我正在使用Mongo java驱动程序从mongo集合中检索数据。我有以下查询,我试图在java中实现: Json是:
{
"_id" : ObjectId("56cd284767c74d3d4dd3ec80"),
"comments" : "Hello",
"statusLog" : [
{
"status" : "Submitted",
"startDate" : ISODate("2015-01-14T05:00:00.000Z"),
"endDate" : ISODate("2016-02-29T21:24:24.740Z")
},
{
"status" : "Active",
"startDate" : ISODate("2016-02-29T21:24:24.740Z")
}
],
"createdDate" : ISODate("2015-01-14T05:00:00.000Z")
}
Mongo查询:
db.CollectionName.find({},{_id: 0, createdDate:1, "statusLog": {$elemMatch: {"status":"Submitted"}}});
以下是我编写的java中的查询(mongo java driver 3.4.2):
BasicDBObject query = new BasicDBObject(new BasicDBObject("statusLog",
new BasicDBObject("$elemMatch", new BasicDBObject("status", "Submitted"))));
运行java代码会返回所有状态日志,而不是我要查找的日志。
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答案 0 :(得分:3)
您应该使用较新的Document/MongoCollection
api并使用辅助方法来准备投影。
import static com.mongodb.client.model.Filters.eq;
import static com.mongodb.client.model.Projections.*;
MongoClient mongoClient = new MongoClient();
MongoDatabase database = mongoClient.getDatabase("db"); // Get DB
MongoCollection<Document> collection = database.getCollection("collection"); // Get Collection
Bson projection = Projections.fields( excludeId(), include("createdDate"), elemMatch("statusLog", eq("status", "Submitted"))); // Add Projections
FindIterable<Document> iterable = collection.find().projection(projection);
使用旧BasicDBObject/DBCollection
api
MongoClient mongoClient = new MongoClient();
DB database = mongoClient.getDB("db");
DBCollection collection = database.getCollection("collection");
BasicDBObject projection = new BasicDBObject(new BasicDBObject("statusLog",new BasicDBObject("$elemMatch", new BasicDBObject("status", "Submitted"))));
collection.find(new BasicDBObject(), projection);
答案 1 :(得分:1)
接受的答案是错误的。 <h2>
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</h2>
应该在find方法中而不是在投影bson中。例如:
elemMatch