java MongoDB查询（二）复杂查询

前言

        在上篇《java MongoDB查询（一）简单查询》中我们简单了解了下查询，但是仅仅有那些查询是不够用的，还需要复杂的查询，这篇就这点进行叙述。

1、数据结构

        集合：firstCollection

        数据内容：

        { "_id" : ObjectId("55adba52fa1f3cf038c2aea6"), "name" : "user0", "age" : 22, "sex" : 0 }

        { "_id" : ObjectId("55adba52fa1f3cf038c2aea7"), "name" : "user1", "age" : 23, "sex" : 1 }

        { "_id" : ObjectId("55adba52fa1f3cf038c2aea8"), "name" : "user2", "age" : 24, "sex" : 0 }

        { "_id" : ObjectId("55adba52fa1f3cf038c2aea9"), "name" : "user3", "age" : 25, "sex" : 1 }

        { "_id" : ObjectId("55adba52fa1f3cf038c2aeaa"), "name" : "user4", "age" : 26, "sex" : 0 }

        { "_id" : ObjectId("55adba52fa1f3cf038c2aeab"), "name" : "user5", "age" : 27, "sex" : 1 }

2、连接数据库，拿到集合firstCollection

        MongoClient mClient = new MongoClient("10.211.55.8");

        DB db = mClient.getDB("test");

        DBCollection collection = db.getCollection("firstCollection");

3、与查询

        操作符：$and

        场景：查询age大于23，并且sex为1的对象

        查询条件Json内容：

        {"$and":[{"age":{"$gt":23}},{"sex":1}]}

        查询条件Java内容:

        BasicDBObject ageObj = new BasicDBObject("age",new BasicDBObject("$gt",23));

        BasicDBObject sexObj = new BasicDBObject("sex",1);

        BasicDBObject andObj = new BasicDBObject("$and",Arrays.asList(ageObj,sexObj));

        执行过程：

        Cursor cursor = collection.find(andObj);

        while(cursor.hasNext()){

                DBObject obj = cursor.next();

                System.out.println(obj.toString());

        }

4、或查询

        操作符：$or

        场景：查询name为user2，或者name为user3的对象

        查询条件Json内容：

        {"$or":[{"name":"user2"},{"name":"user3"}]}

        查询条件Java内容：

        BasicDBObject user2Obj = new BasicDBObject("name","user2");

        BasicDBObject user3Obj = new BasicDBObject("name","user3");

        BasicDBObject orObj = new BasicDBObject("$or",Arrays.asList(user2Obj,user3Obj));

        执行过程：

        Cursor cursor = collection.find(orObj);

        while(cursor.hasNext()){

                DBObject obj = cursor.next();

                System.out.println(obj.toString());

        }

5、总结

        通过与或的查询，我们了解了查询条件组合的方式，通过这种方式，再联系上篇《java MongoDB查询（一）简单查询》内容就可以组合成我们想要的各种结果的查询条件了