How do I populate a Vaadin 12.0.4 Grid with data/fields from a PostgreSQL 10.5 table or view?

I know there are dozens of tutorials for how to do this across just as many websites, but this is my first time trying to connect a database table to a UI, so when the version of Spring Boot/MyBatis/Vaadin, for example, are different than the one I'm working with, or they use JPA or JDBC instead of MyBatis, I have no idea how to change it to work with my specific situation.

When people say "it's no different than any other method of doing it with " that doesn't help AT ALL, since, as I stated earlier, I've never done it before. Annotations and classes in the code examples of a tutorial get removed and deprecated with every new version with no clear explanation of how to change it to work with the newer version. I've been researching the various APIs (Spring Boot, Vaadin, MyBatis) for about a month and have a vague understanding of what each one does but not how they work together to achieve the desired result of making a UI for a database. I'm just getting really frustrated at how a single deprecated annotation or class in a tutorial can bring the whole thing crashing down. I know that was long-winded but I just wanted you all to understand where I'm coming from. I'm not particularly attached to any single API, just whatever is easiest.

My current dependencies are:

- Maven : 4.0.0 - Spring Boot: 2.1.2.RELEASE - Vaadin: 12.0.4 - MyBatis Spring Boot Starter: 2.0.0

I got the starter package from Spring Initializr and added the MyBatis dependency later.

I have a PostgreSQL 10.5 database with 17 tables that will eventually be a UI for a store manager to use for things like looking at received inventory shipments, the hours an employee worked, and other tasks.

My database is named 'store', user: 'store', password: 'store' (if it matters).

For example, these are a few of my tables:

CREATE TABLE IF NOT EXISTS supplier ( id SERIAL, brand VARCHAR(30) NOT NULL, phone VARCHAR(15) NOT NULL, address VARCHAR(100) NOT NULL, CONSTRAINT pk_supplier PRIMARY KEY (id) );

CREATE TABLE IF NOT EXISTS shipment ( id SERIAL, shipdate DATE NOT NULL, shiptime TIME NOT NULL, status VARCHAR(10) DEFAULT 'arrived' NOT NULL, sid INT NOT NULL, CONSTRAINT pk_shipment PRIMARY KEY (id), CONSTRAINT fk_shipment_supplier FOREIGN KEY (sid) REFERENCES supplier(id) );

CREATE TABLE IF NOT EXISTS shipmentcontains ( shipid INT NOT NULL, iid INT NOT NULL, quantity INT NOT NULL, price DEC(6,2) NOT NULL, CONSTRAINT pk_shipmentcontains PRIMARY KEY (shipid, iid), CONSTRAINT fk_shipmentcontains_shipment FOREIGN KEY (shipid) REFERENCES shipment(id), CONSTRAINT fk_shipmentcontains_item FOREIGN KEY (iid) REFERENCES item(id) );

CREATE TABLE IF NOT EXISTS item ( id SERIAL, itemtype VARCHAR(25) NOT NULL, itemsize VARCHAR(10) NOT NULL, price DEC(5,2) NOT NULL, sid INT NOT NULL, CONSTRAINT pk_item PRIMARY KEY (id), CONSTRAINT fk_item_supplier FOREIGN KEY (sid) REFERENCES supplier(id) );

CREATE TABLE IF NOT EXISTS employee ( id SERIAL, lastname VARCHAR(40) NOT NULL, firstname VARCHAR(40) NOT NULL, hourlywage DEC(4,2), manager BOOLEAN DEFAULT false NOT NULL, CONSTRAINT pk_employee PRIMARY KEY (id) );

If someone can give me a code example of how to just get one of those to show in a Grid, I'm sure I can figure out how to do the rest of it. I have the connection details in my application.properties file, but I've seen that with newer versions of MyBatis this isn't needed and annotations such as @Update can be used on the SQL statements to replace that. Also, in plain English, what the heck is a Spring Bean? I hope that wasn't too long..or not long enough.

EDIT: Current version of Vaadin 12 is 12.0.4

You are asking quite a lot, so I will try to touch everything a little and nothing too detailed. I hope this helps you getting the ball rolling.

First off, you will need a java class with all fields that you have in the supplier table, annotated with @Entity. The @Table annotation lets you define the Db table name, and it is not necessary if the table is called the same as the class (case insensitive):

@Entity                        // javax.persistence
@Table(name = "supplier")      // javax.persistence
public class Supplier {

    @Id                        // javax.persistence
    private Long id;

    private String brand;
    private String phone;
    private String address;

    public Supplier(){

    }

    // public getters and setters for all fields
    // omitted for brevity
}

Now that you have a class for your table, you can start with creating a Vaadin Grid for it. This can be done the easiest with Grid<Supplier> supplierGrid = new Grid<Supplier>(Supplier.class);.

Now to fill the grid with items (suppliers). This is done with supplierGrid.setItems(allSuppliers);. But where do allSuppliers come from you ask?

They can be fetched using a Repository. Because the repository will be annotated with @Repository, its a spring component that can be automatically generated by spring and can be Injected/Autowired (i.e. in your view) using @Inject/@Autowired.
Then you simply call List<Supplier> allSuppliers = supplierRepository.findAll() and you have a list of all suppliers from your DB, that you now can put into the grid with the aforementioned supplierGrid.setItems(allSuppliers);

Any class where an instance of it can be injected by spring is a spring-bean, this includes classes annotated with either @Component, @Serivce or @Repository. Entities like Supplier can not automatically be injected by Spring, unless you define this is your @Configuration class:

/* Do this only if you want to inject a Supplier somewhere. */
@Bean
public Supplier supplier(){
    /* define here how a default Supplier should look like */
    return new Supplier();
}