Question 115355 in Mongodb Question posted in
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How to save one document or a file permanently inside collection of MongoDB with Springboot

all! I’m working on a project with MongoDB and Spring Boot. I want to implement a feature so that once I start running the server, there will be a fixed item (or file) stored in the collection of the MongoDB database. I want to forbid remove operation for this collection from application. How could I achieve this function? If there is any ambiguity, please let me know.

Here is an example. Let’s say that there is a collection called Node. This is the schema:

{
    "id": "xxxx",
    "value": "1",
    "left": "left_node",
    "right": "right_node"
}

I want to keep this data in the database once the server started.

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2

Answers


  1. 0

    anything can be removed within a database. but you can manage that by create separate users with different roles/privileges when accessing the database. ref: create-a-user-defined-role

    but you can do it manually where you need to check the _id|id before or within operation delete,

    ex:

    db.document.delete({id: {$ne: 'xxxx'}}}
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  2. 0

    Assuming, you’re using Spring Data Mongo, if you need to forbid delete operations on your collection, you can create a special repository interface and inherit the repository bean for that collection from that repository interface.

    Declare a generic repository which allows only save() operation:

    @NoRepositoryBean
public interface SaveOnlyRepository<T, ID> extends Repository<T, ID> {

    <S extends T> S save(S entity);
}

    Note: Dont forget to annotate this generic repository with @NoRepositoryBean which is used to avoid creating repository proxies for interfaces that actually match the criteria of a repo interface but are not intended to be one.

    And extend your repository bean for that collection from that interface. Also add a existsByValue() method for further checking during the application startup.

    public interface NodeRepository extends SaveOnlyRepository<Node, String> {

    boolean existsByValue(String value);
}

    Then you can create a listener that listens for ApplicationReadyEvent

    Within this listener you can check if the Node exists. If it doesn’t, then you save a document.

    @Component
public class Listener {

    private final NodeRepository nodeRepository;

    public Listener(NodeRepository nodeRepository) {
        this.nodeRepository = nodeRepository;
    }

    @EventListener(ApplicationReadyEvent.class)
    public void init() {
        if (!nodeRepository.existsByValue("1")) {
            nodeRepository.save(...);
        }
    }
}
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