private void addMetadataToSolrInputDocument(Metadata metadata,
                                                SolrInputDocument solrInputDocument,
                                                UpdateStrategy updateStrategy) {
        for (String n : metadata.names()) {
            String[] vals = metadata.getValues(n);
            if (vals.length == 0) {
                continue;
            } else if (vals.length == 1) {
                if (updateStrategy == UpdateStrategy.ADD) {
                    solrInputDocument.setField(n, vals[0]);
                } else {
                    solrInputDocument.setField(n, new HashMap<String, String>() {
                        {
                            put("set", vals[0]);
                        }
                    });
                }
            } else if (vals.length > 1) {
                if (updateStrategy == UpdateStrategy.ADD) {
                    solrInputDocument.setField(n, vals);
                } else {
                    solrInputDocument.setField(n, new HashMap<String, String[]>() {
                        {
                            put("set", vals);
                        }
                    });
                }
            }
        }
    }
You can specify solrUrls, or you can specify solrZkHosts and use use zookeeper to determine the solr server urls.
tika-pipes/tika-emitters/tika-emitter-solr/src/main/java/org/apache/tika/pipes/emitter/solr/SolrEmitter.java