Spring Data MongoDB 中的上限数组

Question

I'm new to Spring Data MongoDB and wondering if you could help me. Basically, what I want to achieve is to limit the size of an embedded array in my document. I've seen other post but it's not using the spring data mongodb ( Saving with Java springdata a mongoDB document with capped array ($slice and $sort) , MongoDB 2.4's "Limit Number of Elements in an Array after an Update" using C# driver? ).

Sample Document:
{

  _id: 1,
  scores: [
     { attempt: 1, score: 10 },
     { attempt: 2 , score:8 }
         ]
}

updateScore() { Query query = new Query(Criteria.where("id").is(id)); query.fields().slice("scores", -3); Update update = new Update(); update.push("scores", scores); mongoOperations.findAndModify(query, update, MyDocument.class); } updateScore() { Query query = new Query(Criteria.where("id").is(id)); query.fields().slice("scores", -3); Update update = new Update(); update.push("scores", scores); mongoOperations.findAndModify(query, update, MyDocument.class); } After calling updateScore method, I could see that new scores were appended and it's size exceeds 3.

     <!-- mongodb java driver -->
    <dependency>
        <groupId>org.mongodb</groupId>
        <artifactId>mongo-java-driver</artifactId>
        <version>2.13.0</version>
    </dependency>

    <!-- Spring data mongodb -->
    <dependency>
        <groupId>org.springframework.data</groupId>
        <artifactId>spring-data-mongodb</artifactId>
        <version>1.5.4.RELEASE</version>
    </dependency>

Hope to hear your comments and suggestion.

Answer 1

You could change your update to something like this:

Query query = new Query(Criteria.where("id").is(id));
query.fields().slice("scores", -3);
Update update = new Update();
update.push("scores", scores);
update.push("scores", new BasicDBObject("$each", scores).append("$slice", -3));
mongoOperations.findAndModify(query, update, MyDocument.class);

$slice within within a push is not yet supported by spring-data -> https://jira.spring.io/browse/DATAMONGO-832

Answer 2

update.push("scores").slice(-3).each(scores)