Is it possible to rename _id field after mongo's group aggregation? : <p>I have a query like this (simplified):</p>

<pre><code>db.report.aggregate([{
        $match: {
            main_id: ObjectId("58f0f67f50c6af16709fd2c7")
        }
    }, {
        $group: {
            _id: "$name",
            count: {
                $sum: 1
            },
            sum: {
                $sum: {
                    $add: ["$P31", "$P32"]
                }
            }
        }
    }
])
</code></pre>

<p>I do this query from java, and I want to map it on my class, but I don't want '_id' to be mapped on 'name' field. Because if I do something like this:</p>

<pre><code>@JsonProperty("_id")
private String name;
</code></pre>

<p>then when I save this data back to mongo (after some modification) the data is saved with name as '_id' while I want a real Id to be generated.</p>

<p>So, how can I rename '_id' after $group operation?</p>
