Implementing Inheritance in Spring Solr Data

In our solr data model, there is inheritance relationship between classes.

Please check about why we are mixing Spring Data Solr and SolrJ to make it work with Solr Cloud 5.

In the DAO:

public BaseModel findOne(final String id) {
    final SolrDocument doc = solrServer.getById(getCollection(), id);;
    if (doc == null) {
        throw new WrappedException(ErrorCode.INVALID_PARAMETER, "BaseModel not found: " + id);
    }
    return converter.read(BaseModel.class, doc);
}

But this will cause Spring Data Solr returns BaseModel object not its concrete sub-classes which we expected.

To fix this, we need change SolrConverter's read method to map to its concrete sub-classes in Spring configuration class.

@Bean
public static SolrConverter mappingSolrConverter() {
    final MappingContext<? extends SolrPersistentEntity<?>, SolrPersistentProperty> mappingContext =
            new SimpleSolrMappingContext();
    final MappingSolrConverter converter = new MappingSolrConverter(mappingContext) {
        @SuppressWarnings("unchecked")
        @Override
        protected <S> S read(final TypeInformation<S> targetTypeInformation, final Map<String, ?> source) {
            final Object obj = source.get(BaseModel.FIELD_TYPE);
            if (obj != null) {
                final String type = String.valueOf(obj);
                switch (type) {
                    case BaseModel.TYPE_A:
                        return (S) super.read(ClassTypeInformation.from(ModelA.class), source);
                    case BaseModel.TYPE_B:
                        return (S) super.read(ClassTypeInformation.from(ModelB.class), source);
                    case BaseModel.TYPE_C:
                        return (S) super.read(ClassTypeInformation.from(ModelC.class), source);
                    default:
                        throw new IllegalArgumentException(
                                "invalid " + BaseModel.FIELD_TYPE + ", value: " + type);
                }
            }
            return super.read(targetTypeInformation, source);
        }
    };
    return converter;
}