{"id":1533,"date":"2012-07-14T15:00:00","date_gmt":"2012-07-14T15:00:00","guid":{"rendered":"http:\/\/www.javacodegeeks.com\/2012\/10\/sorting-spring-data-mongodb-collections-using-orderby.html"},"modified":"2012-10-22T06:01:37","modified_gmt":"2012-10-22T06:01:37","slug":"sorting-spring-data-mongodb-collections","status":"publish","type":"post","link":"https:\/\/www.javacodegeeks.com\/2012\/07\/sorting-spring-data-mongodb-collections.html","title":{"rendered":"Sorting Spring Data MongoDB collections using @OrderBy"},"content":{"rendered":"
This is already third post about tuning and enhancing Spring Data MongoDB<\/a> capabilities. This time I found that I miss one JPA feature \u2013 @OrderBy<\/a> annotation. @OrderBy specifies the ordering of the elements of a collection valued association at the point when the association is retrieved. <\/p>\n

In this article I will show how to implement sorting<\/strong> with @OrderBy<\/strong> annotation with Spring Data MongoDB<\/strong>.  <\/strong><\/p>\n

Use case<\/strong> <\/p>\n

Just a short example of what is it all about for those who did not use JPA @OrderBy before. We\u2019ve got here two classes and one to many relation: <\/p>\n

package pl.maciejwalkowiak.springdata.mongodb.domain;\r\n\r\nimport org.bson.types.ObjectId;\r\nimport org.springframework.data.annotation.Id;\r\nimport org.springframework.data.mongodb.core.mapping.Document;\r\n\r\n@Document\r\npublic class Backpack {\r\n @Id\r\n private ObjectId id;\r\n\r\n private List<Item> items;\r\n\r\n ...\r\n}\r\n<\/pre>\n
public class Item {\r\n private String name;\r\n private int price;\r\n\r\n ...\r\n}\r\n<\/pre>\n
Backpack is here a main class and contains list of embedded items. When Backpack is loaded from database its items are loaded in order close to insertion order. What if we want to change that and order items by one of its fields? We need to implement sorting by our own and again we will extend AbstractMongoEventListener<\/a>.         <\/p>\n
Sorting details: introducing @OrderBy<\/strong>        <\/p>\n
In opposite to JPA \u2013 sorting in this case sorting cannot be done on database level. We need to take care about it on application side \u2013 that can be done in two places:         <\/p>\n