@Field
    public void setSolrCollection(String solrCollection) {
        this.solrCollection = solrCollection;
    }
Specify the field in the first Metadata that should be
used as the id field for the document.

@param idField
tika-pipes/tika-emitters/tika-emitter-solr/src/main/java/org/apache/tika/pipes/emitter/solr/SolrEmitter.java