Implementing aggregation in Mongo using a Java client
The intention of this recipe is not to explain aggregation but to show you how aggregation can be implemented using the Java client from a Java program. In this recipe, we will aggregate the data based on the state names and get the top five state names by the number of documents that they appear in. We will use the $project, $group, $sort, and $limit operators for the process.
Getting ready
The test class used for this recipe is com.packtpub.mongo.cookbook.MongoAggregationTest. To execute the aggregation operations, we need to have a server up and running. A simple single node is what we need. Refer to the Installing single node MongoDB recipe from Chapter 1, Installing and Starting the Server ...
Get MongoDB Cookbook - Second Edition now with the O’Reilly learning platform.
O’Reilly members experience books, live events, courses curated by job role, and more from O’Reilly and nearly 200 top publishers.
