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