First of all, your script (ctx._source) doesn't do anything, as one of the commenters already pointed out. If you want to update, say, field "a", then you would need a script like:

ctx._source.a = "foobar"

This would assign the string "foobar" to field "a". You can do more than simple assignment, though. Check out the docs for more details and examples:

http://www.elasticsearch.org/guide/reference/api/update/

Updating multiple fields with one script is also possible. You can use semicolons to separate different MVEL instructions. E.g.:

ctx._source.a = "foo"; ctx._source.b = "bar"

In Elastic search have an Update Java API. Look at the following code

client.prepareUpdate("index","typw","1153")
            .addScriptParam("assignee", assign)
             .addScriptParam("newobject", responsearray)
            .setScript("ctx._source.assignee=assignee;ctx._source.responsearray=newobject ").execute().actionGet();

Here, assign variable contains object value and response array variable contains list of data.

You can do the same using spring java client using the following code. I am also listing the dependencies used in the code.

import org.elasticsearch.action.update.UpdateRequest;

import org.elasticsearch.index.query.QueryBuilder;

import org.springframework.data.elasticsearch.core.query.UpdateQuery;

import org.springframework.data.elasticsearch.core.query.UpdateQueryBuilder;

private UpdateQuery updateExistingDocument(String Id) {
    // Add updatedDateTime, CreatedDateTime, CreateBy, UpdatedBy field in existing documents in Elastic Search Engine
    UpdateRequest updateRequest = new UpdateRequest().doc("UpdatedDateTime", new Date(), "CreatedDateTime", new Date(), "CreatedBy", "admin", "UpdatedBy", "admin");

    // Create updateQuery
    UpdateQuery updateQuery = new UpdateQueryBuilder().withId(Id).withClass(ElasticSearchDocument.class).build();
    updateQuery.setUpdateRequest(updateRequest);

    // Execute update
     elasticsearchTemplate.update(updateQuery);
}

 XContentType contentType = 
 org.elasticsearch.client.Requests.INDEX_CONTENT_TYPE;
 public XContentBuilder getBuilder(User assign){
 try {
      XContentBuilder builder = XContentFactory.contentBuilder(contentType);
        builder.startObject();
      Map<String,?> assignMap=objectMap.convertValue(assign, Map.class);
                 builder.field("assignee",assignMap);
      return builder;
  } catch (IOException e) {
                log.error("custom field index",e);
}
      IndexRequest indexRequest = new IndexRequest();
        indexRequest.source(getBuilder(assign));
        UpdateQuery updateQuery = new UpdateQueryBuilder()
                                        .withType(<IndexType>)
                                        .withIndexName(<IndexName>)
                                        .withId(String.valueOf(id))
                                        .withClass(<IndexClass>)
                                        .withIndexRequest(indexRequest)
                                        .build();