我正在尝试使用 MongoDB java 驱动程序 (3.0) 执行简单的聚合操作。需要有关如何使用 JAVA API 编写以下 mongo shell 查询的帮助。
db.coll.aggregate([
{ $project: {
email_id: { $ifNull: [ "$email_id", " " ] },
phone_num: { $ifNull: [ "$phone_num","NA" ] },
id : 1,
firstname :1,
lastname :1,
status : 1
}
},
{ $match: { status: "true"} },
{ "$group": {
"_id": "$id",
"details": { "$push": {
"$concat": [ "$firstname", " ", "$lastname", " | ", "$email_id" , " | ", "$phone_num" ]
}}
}}
])
最佳答案
这是您的 shell 查询的 java 驱动程序查询
MongoClient mongo = new MongoClient();
MongoDatabase database = mongo.getDatabase("your_database");
Document emailIdDoc = new Document("$ifNull",Arrays.asList("$email_id", " "));
Document phoneNumDoc = new Document("$ifNull", Arrays.asList("$phone_num", "NA"));
Document projectDoc = new Document("$project" , new Document("email_id", emailIdDoc).append("phone_num", phoneNumDoc).append("id" , 1).append("firstname" , 1).append("lastname", 1).append("status", 1));
Document matchDoc = new Document("$match", new BasicDBObject("status", "true"));
Document groupDoc = new Document("$group", new Document("_id", "$id").append("details", new Document("$push", concat)));
AggregateIterable<Document> aggregationResult = db.getCollection("your_collection").aggregate(asList(projectDoc, matchDoc, groupDoc));
使用弃用的方法
MongoClient mongo = new MongoClient();
DB db = mongo.getDB("your_database");
BasicDBObject emailId = new BasicDBObject("$ifNull",Arrays.asList("$email_id", " "));
BasicDBObject phoneNum = new BasicDBObject("$ifNull", Arrays.asList("$phone_num", "NA"));
DBObject project = new BasicDBObject("$project" , new BasicDBObject("email_id", emailId).append("phone_num", phoneNum).append("id" , 1).append("firstname" , 1).append("lastname", 1).append("status", 1));
DBObject match = new BasicDBObject("$match", new BasicDBObject("status", "true"));
DBObject concat = new BasicDBObject("$concat", Arrays.asList( "$firstname", " ", "$lastname", " | ", "$email_id" , " | ", "$phone_num"));
Document concatDoc = new Document("$concat", Arrays.asList( "$firstname", " ", "$lastname", " | ", "$email_id" , " | ", "$phone_num"));
DBObject group = new BasicDBObject("$group", new BasicDBObject("_id", "$id").append("details", new BasicDBObject("$push", concat)));
AggregationOutput iterable = db.getCollection("your_collection").aggregate(project, match, group);
关于java - 如何使用 MongoDB 3.0 java 驱动程序执行聚合,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/34492054/