elasticsearch 5.2.2 java addsort has error

Question

When I use elasticsearch java api to sort my document, the es has error:

Caused by: java.lang.IllegalArgumentException: Fielddata is disabled on text fields by default. Set fielddata=true on [namespaceName] in order to load fielddata in memory by uninverting the inverted index. Note that this can however use significant memory.

And my code for sorting like this:

SortBuilder sortBuilder = SortBuilders.fieldSort(sortField)
                .order(SortOrder.valueOf(order.toUpperCase()));
SearchRequestBuilder srb1 = client.prepareSearch()
                .setQuery(qb).setIndices(indexName)
                .setTypes(type).addSort(sortBuilder);

I want to know how to set fielddata=true by java api.