Retrieving the UUID from Apache Solr after a commit

I am using Solrj to add new documents to a Solr instance. In my document schema the id is a UUID (solr.UUIDField). Each time a document is created the id is filled with the unique id, which is exactly what I want. Sometimes it's necessary in my application that I can retrieve this unique id to add it as a field value when inserting another document. So my question is, how can I retrieve this generated uuid from solr after adding a document?

Solrj returns me this UpdateResponse object after commiting, but I don't know how to get the new uuid out of it.

I am addin开发者_运维知识库g a document like this

CommonsHttpSolrServer server = new CommonsHttpSolrServer(MY_SERVER_URL);

SolrInputDocument doc = new SolrInputDocument();
// [...] multiple addField calls
server.add(doc);
UpdateResponse ur = server.commit();

AFAIK you aren't going to ever get a UUID from an add or a commit. When you do an add or commit, the update request handler gives you back query time and status, but not much else (assuming it is successful). You can actually see what is in the HTTP response by running a manual add/commit like so:

http://localhost:8983/solr/update?stream.body=<add><doc><field name="id">test</field><field name="title">test title</field></doc></add>
http://localhost:8983/solr/update?stream.body=<commit/>

If you run those queries in a web browser, they will submit a test document and commit it, respectively. You will then be able to see what information is available to SolrJ (not much).

You could write your own (modified) update handler in Java, but that seems like a ton of work. You could also enable the "timestamp" field in your Solr schema so you can query solr by last modified date and find the items you just committed.

Both of those methods would be major hacks, though. Your best bet is to figure out a unique ID for your documents before you submit them to Solr, then use that unique ID to retrieve them. Using a generated UUID is more of a "fire and forget about this" method. Since you don't want to forget, you will need to generate your own UUID.

Since you're using Java, it should be dead simple to do with UUID, using some code like this:

CommonsHttpSolrServer server = new CommonsHttpSolrServer(MY_SERVER_URL);

SolrInputDocument doc = new SolrInputDocument();
UUID uuid = UUID.randomUUID();
doc.addField("id", uuid.toString());
// [...] multiple addField calls
server.add(doc);
UpdateResponse ur = server.commit();