<Jörg>
Well, no. Not really. See, XStream is about Java object to XML *and back*,
i.e. every example can also unmarshal.
Therefore adjust the marshalling. If XStream generates the required XML
format, it can also read it. It is a very tedious and annoying task to try
it the other way round (you already found this out), because you never know
- especially as starter - why XStream throws an exception or silently skips
some elements.
</Jörg>
<me>
Typically, the use cases will be objects->xml for use by 3rd party or
xml->objects where inbound xml was created by a 3rd party. Unless i was
simply persisting and reading unmodified serialized data, i would expect
that the inbound and outbound xml is different and created/digested by
applications that may not even be java.
i created (marshalled/serialized) some test xml as follows:
Persons ps = new Persons();
Person p1 = new Person();
p1.setName("joe");
s.getPersons().add(p1);
Person p2 = new Person();
p1.setName("blo");
ps.getPersons().add(p2);
System.out.println(xstream.toXML(ps));
while i *try* to unmarshalled/deserialize as follows:
XStream xstream = new XStream(new StaxDriver());
stream.alias("persons", Persons.class);
xstream.alias("person", Person.class);
xstream.addImplicitCollection(Person.class, "person");
etc.
These seems to be a very different set of methods. My problem is that i
can't find adequate examples (or documentation) on how to use alias() and
addImplicitCollection() methods when unmarshalling collections.
</me>
---
<Jörg>
Why do you think the objects have to be POJOs?
</Jörg>
<me>
My xml needs to get deserialized into objects and then those objects used
by the application. Why not unmarshall directly into my existing POJOs
instead of having to create a whole new set of "command" (abstraction)
classes whose only difference is that their accessors/mutators are get(),
add() instead of the POJO standard get(), set()?
Things are much cleaner if i can (un)marshall using a simple library and
leave my domain unmodified (which is why i'm trying to avoid xstream
annotations).
I questioned the requirement of get(), add() and collections as lists,
because that is whats used in the examples and i thought maybe they were
required.
</me>
On Tue, May 20, 2014 at 6:22 AM, Jörg Schaible <joerg.schai...@swisspost.com
> wrote:
> Hi John,
>
> js wrote:
>
> > hi,
> >
> > I'll eventually figure this out, but i have been struggling for at least
> 2
> > days trying to unmarshall the simplest xml.. i must really be getting
> > frustrated if i resorted to emailing the open source developers.. anyway:
> >
> > all i want to do is unmarshall a simple xml file involving nested
> > collections
> >
> > <persons>
> > <person><name>billy</name>
> > <address>
> > <address1>West St.</address1>
> > </address>
> > <address>
> > <address1>East St.<address1>
> > </address>
> > </person>
> > <person><name>bob</name>
> > <address>
> > <address1>North St.</address1>
> > </address>
> > <address>
> > <address1>South St.<address1>
> > </address>
> > </person>
> > </persons>
> >
> >
> > i have tried all the examples at codehaus (which are all
> > marshall-centric).
>
>
> Well, no. Not really. See, XStream is about Java object to XML *and back*,
> i.e. every example can also unmarshal.
>
>
> > i have googled countless sites.
> > no where have i found a simple, complete example that does this most
> basic
> > of requirements.
>
>
> Because it's not necessary? ... see below ;-)
>
>
> > if collections are created, they are either null or empty.
> > Lots of: No field "person" for implicit collection errors as well.
> >
> > ====== CODE =========
> >
> > public class Persons {
> >
> > private List<Person> persons = new ArrayList<Person>();
> >
> > public List<Person> getPersons() {
> > return persons;
> > }
> > public void setPersons(List<Person> persons) {
> > this.persons = persons;
> > }
> >
> > }
> > //this is a "command" class as one does not need a model class for
> > "persons" thus the List instead of Set (i was just following examples i
> > found online, but would rather it be a set as well).
>
>
> You may also use directly an array (Person[]).
>
>
> > //also, why examples have get() and add(), instead of POJO get(), set()?
>
>
> Why do you think the objects have to be POJOs?
>
>
> > ---------
> >
> > public class Person {
> >
> > private String name;
> > private Set<Address> addresses = new HashSet<Address>();
> >
> > public String getName() {
> > return name;
> > }
> > public void setName(String name) {
> > this.name = name;
> > }
> >
> >
> > public Set<Address> getAddresses() {
> > return addresses;
> > }
> > public void setAddresses(Set<Address> addresses) {
> > this.addresses = addresses;
> > }
> > }
> >
> > //are complete constructors required?
>
>
> Neither constructors nor setters are required.
>
> > -------------
> >
> > public class Address {
> >
> > private String address1;
> >
> > public String getAddress1() {
> > return address1;
> > }
> > public void setAddress1(String address1) {
> > this.address1 = address1;
> > }
> >
> > }
> >
> > --------------
> >
> > public void personsFromXML(MultipartFile xml) {
> > XStream xstream = new XStream(new StaxDriver());
> > Persons persons = new Persons();
> > xstream.alias("persons", Persons.class);
> >
> > try {
> > persons = (Persons)xstream.fromXML(xml.getInputStream());
> >
> > }
> > catch(Exception e){
> > e.printStackTrace();
> > }
> >
> > --------------
> >
> > i have tried annotations in Persons.class as well as all variations of
> the
> > below (+ others):
> > //xstream.addImplicitCollection(Person.class, "person");
> > //xstream.alias("persons", Persons.class);
> > //xstream.alias("person", Person.class);
> > //xstream.alias("address", Address.class);
> > //xstream.addImplicitCollection(Person.class, "person");
> > //xstream.addImplicitCollection(Person.class, "person",
> > Persons.class);
> > //xstream.addImplicitCollection(Persons.class, "person",
> > Person.class);
>
>
> http://xstream.codehaus.org/faq.html#XML_unmarshalling_fails
>
> Therefore adjust the marshalling. If XStream generates the required XML
> format, it can also read it. It is a very tedious and annoying task to try
> it the other way round (you already found this out), because you never know
> - especially as starter - why XStream throws an exception or silently skips
> some elements.
>
>
> > how does xstream know that collection A is within Persons.class, but
> > collection B is in Person.class?
>
>
> Java reflection.
>
>
> > are the generic converters being used when xtream performs its
> > auto-deserialization magic?
>
>
> Since XStream has obviously no built-in converters for Person or Address,
> it
> has to use the generic converters (based on reflection).
>
>
> > are aliases and implicitCollections handled diff when marshall v.
> > unmarshall?
>
>
> No. That's the point. Adjust the XStream and write an object as XML and you
> will see immediately what has been influenced.
>
> Hope this helps,
> Jörg
>
>
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