JAXB annotation issue

Question

I need a little help with JAXB annotations. I have one XML that I want to get as a java object. If I will run it as it is I will get an error about the properties with the same name (see below). When I will comment out setters for lists in Feature and Scenario classes the error will disappear, but I will need those setters...

Error:

com.sun.xml.bind.v2.runtime.IllegalAnnotationsException: 2 counts of IllegalAnnotationExceptions
Class has two properties of the same name "scenarioList"
    this problem is related to the following location:
        at public java.util.ArrayList generator.model.Feature.getScenarioList()
        at generator.model.Feature
        at private java.util.ArrayList generator.model.Features.featureList
        at generator.model.Features
    this problem is related to the following location:
        at private java.util.ArrayList generator.model.Feature.scenarioList
        at generator.model.Feature
        at private java.util.ArrayList generator.model.Features.featureList
        at generator.model.Features
Class has two properties of the same name "stepList"
    this problem is related to the following location:
        at public java.util.ArrayList generator.model.Scenario.getStepList()
        at generator.model.Scenario
        at private java.util.ArrayList generator.model.Feature.scenarioList
        at generator.model.Feature
        at private java.util.ArrayList generator.model.Features.featureList
        at generator.model.Features
    this problem is related to the following location:
        at private java.util.ArrayList generator.model.Scenario.stepList
        at generator.model.Scenario
        at private java.util.ArrayList generator.model.Feature.scenarioList
        at generator.model.Feature
        at private java.util.ArrayList generator.model.Features.featureList
        at generator.model.Features

XML to parse:

<?xml version="1.0" encoding="UTF-8"?>
<features>
    <feature id="1">
        <name>Feature name 1</name>
        <description>Feature description 1</description>
        <scenarios>
            <scenario id="1">
                <name>Scenario name 1</name>
                <steps>
                    <step id="1"></step>
                    <step id="2"></step>
                </steps>
            </scenario>
            <scenario id="2">
                <name>Scenario name 2</name>
                <steps>
                    <step id="1"></step>
                    <step id="2"></step>
                </steps>
            </scenario>
        </scenarios>
    </feature>
    <feature id="2">
        <name>Feature name 2</name>
        <description>Feature description 2</description>
        <scenarios>
            <scenario id="4">
                <name>Scenario name 1</name>
                <steps>
                    <step id="1"></step>
                </steps>
            </scenario>
        </scenarios>
    </feature>
</features>

Here are the model classes:

Features.java

package generator.model;

import java.util.ArrayList;
import javax.xml.bind.annotation.XmlElement;
import javax.xml.bind.annotation.XmlRootElement;  

@XmlRootElement(name = "features")
public class Features {

    @XmlElement(name = "feature")
    private ArrayList<Feature> featureList = null;

    public void setFeaturesList(ArrayList<Feature> featureList) {
        this.featureList = featureList;
    }

    public ArrayList<Feature> getFeatureList() {
        return featureList;
    }
}

Feature.java

package generator.model;

import java.util.ArrayList;
import javax.xml.bind.annotation.XmlAttribute;  
import javax.xml.bind.annotation.XmlElement;
import javax.xml.bind.annotation.XmlElementWrapper;
import javax.xml.bind.annotation.XmlRootElement;  

@XmlRootElement(name = "feature")
public class Feature {  

    @XmlElementWrapper(name = "scenarios")
    @XmlElement(name= "scenario")
    private ArrayList<Scenario> scenarioList = null;

    private int id;
    private String name;
    private String description;

    @XmlAttribute
    public int getId() {  
        return id;  
    }  
    public void setId(int id) {  
        this.id = id;  
    } 

    @XmlElement
    public String getName() {  
        return name;  
    }

    public void setName(String name) {  
        this.name = name;  
    }  

    @XmlElement
    public String getDescription() {  
        return description;  
    }  

    public void setDescription(String description) {  
        this.description = description;  
    }


    public ArrayList<Scenario> getScenarioList() {
        return scenarioList;
    }

    public void setScenarioList(ArrayList<Scenario> scenarioList) {
        this.scenarioList = scenarioList;
    }

}  

Scenario.java

package generator.model;

import java.util.ArrayList;

import javax.xml.bind.annotation.XmlAttribute;  
import javax.xml.bind.annotation.XmlElement;
import javax.xml.bind.annotation.XmlElementWrapper;
import javax.xml.bind.annotation.XmlRootElement;  

@XmlRootElement(name = "scenario")
public class Scenario {  

    @XmlElementWrapper(name = "steps")
    @XmlElement(name= "step")
    private ArrayList<Step> stepList = null;

    private int id;
    private String name;

    @XmlAttribute
    public int getId() {  
        return id;  
    }  
    public void setId(int id) {  
        this.id = id;  
    } 

    @XmlElement
    public String getName() {  
        return name;  
    }  
    public void setName(String name) {  
        this.name = name;  
    }

    public ArrayList<Step> getStepList() {
        return stepList;
    }

    public void setStepList(ArrayList<Step> stepList) {
        this.stepList = stepList;
    }  

}  

Step.java

package generator.model;

import javax.xml.bind.annotation.XmlAttribute;  
import javax.xml.bind.annotation.XmlRootElement;  

@XmlRootElement(name = "step")
public class Step {  

    private int id;

    @XmlAttribute
    public int getId() {  
        return id;  
    }  
    public void setId(int id) {  
        this.id = id;  
    } 

}  

Answer 1

JAXB automatically maps fields or properties. If the @XmlAccessorType is absent, then the default is XmlAccessType.PUBLIC_MEMBER, that means (see javadoc)

Every public getter/setter pair and every public field will be automatically bound to XML, unless annotated by XmlTransient.

In your case, by default, all public getter/setter are mapped even if no annotation is present. Fields are not mapped, because they are private, unless explicitly annotated.

So, there is a conflict with stepList and scenarioList that are mapped two times: The public getter/setter, because @XmlAccessorType is absent, and the field, because it is annotated.

And note that in your Features class, you will have a <feature> element (annotated private featureList field), and a <featureList> element (public getter for featureList), both with the same content.

You could avoid it, adding an @XmlTransient annotation to the property getter to avoid the automatic mapping. But I would suggest choosing to map either fields or properties, and specify the @XmlAccessorType accordingly.

For example, your Scenario.java could be mapped with:

// Non static, non transient fields will be automatically be mapped unless annotated with XmlTransient.
@XmlAccessorType(XmlAccessType.FIELD)
@XmlRootElement(name = "scenario")
public class Scenario {  

    @XmlElementWrapper(name = "steps")
    @XmlElement(name= "step")
    private ArrayList<Step> stepList = null;

    @XmlAttribute
    private int id;

    // Mapping a field to an element is the default, so this annotation is not strictly
    // needed, unless you want to change the default element name
    @XmlElement
    private String name;

    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 ArrayList<Step> getStepList() {
        return stepList;
    }

    public void setStepList(ArrayList<Step> stepList) {
        this.stepList = stepList;
    }  

}