Question

I’m trying to get a XmlAdapter to a HashMap to work and I keep getting an exception. I followed this blog entry very closely, and I’ve been over my code many times yet I don’t see the issue.

I am using the latest version of org.eclipse.persistence.jaxb.JAXBContextFactory as my JAXB provider.

Here is a sample of my XML:

<test>
  <myName>Paul</myName>
  <mappings>
    <entry key="man">manufacturer</entry>
    <entry key="prod">product</entry>
  </mappings>
<test>

Following the steps in the blog post mentioned above:

1. Identify the Unmappable Class

I’m trying to map a java.util.HashMap.

2. Create an Equivalent Class that is Mappable

public class MappingType
{
  public List<MappingEntryType> entry = new ArrayList<MappingEntryType>();
}

public class MappingEntryType
{
  @XmlAttribute
  public String key;
  @XmlValue
  public String value;
}

3. Create an XmlAdapter to Convert Between Unmappable and Mappable Objects

public class MappingAdapter extends XmlAdapter<MappingType,
                                               HashMap<String, String>>
{
  @Override
  public HashMap<String, String> unmarshal(MappingType v> throws Exception
  {
    HashMap<String, String> hashMap = new HashMap<String, String>();
    for (MappingTypeEntry mappingEntry : v.entry)
    {
      hashMap.put(mappingEntry.key, mappingEntry.value);
    }
    return hashMap;
  }

  // marshal is here but I'm just working on unmarshalling now
}

4. Specify the XmlAdapter

@XmlAccessorType(XmlAccessType.FIELD)
@XmlRootElement(name = "test")
public class TestEntity
{
  @XmlElement
  private String myName;

  @XmlJavaTypeAdapter(MappingAdapter.class)
  HashMap<String, String> mappings;

  // getters & setters omitted in a feeble attempt at brevity
}

I have added the next step, which I call
5. Stack Trace

Exception [EclipseLink-3001](Eclipse Persistence Services-2.3.0.v20110604-r9504):
org.eclipse.persistence.exceptions.ConversionException
ExceptionDescription: The object [mypackage.MappingType@145d424], of class
[class mypackage.MappingType],could not be converted to [class java.util.HashMap]
  at etc etc

The exception description is very clear but I can’t see where I am trying to convert a MappingType to a HashMap. Sometimes typing a question leads me to the answer but not this time.

I’m sure it’s something simple – if you see my mistake please point it out!

Thanks!

By the way, Blaise Doughan’s blog is full of great JAXB and MOXy information, worth checking out.

Answer 1

I figured how to fix the issue, even if I don’t understand what was happening.

I am using the Spring framework with this project and my XmlAdapter class was marked as @Component. Removing that annotation made the code work perfectly. For some reason having my adapter managed by Spring prevented my JAXB provider from using the class to unmarshal my XML.