Insert or update Solr document

See more:

SOLR

I have such schema of core:

<fields>
  <field name="Id" type="string" indexed="true" stored="true" required="true" />
  <field name="Date" type="date" indexed="false" stored="true" required="true"/>
  <field name="SearchWord" type="string" indexed="false" stored="true" required="true" />
  <field name="PartnerNr" type="int" indexed="true" stored="false" required="true" />
  <field name="CategoryNr" type="int" indexed="true" stored="false" required="true" />
  <field name="ArticlesCount" type="int" indexed="false" stored="true" required="true" />
</fields>

I need to insert document if there is no such in core or update Date and increment ArticlesCount if document exists.

How can I do it with SolrJ or send some http requests from DataImportHandler?