Question

I’m using JAXB to generate a XML Schema from my Java classes so the other developers can create instances of the classes easily without knowledge in Java.

Here’s the relevant part of the code:

package-info.java

@XmlSchema(xmlns = @XmlNs(prefix = "p", namespaceURI = "http://mygame.com"),
           namespace = "http://mygame.com")

package com.mygame.entity.properties;

import javax.xml.bind.annotation.XmlNs;
import javax.xml.bind.annotation.XmlSchema;

Model.class

package com.mygame.entity.properties;

@XmlType(name = "model", namespace = "http://mygame.com")
@XmlRootElement(name = "model", namespace = "http://mygame.com")
public class Model {

    @XmlAttribute(required = true)
    public String path;

    public Model() {
    }
}

Unit.class

@XmlType(name="unit", namespace="http://mygame.com")
@XmlRootElement(name="unit", namespace="http://mygame.com")
public class Unit extends GameObject {
}

GameObject.class

@XmlType(name = "gameobject", namespace = "http://mygame.com")
public abstract class GameObject extends Thing {

    // Attributes
    public Armor armor;
    public Short maxHp;
    public Boolean walkable = false;
    public AbstractModel model;
}

Thing.class

@XmlType(name="thing", namespace="http://mygame.com")
public abstract class Thing {
    // Constants
    // Attributes

    @XmlElement(required=false)
    public String icon;
}

Generated XML Schema

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<xs:schema version="1.0" targetNamespace="http://mygame.com" xmlns:e="http://mygame.com" xmlns:s="http://mygame.com" xmlns:tns="http://mygame.com" xmlns:p="http://mygame.com" xmlns:xs="http://www.w3.org/2001/XMLSchema">


  <xs:element name="model" type="tns:model"/>

  <xs:element name="unit" type="tns:unit"/>

  <xs:complexType name="thing" abstract="true">
    <xs:sequence>
      <xs:element name="icon" type="xs:string" minOccurs="0"/>
    </xs:sequence>
  </xs:complexType>

  <xs:complexType name="unit">
    <xs:complexContent>
      <xs:extension base="tns:gameobject">
        <xs:sequence/>
      </xs:extension>
    </xs:complexContent>
  </xs:complexType>

  <xs:complexType name="gameobject" abstract="true">
    <xs:complexContent>
      <xs:extension base="tns:thing">
        <xs:sequence>
          <xs:element ref="tns:armor" minOccurs="0"/>
          <xs:element name="maxHp" type="xs:short" minOccurs="0"/>
          <xs:element name="walkable" type="xs:boolean" minOccurs="0"/>
          <xs:element ref="tns:model" minOccurs="0"/>
        </xs:sequence>
      </xs:extension>
    </xs:complexContent>
  </xs:complexType>

  <xs:complexType name="model">
    <xs:sequence/>
    <xs:attribute name="path" type="xs:string" use="required"/>
  </xs:complexType>


</xs:schema>

Up to this point, everything is fine. It generates correctly a wanted XML (althought with those annoying TNS prefix, but that’s fine).

The problem is when I try to unmarshall a UNIT, I’m getting an error in one of the cases

Case 1 – Working

Given this XML input, everything works fine and I get a instance of my class correctly.

<?xml version="1.0" encoding="UTF-8"?><tns:unit xmlns:tns="http://mygame.com" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="/home/shirkit/jMonkeyProjects/Fortress Wars/Core/schema/full.xsd">
<maxHp>100</maxHp>
<walkable>false</walkable>
<model path="Models/Oto/Oto.mesh.xml"/></tns:unit>

Case 2 – Not working

Given this, I get an error described below

<?xml version="1.0" encoding="UTF-8"?><tns:unit xmlns:tns="http://mygame.com" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="/home/shirkit/jMonkeyProjects/Fortress Wars/Core/schema/full.xsd">
<maxHp>100</maxHp>
<walkable>false</walkable>
<tns:model path="Models/Oto/Oto.mesh.xml"/></tns:unit>


unexpected element (uri:"http://mygame.com", local:"model"). Expected elements are <{}icon>,<{}model>,<{}walkable>,<{}armor>,<{}maxHp>

The only difference between the two XML input is that one has the element model, and the other has the element tns:model. I don’t know why I’m getting this error in the Case 2, can someone give me an explanation for that?

Answer 1

you either need to drop the tns prefix from the model element or specify in your schema the “elementFormDefault” value of QUALIFIED (personally, i prefer this solution).