JAXB marshals XML differently to OutputStream vs. StringWriter
- by Andy
I apologize if this has been answered, but the search terms I have been using (i.e. JAXB @XmlAttribute condensed or JAXB XML marshal to String different results) aren't coming up with anything.
I am using JAXB to un/marshal objects annotated with @XmlElement and @XmlAttribute annotations. I have a formatter class which provides two methods -- one wraps the marshal method and accepts the object to marshal and an OutputStream, the other just accepts the object and returns the XML output as a String. Unfortunately, these methods do not provide the same output for the same objects. When marshaling to a file, simple object fields internally marked with @XmlAttribute are printed as:
<element value="VALUE"></element>
while when marshaling to a String, they are:
<element value="VALUE"/>
I would prefer the second format for both cases, but I am curious as to how to control the difference, and would settle for them being the same regardless. I even created one static marshaller that both methods use to eliminate different instance values. The formatting code follows:
/** Marker interface for classes which are listed in jaxb.index */
public interface Marshalable {}
/** Local exception class */
public class XMLMarshalException extends BaseException {}
/** Class which un/marshals objects to XML */
public class XmlFormatter {
private static Marshaller marshaller = null;
private static Unmarshaller unmarshaller = null;
static {
try {
JAXBContext context = JAXBContext.newInstance("path.to.package");
marshaller = context.createMarshaller();
marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true);
marshaller.setProperty(Marshaller.JAXB_ENCODING, "UTF-8");
unmarshaller = context.createUnmarshaller();
} catch (JAXBException e) {
throw new RuntimeException("There was a problem creating a JAXBContext object for formatting the object to XML.");
}
}
public void marshal(Marshalable obj, OutputStream os) throws XMLMarshalException {
try {
marshaller.marshal(obj, os);
} catch (JAXBException jaxbe) {
throw new XMLMarshalException(jaxbe);
}
}
public String marshalToString(Marshalable obj) throws XMLMarshalException {
try {
StringWriter sw = new StringWriter();
marshaller.marshal(obj, sw);
} catch (JAXBException jaxbe) {
throw new XMLMarshalException(jaxbe);
}
}
}
/** Example data */
@XmlType
@XmlAccessorType(XmlAccessType.FIELD)
public class Data {
@XmlAttribute(name = value)
private String internalString;
}
/** Example POJO */
@XmlType
@XmlRootElement(namespace = "project/schema")
@XmlAccessorType(XmlAccessType.FIELD)
public class Container implements Marshalable {
@XmlElement(required = false, nillable = true)
private int number;
@XmlElement(required = false, nillable = true)
private String word;
@XmlElement(required = false, nillable = true)
private Data data;
}
The result of calling marshal(container, new FileOutputStream("output.xml")) and marshalToString(container) are as follows:
Output to file
<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<ns2:container xmlns:ns2="project/schema">
<number>1</number>
<word>stackoverflow</word>
<data value="This is internal"></data>
</ns2:container>
and
Output to String
<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<ns2:container xmlns:ns2="project/schema">
<number>1</number>
<word>stackoverflow</word>
<data value="This is internal"/>
</ns2:container>
