How to unmarshal xml message with bad parent/child model - jaxb

Question

I am trying to unmarshal a 3rd party XML payload into a class. The problem is that the payload has a parent/child relationship and the root node, the parent and the children all have the same element name. Here is a sample of the payload.
<?xml version="1.0" encoding="UTF-8"?>
<Directory>
<id>2</id>
<name>Media</name>
<Directory>
<id>5</id>
<name>Default_Content</name>
<Directory>
<id>9</id>
<name>Images</name>
</Directory>
<Directory>
<id>8</id>
<name>Icons</name>
</Directory>
<Directory>
<id>6</id>
<name>Additional_Content</name>
</Directory>
</Directory>
<Directory>
<id>12</id>
<name>IC</name>
</Directory>
</Directory>
So I am trying to annotate a class so JAXB/JAX-RS can unmarshal this into something useful.
I've tried something like this
#XmlRootElement(name="Directory")
public class Directory {
private int id;
private String name;
#XmlElement(name="Directory");
private List<Directory> directories = new ArrayList<Directory>();
}
But, predictably, it throws an IllegalAnnotationException because of having 2 properties with the same name.
Any ideas as to how I can use JAXB/JAX-RS to cleanly handle this mess or should I just parse it on my own?

Answer 1

Short Answer
The exception is due to a field/property collision. You can either annotate the properties (get methods) or set the following annotation on your type:
#XmlAccessorType(XmlAccessType.FIELD)
public class Directory {
...
}
Long Answer
JAXB's default access type is PUBLIC_MEMBER this means that JAXB will map all public fields (instance variables) and properties (get/set methods).
public class Foo {
private String bar;
public String getBar() {
return bar;
}
public void setBar(String bar) {
this.bar = bar;
}
}
If you annotate a field:
public class Foo {
#XmlAttribute
private String bar;
public String getBar() {
return bar;
}
public void setBar(String bar) {
this.bar = bar;
}
}
Then JAXB will think it has two bar properties mapped and thrown an exception:
Exception in thread "main" com.sun.xml.bind.v2.runtime.IllegalAnnotationsException: 1 counts of IllegalAnnotationExceptions
Class has two properties of the same name "bar"
this problem is related to the following location:
at public java.lang.String example.Foo.getBar()
at example.Foo
this problem is related to the following location:
at private java.lang.String example.Foo.bar
at example.Foo
The solution is to annotate the property and set the XmlAccessType type to FIELD
#XmlAccessorType(XmlAccessType.FIELD)
public class Foo {
#XmlAttribute
private String bar;
public String getBar() {
return bar;
}
public void setBar(String bar) {
this.bar = bar;
}
}
Your Model
Directory
import java.util.ArrayList;
import java.util.List;
import javax.xml.bind.annotation.XmlAccessorType;
import javax.xml.bind.annotation.XmlAccessType;
import javax.xml.bind.annotation.XmlElement;
import javax.xml.bind.annotation.XmlRootElement;
#XmlRootElement(name="Directory")
#XmlAccessorType(XmlAccessType.FIELD)
public class Directory {
private int id;
private String name;
#XmlElement(name="Directory")
private List<Directory> directories = new ArrayList<Directory>();
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public List<Directory> getDirectories() {
return directories;
}
public void setDirectories(List<Directory> directories) {
this.directories = directories;
}
}
Demo
import java.io.File;
import javax.xml.bind.JAXBContext;
import javax.xml.bind.Marshaller;
import javax.xml.bind.Unmarshaller;
public class Demo {
public static void main(String[] args) throws Exception {
JAXBContext jc = JAXBContext.newInstance(Directory.class);
Unmarshaller unmarshaller = jc.createUnmarshaller();
Directory directory = (Directory) unmarshaller.unmarshal(new File("input.xml"));
Marshaller marshaller = jc.createMarshaller();
marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true);
marshaller.marshal(directory, System.out);
}
}