How can one force a specific serialization order with the SimpleXML Framework?

Question

I am still experimenting with the SimpleXML framework. As a first step I am parsing a larger XML file and then immediately emitting it as XML again, i.e. my test-program so far looks like:

Persister serializer = new Persister(new TypeMatcher()); 
File source = new File(filenameIn);
List myList = serializer.read(List.class, source);
serializer.write(myList, outfile);

This works all fine, however, what I noticed is, that the fields of the List are emitted in the wrong order!

The schema that my List has to follow reads:

<xs:element name="list">
    <xs:complexType>
        <xs:sequence>
            <xs:element name="properties" type="Properties" maxOccurs="1" minOccurs="1" />
            <xs:element name="columns" type="Columns" maxOccurs="unbounded" minOccurs="1" />
            <xs:element name="items" type="Items" maxOccurs="unbounded" minOccurs="0" />
        </xs:sequence>
    </xs:complexType>
</xs:element>

When the list is written, however, the sequence that I get is:

<list>
   <items>
      ...
   </items>
   <properties ...>
    ...
   </properties>
   <columns>
    ...
   </columns>
</list>

i.e. the items, which should come last, are emitted first. That causes error on later reading again, since the items refer to data that are define in the columns, which are then still undefined, if that order is not maintained.

M.

Answer 1

For maintaining order on serialization the @Order annotation can be used (see this tutorial).

Also, in the specific context of serializing with simple-framework, Java List does not usually guarantee order, but you can use LinkedList for that matter.