java mongodb 数组查询_Mongodb：查询嵌套在数组中的json对象

小编典典

使用位置运算符

db.test.find(

{ "array.value": "value2" },

{ "array.$": 1, _id : 0 }

)

输出量

{ "array" : [ { "name" : "test2", "value" : "value2" } ] }

使用聚合

db.test.aggregate([

{ $unwind : "$array"},

{ $match : {"array.value" : "value2"}},

{ $project : { _id : 0, array : 1}}

])

输出

{ "array" : { "name" : "test2", "value" : "value2" } }

使用Java驱动程序

MongoClient mongoClient = new MongoClient(new ServerAddress("localhost", 27017));

DB db = mongoClient.getDB("mydb");

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

DBObject unwind = new BasicDBObject("$unwind", "$array");

DBObject match = new BasicDBObject("$match", new BasicDBObject(

"array.value", "value2"));

DBObject project = new BasicDBObject("$project", new BasicDBObject(

"_id", 0).append("array", 1));

List pipeline = Arrays.asList(unwind, match, project);

AggregationOutput output = collection.aggregate(pipeline);

Iterable results = output.results();

for (DBObject result : results) {

System.out.println(result.get("array"));

}

输出

{ "name" : "test2" , "value" : "value2"}

2020-07-27