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stax

Can I "jump around" in an XMLStreamWriter's output stream

I just have this question around the Stax XMLStreamWriter. Best explained by example:

Say I need to produce a document somehow like this:

<buddies>
 <buddies name="tim"/>
 <buddies name="toady"/>
</buddies>

, where the tim and toady guys are created by some callback that receives the XMLStreamWriter as an argument. 

writer.writeElement("buddies");
 callback1.writeBuddies(writer);
 callback2.writeBuddies(writer);
write.writeEndElement();

Now the thing is, the whole document must conform to a schema that states: If there's a <buddies> element, there must be at least one <buddy> inside, so if none of my callbacks write anything on the stream I'd have an empty element which is invalid. Question is: Can I delay the writeElement("buddies") somehow like this:

// Pseudocode
Mark mark = writer.getPos()
boolean written = callback1.writeBuddies(writer)
written |= callback2.writeBuddies(writer)
if (written){
  writer.writeStartElement(mark, "buddies") // write at mark
  writer.writeStopElement() // write at the end of stream
}

Or am I completely off the track?

Solution

  • StAX is a forward only streaming API. To achieve what you are asking is a potential requirement for DOM parser where you construct the node "buddies" separately and attach it to the main document if it is not empty.