[FIXED] Using Spring Data JPA with an adjacency matrix stored in a MySQL database

Issue

I am new to using Spring Data Jpa but I understand one normally creates a 'Model'/ 'Entity' class in Java that represents a row of data in your database table. This makes sense to me when I have a small table with 3 columns/ class attributes, but what about the case of a table with 100 columns? One hardly creates a 'Model' class with 100 attributes? The reason I ask this is because I am storing a large adjacency matrix of train stations in a MySQL database table. I want to interact with this data in my Java Spring application but cannot get my head around how to do this.

I am open to the fact that I may be storing the data incorrectly or should not be using Spring Data JPA at all in this situation. Any advice would be greatly appreciated!

Thanks.

EDIT:

I'll try to explain what I'm trying to do more clearly. I would like to essentially import a copy of this 'Stations' (adjacency matrix) database table into my Java Spring application. I don't know how best to perform this 'import', or what Java data structure to store the table in. I would like to be able to run algorithms like BFS on the data once in Java.

The data in the table is an adjacency matrix showing a graph of a train network. A '1' shows the stations are connected by a track and a '0' shows no connection.

Solution

Representing it as a many to many relationship could work well in this case. I'm not very familiar with JPA but I think it would look something like this:

@Getter
@Setter
@Entity
public class Station {

    @Id    
    private Long id;

    private String name;

    @ManyToMany       
    private Set<Station> adjacentStations;
}

The stations are interconnected, such that when station B is adjacent to station A (i.e. B is in A's set of adjacent stations), then station A is also adjacent to station B (i.e. A is also in B's set of adjacent stations).

In the database, the relationship between stations would then be represented through a mapping table that has two columns (station_id_1, station_id_2) and one row for each connection.

Answered By - alsed42