MongoDb Java驱动程序v3.x和聚合框架

Question

我有一个包含联系人的集合，每个联系人文档都有firstname和lastname属性。

现在我想使用Java和版本3.2中的MongoDb Java驱动程序查询数据库。

db.getCollection('contacts').aggregate(
     {
           $project:{
                fullName:{
                   $concat: [ "$firstName", " ", "$lastName" ]
                }
            }
      },
      {
            $match:{
                fullName:"John Doe"
            }
       }
);

AggregateIterable<Document> documents = contactUserCollection.aggregate(Arrays.asList(project(computed("fullName", "$firstName $lastName")), match(eq("fullName", firstLastName))));

谢谢。

Answer 1

您可以尝试以下方法：

/*
    MONGO SHELL : 
    var pipeline = [         
        { 
            "$project": { 
                "otherfieldsA": 1, 
                "otherfieldsB": 1, 
                "otherfieldsC": 1, 
                "fullName": { 
                    "$concat": [ "$fistName", " ", "$lastName" ] 
                } 
            } 
        } 
        { 
            "$match": { "fullName": "John Doe" }
        }
    ];
    db.contacts.aggregate(pipeline);

*/

public class JavaAggregation {
    public static void main(String args[]) throws UnknownHostException {

        MongoClient mongo = new MongoClient();
        DB db = mongo.getDB("test");

        DBCollection coll = db.getCollection("contacts");

        // create the pipeline operations, build the $project operations
        BasicDBList concatenate = new BasicDBList();
        concatenate.add("$firstName");
        concatenate.add(" ");
        concatenate.add("$lastName");

        DBObject fullName = new BasicDBObject("$concat", concatenate);

        DBObject fields = new BasicDBObject("otherfieldsA", 1);
        fields.put("otherfieldsB", 1);
        fields.put("otherfieldsC", 1);
        fields.put("fullName", fullName);

        DBObject project = new BasicDBObject("$project", fields);

        // create the $match operator
        DBObject match = new BasicDBObject("$match",
                            new BasicDBObject("fullName", "John Doe")
                         );
        AggregationOutput documents = coll.aggregate(match, project, group, sort);

        for (DBObject result : documents.results()) {
            System.out.println(result);
        }
    }
}