I am working on a multi-country application where I have different db schemas for each country. I want to understand how can i call a different query file based on the country a user belongs to.. One way i thought of was maintaining different query files for different countries (IqueryConstantsIndia, IQueryConstntChina etc) and to check the country of the user in the constructor of the repository class and then call the query file based on the same but how do i return a class name is what i am stuck with.. Can anyone help on this or if you think there is a better way of implementing this.
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I've seen a lot of information on the different inheritance strategies but can't seem to find anything on how you setup a REST controller when using a single table strategy. In my scenario, I have 2 Barcode types: product and case.
I created a Barcode superclass that ProductBarcode and CaseBarcode inherit from. However, I have the following questions regarding how to implement this:
Do I need separate repositories for ProductBarcode and CaseBarcode?
Can I use a single endpoint to create/update/delete both kinds of Barcodes?
I have another entity (Product) that relates to Barcode and needs to be able to get the details for a barcode based on an ID. Product won't know what type of Barcode the ID belongs to. Is this something that will cause an issue?
To summarize what I'm trying to do:
Create a barcode entry of either ProductBarcode or CaseBarcode by sending a JSON POST request to a single endpoint such as localhost:8080/barcodes.
Retrieve or update a barcode of either type from a single endpoint.
Be able to perform CRUD operations without needing to know which type of Barcode is being operated on.
Is this something that is doable using Spring Data JPA and Hibernate? Thanks for any advice.
I'm trying to write microservices in Java. I've implemented GraphQL endpoints using graphql-spring-boot-starter.
Now I have a problem how to make it efficient.
Datamodel is like a tree and I need to query for data from multiple services at once. The problem is how to filter for a member of collection, something like CONTAINS in database, but data is not in separate table, but separate microservice. Maybe the problem is that domain is not correctly splitted between services?
Let's make an example: I have 3 microservices: users, libriaries, books. Every library have collection of users and books (just list of identifiers, like foreign keys). Every book has a name and genre. Every library have lists of books borrowed by user (identifiers too).
Question 1 - should library hosts list of books and users (just identifiers, like foreign keys)? Is it correct approach?
Question 2 - I want to find libraries in which specified users (by surname) have borrowed books of specified genre. Going from top I need to first find libraries containing users. Not easy, as we have names in different service. We need to query first for users, gathers their identifiers, and now we are able to query for libraries. But it isn't all. Now we need to find books for every user and check genres - in different service. And it's not all. I want to have everything presented in nice way, so whole output should be sorted and paged. It force me to collect all data from all services, then page and sort it, which of course will not be efficient.
Please don't concentrate on this example, I'm looking how to solve general approach, not this one example. I've tried to use Datafetchers but it's troublesome and there are not good examples of calling Graphql-to-GraphQL. Most examples covers calling REST endpoints etc.
I'm making a system (using Spring + JPA with MySQL) that shows the best applicants for a certain job offer. The company and the applicants have their respective user account, and with that, they can fill in their personal/company information and their job profile/job offer conditions. With that, the system should match the job conditions (like 3+ years of experience in C) with the applicant's job profile.
My problem is that the User Account is created first, and should be independent, but these two different entities (Applicant and Company), with different attributes, are using it. So if I do something like create an applicant and company in the User Account, one of them will be always null.
How can I solve this? I guess the problem would be something like: how to implement a user account that can hold data from different entities that have different attributes (therefore, can't be grouped)? (In fact, I need one more entity, but I tried to simplify it to illustrate the problem more clearly).
I think, you should make marker interface, like public interface UserAccountable or smth. Implement this interface in your Applicant and Company classes. Then you can make a field in UserAccount class, like private UserAccountable someUser; and throught setters and getters you can assign and get this variable to Applicant or Company.
Hope this helps!
I found what I needed here: https://thoughts-on-java.org/complete-guide-inheritance-strategies-jpa-hibernate/
The problem was the mapping, not the class design per se. I could create interfaces and abstract classes to solve it in the Java world, but in the SQL world that's not possible, so the mapping is the key. In this case, I was looking for the Joined table mapping, but I realized I needed it just to not have null fields in my UserAccount, because I don't need a polymorphic query (e.g. give me the names of every 'user type' (Person, Company)), and it would be too costly performance wise to implement it that way, so I'll trade off space for performance, and I'll just reference all three user types in the User Account, leaving two of those three fields null forever.
PS: Single table mapping won't help because I do need to use not null conditions.
I'm having trouble figuring out a data model for my project. I'm using Parse as the backend.
I intend to have users who are in groups, and the groups have text posts. What should be classes, and what should be rows in those classes.
I'm guessing a good way to do this would be, have a group, user, and post class.
The columns for the group class would be: GroupID, GroupName, postID, UserID
The columns for the user class would be: UserID, GroupsUserBelongsTo, user name, password, email
The columns for the post class would be: UserIDPostBelongsTo, GroupID, TextFile, TimeCreated
Is there anything I'm missing, or I should change.
You're thinking is a very SQL / rows based way and you shouldn't, this isn't SQL, it's objects and relationships.
So, your classes are fine, and the actual data is fine, but where you're using ids you should be using relationships. Post should just have a pointer to user. Perhaps, don't bother with a relationship from user to groups (you can query that using the other relationship), though you can, particularly if you will have lots of users / groups.
You may also want to consider roles to provide security for the groups.
I have 2 models, one called Employee and another one User,
Employee has one field pointing to User, one to one relationship.
My problem is that i need one query method to find the Employee that has the user with certain id. I need to find the Employee with certain User id.
I know the default query methods: .findOne, .findAll, but i need to create one, alright? how i can do that? i searched a lot but probably i am missing something. I didn't found how to do a query like that.
Thanks