In order for the code bellow to work:

► Make sure to enable Streaming in "solrconfig.xml":

<requestParsers enableStreamBody="true" />

Visit this page for more details: http://lucene.apache.org/solr/guide/8_5/requestdispatcher-in-solrconfig.html

► Make sure to update the variables ("solrUrl", "collectionName", ...) with your information.

► Make sure to add the fields "id" and "field1" to your SchemaXml.

To force the commit, make sure to set the property "openSearcher" to true (SolrConfigXml file -> updateHandler -> autoCommit)

Note: You can also force the commit by running the URL: http://localhost:8983/solr/COLLECTION-NAME/update?commit=true

Update documents (stream.body) using the request handler /update:

final String UPDATE_REQUEST_PATH = "/update";

final String[] solrUrl = { "http://localhost:8983/solr" };

final String collectionName = "collection1";

// org.apache.solr.common.params.CommonParams.STREAM_BODY = "stream.body";

// org.apache.solr.common.params.CollectionAdminParams.COLLECTION = "collection";

final CloudSolrClient cloudSolrClient = new CloudSolrClient.Builder(Arrays.asList(solrUrl)).build();

cloudSolrClient.setDefaultCollection(collectionName);

// updating documents [/update] [ModifiableSolrParams] [stream.body]
{
    final String streamBody = "<add><doc><field name=\"id\">1</field><field name=\"dynamicField1_s\" update=\"set\">dynamicField1_s 1-1</field><field name=\"field1\" update=\"set\">field1 1-1</field></doc></add>";

    final ModifiableSolrParams modifiableSolrParams = new ModifiableSolrParams();

    modifiableSolrParams.add(CommonParams.STREAM_BODY, streamBody);
    modifiableSolrParams.add(CollectionAdminParams.COLLECTION, collectionName);

    final UpdateRequest updateRequest = new UpdateRequest();

    updateRequest.setParams(modifiableSolrParams);
    updateRequest.setPath(UPDATE_REQUEST_PATH);
    updateRequest.setMethod(METHOD.POST);

    final NamedList<Object> response = cloudSolrClient.request(updateRequest);

    System.out.println(response);
}

cloudSolrClient.close();