MangoDB在java中的查询

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前言

MongoDB的java驱动提供了查询的功能，查询条件也是bson对象，这篇就看下怎么进行简单的数据查询

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、查询name为user1的对象

查询条件Json内容：

{"name": "user1"}

查询条件Java内容：

BasicDBObject queryObject = new BasicDBObject("name","user1");

执行过程：

DBObject obj = collection.findOne(queryObject);

这样就拿到了name为user1的对象了

4、查询name包含user的对象

这样模糊查询，也就类似于like查询是通过正则表达式来完成的

查询条件Json内容：

{“name”:/user/}

查询条件Java内容：

Pattern queryPattern = Pattern.compile("user", Pattern.CASE_INSENSITIVE);

BasicDBObject queryObject = new BasicDBObject("name",queryPattern);

执行过程：

Pattern queryPattern = Pattern.compile("user", Pattern.CASE_INSENSITIVE);

BasicDBObject queryObject = new BasicDBObject("name",queryPattern);

Cursor cursor = collection.find(queryObject);

while(cursor.hasNext()){

DBObject obj = cursor.next();

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

}

5、查询年龄大于24的对象

查询条件Json内容：

{"age":{"$gt":24}}

查询条件Java内容:

两个Bson对象嵌套

BasicDBObject gt = new BasicDBObject("$gt",24);

BasicDBObject queryObject = new BasicDBObject("age",gt);

执行过程：

BasicDBObject gt = new BasicDBObject("$gt",24);

BasicDBObject queryObject = new BasicDBObject("age",gt);

Cursor cursor = collection.find(queryObject);

while(cursor.hasNext()){

DBObject obj = cursor.next();

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

}

备注：

$gt：>

$gte：>=

$eq: =

$ne: !=

$lt: <

$lte: <=

$in: in(后面的值为bson对象数组)

$nin: not in(后面的值为bson对象数组)

6,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());

}

7、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());

}

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