Question

JAXB Object that contains ether a map or simple types

The Idea is to have a class that has a member “value” which can contain simple types like String or Integer and also a Map of simple types, connected to a boolean value (eg. HashMap

Here is a “working” example, which shows what I want to do:

package test;

import java.io.File;
import java.util.HashMap;
import java.util.Map;

import javax.xml.bind.JAXB;
import javax.xml.bind.annotation.XmlElement;
import javax.xml.bind.annotation.XmlElements;
import javax.xml.bind.annotation.XmlRootElement;
import javax.xml.bind.annotation.XmlSeeAlso;

@XmlRootElement
public class TestJAXB {
    public static void main(String[] args) {
        TestJAXB test = new TestJAXB();
        JAXB.marshal(test, new File("foo.xml"));
    }

    Container one;
    Container two;
    Container three;
    Container four;

    public TestJAXB() {
        this.one = new Container("foo");
        this.two = new Container("42");
        this.three = new Container(true);

        HashMap<Object, Boolean> map = new HashMap<Object, Boolean>();
        map.put("foo", false);
        map.put("bar", false);
        map.put("foobar", true);

        this.four = new Container(map);

    }

    @XmlElement
    public Container getOne() {
        return one;
    }

    public void setOne(Container one) {
        this.one = one;
    }

    @XmlElement
    public Container getTwo() {
        return two;
    }

    public void setTwo(Container two) {
        this.two = two;
    }

    @XmlElement
    public Container getThree() {
        return three;
    }

    public void setThree(Container three) {
        this.three = three;
    }

    @XmlElement
    public Container getFour() {
        return four;
    }

    public void setFour(Container four) {
        this.four = four;
    }
}

@XmlRootElement
@XmlSeeAlso(HashMap.class)
class Container {
    Map<Object, Boolean> value = null;
    boolean wasMap = false;

    protected Container() {

    }

    protected Container(Object value) {
        this.setValue(value);
    }

    @XmlElements({ @XmlElement(name = "string", type = String.class), @XmlElement(name = "bool", type = Boolean.class), @XmlElement(name = "int", type = Integer.class), })
    public Object getValue() {
        if (wasMap) {
            return value;
        } else {
            return value.keySet().toArray()[0];
        }
    }

    @SuppressWarnings("unchecked")
    public void setValue(Object value) {
        if (value instanceof Map) {
            this.value = (Map<Object, Boolean>) value;
            this.wasMap = true;
        } else {
            this.value = new HashMap<Object, Boolean>();
            this.value.put(value, false);
            this.wasMap = false;
        }
    }
}

Well, the simple types are marshalled to fine xml, but the element for the map stays empty:

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<testJAXB>
    <four>
        <string xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:type="hashMap"/>
    </four>
    <one>
        <string>foo</string>
    </one>
    <three>
        <bool>true</bool>
    </three>
    <two>
        <string>42</string>
    </two>
</testJAXB>

What did I do wrong? What can I do?

Answer 1

You must create javax.xml.bind.annotation.adapters.XmlAdapter for HashMap.
Example you can get here
Example