Question

I am using Xstream to serializing a Job object. It looks working fine.

but deserializing, I have a problem:

Exception in thread "main" com.thoughtworks.xstream.io.StreamException:  : only whitespace content allowed before start tag and not . (position: START_DOCUMENT seen .... @1:1) 
    at com.thoughtworks.xstream.io.xml.XppReader.pullNextEvent(XppReader.java:78)
    at com.thoughtworks.xstream.io.xml.AbstractPullReader.readRealEvent(AbstractPullReader.java:137)
    at com.thoughtworks.xstream.io.xml.AbstractPullReader.readEvent(AbstractPullReader.java:130)
    at com.thoughtworks.xstream.io.xml.AbstractPullReader.move(AbstractPullReader.java:109)
    at com.thoughtworks.xstream.io.xml.AbstractPullReader.moveDown(AbstractPullReader.java:94)
    at com.thoughtworks.xstream.io.xml.XppReader.<init>(XppReader.java:48)
    at com.thoughtworks.xstream.io.xml.XppDriver.createReader(XppDriver.java:44)
    at com.thoughtworks.xstream.XStream.fromXML(XStream.java:853)
    at com.thoughtworks.xstream.XStream.fromXML(XStream.java:845)

Did one of you get this problem before?

This is the way, I did for serializing:

XStream xstream = new XStream();                    
Writer writer = new FileWriter(new File("model.xml"));
writer.write(xstream.toXML(myModel));
writer.close();

I also try this as well:

XStream xstream = new XStream();                    
OutputStream out = new FileOutputStream("model.xml");
xstream.toXML(myModel, out);

For deserializing, I did it like this:

XStream xstream = new XStream();

xstream.fromXML("model.xml");

XML structure:

<projectCar.CarImpl> 
   <CarModel reference="../.."></CarModel>
</projectCar.CarImpl> 

If yes, I would like to hear. Thanks in advance.

Answer 1

fromXML does not take a filename, try:

File xmlFile = new File("model.xml");
xstream.fromXML(new FileInputStream(xmlFile));

to read the file contents as a String.

Also the fieldnames ‘id’ and ‘reference’ happen to be ‘system attributes’ in XStream. Using the following code:

CarImpl myModel = new CarImpl();

File xmlFile = new File("model.xml");

XStream xstream = new XStream();
xstream.useAttributeFor(String.class);
xstream.useAttributeFor(Integer.class);

Writer writer = new FileWriter(xmlFile);        
writer.write(xstream.toXML(myModel));
writer.close();

CarImpl fromXML = (CarImpl) xstream.fromXML(new FileInputStream(xmlFile));
System.out.println(fromXML);

unmarshalling fails if the fields are called ‘id’ and ‘reference’, but succeeds otherwise. See XStream FAQ

Take a look at the new method ‘aliasForSystemAttribute’ for a possible solution.