前言
在上篇《java MongoDB查詢（一）簡單查詢》中我們簡單了解了下查詢，但是僅僅有那些查詢是不夠用的，還需要復雜的查詢，這篇就這點進行敘述。
1、數據結構
集合：firstCollection
數據內容：
{ "_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、連接數據庫，拿到集合firstCollection
MongoClient mClient = new MongoClient("10.211.55.8");
DB db = mClient.getDB("test");
DBCollection collection = db.getCollection("firstCollection");
3、與查詢
操作符：$and
場景：查詢age大於23，並且sex為1的對象
查詢條件Json內容：
{"$and":[{"age":{"$gt":23}},{"sex":1}]}
查詢條件Java內容:
BasicDBObject ageObj = new BasicDBObject("age",new BasicDBObject("$gt",23));
BasicDBObject sexObj = new BasicDBObject("sex",1);
BasicDBObject andObj = new BasicDBObject("$and",Arrays.asList(ageObj,sexObj));
執行過程：
Cursor cursor = collection.find(andObj);
while(cursor.hasNext()){
DBObject obj = cursor.next();
System.out.println(obj.toString());
}
4、或查詢
操作符：$or
場景：查詢name為user2，或者name為user3的對象
查詢條件Json內容：
{"$or":[{"name":"user2"},{"name":"user3"}]}
查詢條件Java內容：
BasicDBObject user2Obj = new BasicDBObject("name","user2");
BasicDBObject user3Obj = new BasicDBObject("name","user3");
BasicDBObject orObj = new BasicDBObject("$or",Arrays.asList(user2Obj,user3Obj));
執行過程：
Cursor cursor = collection.find(orObj);
while(cursor.hasNext()){
DBObject obj = cursor.next();
System.out.println(obj.toString());
}
5、總結
通過與或的查詢，我們了解了查詢條件組合的方式，通過這種方式，再聯系上篇《java MongoDB查詢（一）簡單查詢》內容就可以組合成我們想要的各種結果的查詢條件了