapter;
public class FruitAdapter extends XmlAdapter<String, Fruit> {
#Override
public String marshal(Fruit fruit) throws Exception {
return fruit.name();
}
#Override
public Fruit unmarshal(String string) throws Exception {
try {
return Fruit.valueOf(string);
} catch(Exception e) {
throw new JAXBException(e);
}
}
}
Fruit
Use the #XmlJavaTypeAdapter annotation to associate the XmlAdapter with the Fruit enumb.
package forum12147306;
import javax.xml.bind.annotation.adapters.XmlJavaTypeAdapter;
#XmlJavaTypeAdapter(FruitAdapter.class)
public enum Fruit {
APPLE,
ORANGE;
}
New Output
Not a number: ABC
javax.xml.bind.JAXBException
- with linked exception:
[java.lang.IllegalArgumentException: No enum const class forum12147306.Fruit.Guva]
EclipseLink JAXB (MOXy)
Using MOXy both validation events are thrown. To specify MOXy as your JAXB provider see: http://blog.bdoughan.com/2011/05/specifying-eclipselink-moxy-as-your.html.
Exception Description: The object [ABC], of class [class java.lang.String], from mapping [org.eclipse.persistence.oxm.mappings.XMLDirectMapping[number-->number/text()]] with descriptor [XMLDescriptor(forum12147306.Root --> [DatabaseTable(root)])], could not be converted to [class java.lang.Integer].
Internal Exception: java.lang.NumberFormatException: For input string: "ABC"
Exception Description: No conversion value provided for the value [Guva] in field [fruit/text()].
Mapping: org.eclipse.persistence.oxm.mappings.XMLDirectMapping[fruit-->fruit/text()]
Descriptor: XMLDescriptor(forum12147306.Root --> [DatabaseTable(root)])

Answer 2

Short answer based on original reply. You need to do 2 things
implement custom adapter to raise and exception
add event handler to fail unmarshalling
Fruit.java defines and uses the adapter
package forum12147306;
import javax.xml.bind.annotation.adapters.XmlJavaTypeAdapter;
#XmlJavaTypeAdapter(FruitAdapter.class)
public enum Fruit {
APPLE,
ORANGE;
}
class FruitAdapter extends XmlAdapter<String, Fruit> {
#Override
public String marshal(Fruit fruit) throws Exception {
return fruit.name();
}
#Override
public Fruit unmarshal(String string) throws Exception {
try {
return Fruit.valueOf(string);
} catch(Exception e) {
throw new JAXBException(e);
}
}
}
The event handler for unmarshaller that fails parsing on error - i.e it returns false (you might need to decide when to fail and when not to fail)
JAXBContext jc = JAXBContext.newInstance(Root.class);
Unmarshaller unmarshaller = jc.createUnmarshaller();
unmarshaller.setEventHandler(new ValidationEventHandler() {
#Override
public boolean handleEvent(ValidationEvent validationEvent) {
return false;
}
});

Answer 3

An alternative consists in generating XSD schemas as presented in here: how can i unmarshall in jaxb and enjoy the schema validation without using an explicit schema file.
Here is the snippet I stole from dolbysurnd:
import java.io.IOException;
import java.io.Reader;
import java.util.ArrayList;
import javax.xml.bind.JAXBContext;
import javax.xml.bind.JAXBException;
import javax.xml.bind.SchemaOutputResolver;
import javax.xml.bind.Unmarshaller;
import javax.xml.transform.Result;
import javax.xml.transform.dom.DOMResult;
import javax.xml.transform.dom.DOMSource;
import javax.xml.validation.Schema;
import javax.xml.validation.SchemaFactory;
import org.xml.sax.SAXException;
private static List<DOMResult> generateJaxbSchemas(JAXBContext context) throws IOException {
final List<DOMResult> domResultList = new ArrayList<>();
context.generateSchema(new SchemaOutputResolver() {
#Override
public Result createOutput(String ns, String file) throws IOException {
DOMResult domResult = new DOMResult();
domResult.setSystemId(file);
domResultList.add(domResult);
return domResult;
}
});
return domResultList;
}
private static Unmarshaller createUnmarshaller(JAXBContext context) throws SAXException, IOException, JAXBException {
Unmarshaller unmarshaller = context.createUnmarshaller();
List<DOMSource> domSourceList = new ArrayList<>();
for (DOMResult domResult : generateJaxbSchemas(context)) {
domSourceList.add(new DOMSource(domResult.getNode()));
}
SchemaFactory schemaFactory = SchemaFactory.newInstance("http://www.w3.org/2001/XMLSchema");
Schema schema = schemaFactory.newSchema(domSourceList.toArray(new DOMSource[0]));
unmarshaller.setSchema(schema);
return unmarshaller;
}
public void unmarshal(JAXBContext context, Reader reader) throws JAXBException, SAXException, IOException {
Unmarshaller unmarshaller = createUnmarshaller(context);
Object result = unmarshaller.unmarshal(reader);
}