title: Use of _id for document identifier in elastic search
body: <p>I have a document with _id as a parameter. I have the below JSON</p>
  
  <pre><code>{  
     "_id":{  
        "$oid":"52af48b5d55148fa0c199643"
     },
     "email":"example.ex@example.com"
  }
  </code></pre>
  
  <p>Corresponding Java class:</p>
  
  <pre><code>@Document(indexName = "Test")
  public class Test {
  
    @Id
    @ObjectId
    private String _id;
  
    private String email;
  }
  </code></pre>
  
  <p>The conversion of json object is successful but there is a problem in saving the data to elastic search.</p>
  
  <pre><code>org.elasticsearch.index.mapper.MapperParsingException: Field [_id] is a metadata field and cannot be added inside a document. Use the index API request parameters
  </code></pre>
  
  <p>I have seen some references and came to a conclusion that i cannot use _id.. But am looking for a way to use a JsonProperty but it also does not work as i guess ObjectId uses JsonProperty internally.</p>
  
  <p>Kindly provide suggestions</p>