mongo数组上的where子句不起作用

Question

我是mongodb的新手，在数据库中有一个文档，如下所示：

{“ _id”：{“ $ oid”：“ 546e916cd38e0b3e0e79592f”}，“ name”：“ hamed”，“ entity”：[“ 1”，“ 2”]}

现在，我想阅读ental = [“ 1”，“ 2”]的Aal文档，因为我尝试了以下代码：

MongoClient mongoClient = new MongoClient("localhost", 27017);
    DB db = mongoClient.getDB("test");
    Set<String> colls = db.getCollectionNames();
    DBCollection coll = db.getCollection("test");
    DBObject oredrFields = new BasicDBObject();
    oredrFields.put("entity", ":{ $in: ['1', '2'] } }");
    DBCursor cursor = coll.find(oredrFields);
    try {
        while (cursor.hasNext()) {
            System.out.println(cursor.next());
        }
    } finally {
        cursor.close();
    }

但是它什么也不会返回...谁能帮助我正确编写where子句？

Answer 1

$ in也应该是BasicDBObject：

DBObject oredrFields = new BasicDBObject();
DBObject inOp = new BasicDBObject();
inOp .put("$in", new String[]{"1","2"});
oredrFields.put("entity", inOp);

Answer 2

您需要将查询参数作为DBObject 。 您缺少$in运算符的DBObject 。

如果只想要同时具有“ 1”和“ 2”的记录，则需要使用$all而不是$in ，它仅返回entity字段包含所传递数组中all元素的那些文档。

    MongoClient mongoClient = new MongoClient("localhost", 27017);
    DB db = mongoClient.getDB("test");
    DBCollection coll = db.getCollection("test");
    DBObject oredrFields = new BasicDBObject();
    DBObject inQuery = new BasicDBObject().append("$all", new String[]{"1","2"});
    oredrFields.put("entity", inQuery);
    DBCursor cursor = coll.find(oredrFields);
    try {
        while (cursor.hasNext()) {
            System.out.println(cursor.next());
        }
    } finally {
        cursor.close();
    }