How to marshal/unmarshal abstract class with a different tags using JAXB - jaxb

Question

<root-object>
<synchronous>
<command>C:\hello_world.exe</command>
<argument>aaaa</argument>
<argument>bbbb</argument>
</synchronous>
<asynchronous>
<command>C:\hello_world.exe</command>
<argument>aaaa</argument>
<argument>bbbb</argument>
</asynchronous>
<synchronous>
<command>C:\hello_world.exe</command>
<argument>aaaa</argument>
<argument>bbbb</argument>
</synchronous>
</root-object>
In this XML format, I want to unmarshal/marshal synchronous and asynchronous objects into a single list through JAXB.
I wrote the code as below, but nothing was entered in the items.
How can I make be this structure possible?
#XmlRootElement(name = "root-object")
#XmlAccessorType(XmlAccessType.FIELD)
#lombok.ToString
public class RootObject {
#XmlElement(type = CommandItem.class)
private List<CommandItem> items= new ArrayList<>();
public RootObject() {}
#lombok.Getter
#lombok.Setter
#lombok.NoArgsConstructor
#XmlType
#XmlSeeAlso({AsyncCommandItem.class, SyncCommandItem.class})
#XmlAccessorType(XmlAccessType.FIELD)
public static class CommandItem {
#XmlElement(name = "command")
private String command;
#XmlElement(name = "argument")
private List<String> argument;
}
#lombok.NoArgsConstructor
#XmlRootElement(name = "synchronous")
public static class SyncCommandItem extends CommandItem {
}
#lombok.NoArgsConstructor
#XmlRootElement(name = "asynchronous")
public static class AsyncCommandItem extends CommandItem {
}
}

Answer 1

I used the following code for the XML you have provided and it seems to work fine for me. You need to modify the POJO a bit in order to make it work.
RootObject.class:
#XmlRootElement(name = "root-object")
#Data
#XmlAccessorType(XmlAccessType.FIELD)
public class RootObject {
#XmlElement(name = "synchronous")
private List<Synchronous> synchronous;
#XmlElement(name = "asynchronous")
private List<Asynchronous> asynchronous;
}
Synchronous.class:
#Data
#XmlAccessorType(XmlAccessType.NONE)
public class Synchronous {
#XmlElement(name = "command")
private String command;
#XmlElement(name = "argument")
private List<String> argument;
}
Asynchronous.class:
#Data
#XmlAccessorType(XmlAccessType.NONE)
public class Asynchronous {
#XmlElement(name = "command")
private String command;
#XmlElement(name = "argument")
private List<String> argument;
}
Main.class:
public class Main {
public static void main(String[] args) throws JAXBException, XMLStreamException {
final InputStream inputStream = Unmarshalling.class.getClassLoader().getResourceAsStream("synchronous.xml");
final XMLStreamReader xmlStreamReader = XMLInputFactory.newInstance().createXMLStreamReader(inputStream);
final Unmarshaller unmarshaller = JAXBContext.newInstance(RootObject.class).createUnmarshaller();
final RootObject rootObject = unmarshaller.unmarshal(xmlStreamReader, RootObject.class).getValue();
System.out.println(rootObject.toString());
Marshaller marshaller = JAXBContext.newInstance(RootObject.class).createMarshaller();
marshaller.setProperty(Marshaller.JAXB_FRAGMENT, Boolean.TRUE);
marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, Boolean.TRUE);
marshaller.marshal(rootObject, System.out);
}
}
Following is the output:
RootObject(synchronous=[Synchronous(command=C:\hello_world.exe, argument=[aaaa, bbbb]), Synchronous(command=C:\hello_world.exe, argument=[aaaa, bbbb])], asynchronous=[Asynchronous(command=C:\hello_world.exe, argument=[aaaa, bbbb])])
<root-object>
<synchronous>
<command>C:\hello_world.exe</command>
<argument>aaaa</argument>
<argument>bbbb</argument>
</synchronous>
<synchronous>
<command>C:\hello_world.exe</command>
<argument>aaaa</argument>
<argument>bbbb</argument>
</synchronous>
<asynchronous>
<command>C:\hello_world.exe</command>
<argument>aaaa</argument>
<argument>bbbb</argument>
</asynchronous>
</root-object>

Answer 2

I solved it by #XmlElements.
#XmlRootElement(name = "root-object")
#XmlAccessorType(XmlAccessType.FIELD)
#lombok.ToString
public class RootObject {
#XmlElements({
#XmlElement(name = "synchronous", type = SyncCommandItem.class),
#XmlElement(name = "asynchronous", type = AsyncCommandItem .class),
})
private List<CommandItem> items= new ArrayList<>();
public RootObject() {}
#lombok.Getter
#lombok.Setter
#lombok.NoArgsConstructor
#XmlType
#XmlSeeAlso({AsyncCommandItem.class, SyncCommandItem.class})
#XmlAccessorType(XmlAccessType.FIELD)
public static class CommandItem {
#XmlElement(name = "command")
private String command;
#XmlElement(name = "argument")
private List<String> argument;
}
#lombok.NoArgsConstructor
#XmlRootElement(name = "synchronous")
public static class SyncCommandItem extends CommandItem {
}
#lombok.NoArgsConstructor
#XmlRootElement(name = "asynchronous")
public static class AsyncCommandItem extends CommandItem {
}
}