java - MongoDB : find matching elements in an array with given attributes using java driver

Question

试图将我的游戏迁移到 mongodb (linux-i686-2.4.6) 但到目前为止有很多困难:(一个是那个；我有一个名为 gamesTable 的集合，其中包含以下元素，我想在 playerHistories 数组中进行搜索。

{
"_id": {
    "$oid": "52307b8fe4b0fc612dea2c70"
},
"id": "52307b8fe4b0fc612dea2c70", "name": "poker", "initTime": 1378909071070, "startTime": 1378909071098, "endTime": 1378909071134,
"playerHistories": [
    {
        "playerId": "52307b8fe4b0fc612dea2c6e",
        "time": 1378909071098,
        "event": "EnteredGame"
    } ,
    {
        "playerId": "52307b8fe4b0fc612dea2c6f",
        "time": 1378909071098,
        "event": "EnteredGame"
    } ,
    {
        "playerId": "52307b8fe4b0fc612dea2c6f",
        "time": 1378909071117,
        "event": "LostGame"
    } ,
    {
        "playerId": "52307b8fe4b0fc612dea2c6e",
        "time": 1378909071128,
        "event": "WonGame"
    }
]
},
{
"_id": {
    "$oid": "52307b8fe4b0fc612dea2c71"
}, "id": "52307b8fe4b0fc612dea2c71", "name": "poker", "initTime": 1378909071150, "startTime": 1378909071165, "endTime": 1378909071189,
"playerHistories": [
    {
        "playerId": "52307b8fe4b0fc612dea2c6e",
        "time": 1378909071165,
        "event": "EnteredGame"
    } ,
    {
        "playerId": "52307b8fe4b0fc612dea2c6f",
        "time": 1378909071165,
        "event": "EnteredGame"
    } ,
    {
        "playerId": "52307b8fe4b0fc612dea2c6e",
        "time": 1378909071176,
        "event": "LostGame"
    } ,
    {
        "playerId": "52307b8fe4b0fc612dea2c6f",
        "time": 1378909071183,
        "event": "WonGame"
    }
]
}

我想找到玩家赢得的游戏，在我们的示例中是；

{ "playerHistories.playerId" : "52307b8fe4b0fc612dea2c6f" , "playerHistories.event" : "WonGame"}}

我读到我应该使用 $elemMatch 来匹配数组中的元素，但是它什么都不返回:(

这是我使用的代码

    BasicDBObject elemMatch = new BasicDBObject();
    elemMatch.put("playerHistories.playerId", player1.getId());
    elemMatch.put("playerHistories.event", "WonGame");
    BasicDBObject foo = new BasicDBObject();
    foo.put("$elemMatch", elemMatch);
    gamesTable.find(foo);

我做错了什么？

Answer 1

感谢 parvin，我发现它改变了他的解决方案。

    DBObject statusQuery = new BasicDBObject("event", "WonGame");
    statusQuery.put("playerId", "52307b8fe4b0fc612dea2c6f");
    DBObject fields = new BasicDBObject("$elemMatch", statusQuery);
    DBObject query = new BasicDBObject("playerHistories",fields);
    gamesTable.find(query);