java - How to persist a HashMap with hibernate

Question

Hello I am very new to the hibernate world and seem to have hit a roadblock. The object I need to store has a hashmap in it.

private Map<String, SentimentFrequencyCounts> modelData = null;

The thing is I will never need to search, sort or do any thing with this map I just need to save it with the object and load it when the object is loaded, so I was hoping there was some way that hibernate could just serializes it and then store it in a CLOB or BLOB field but I can not seem to find any way to do that.

So I next tried to have hibernate save this like so

    @OneToMany(mappedBy="ngram_data", fetch = FetchType.EAGER) 
 @MapKey(name = "attributeName") 
 public Map<String, SentimentFrequencyCounts> getModelData() {
  return modelData;
 }

But this gives me the following exception at runtime org.hibernate.AnnotationException: Use of @OneToMany or @ManyToMany targeting an unmapped class:

The SentimentFrequencyCounts class is an inner class of the one I am trying to persist. So basically I think I really am not understanding how hibernate works for hashmap. Really a shame I can not just get it to serialize this and lump it up in a single column.

Thanks in advance for your help and time.

Answer 1

@org.hibernate.annotations.Type(
        type = "org.hibernate.type.SerializableToBlobType", 
        parameters = { @Parameter( name = "classname", value = "java.util.HashMap" ) }
)
public Map<String, SentimentFrequencyCounts> getModelData() {
  return modelData;
}

Or even just this will work in most cases (distributed caching might be a problem):

@org.hibernate.annotations.Type( type = "org.hibernate.type.SerializableType" )
public Map<String, SentimentFrequencyCounts> getModelData() {
  return modelData;
}