Spring Boot with Vaadin - using foreign keys - spring

Question

I am new to Spring Boot and Vaadin. I followed a tutorial to create CRUD pages for a phone book application however I am having trouble using foreign keys. I have a Contact table which has phone type (i.e. cell or home) as a foreign key - i.e. it is referenced to my PhoneType table. I am stuck on how to populate the phone type from a drop down of values populated in my PhoneType table. Right now I am I have the following member variable in my Contact class
#ManyToOne
#JoinColumn(name="type")
private PhoneType phoneType;
And in my PhoneType class I have
#Column(name = "type")
private String phoneType;
However I am getting an error that says "Error executing DDL via JDBC Statement".
The rest of the application works well with the CRUD pages.

Answer 1

Firstly in mySQL implementations you can't store actual objects unless you use 8.0+ JSON data type. SQL has no idea what a PhoneType is because it's an object and not a valid data type. https://www.w3schools.com/sql/sql_datatypes.asp
If you want to store actual objects you need to find a noSQL implementation that you like.
So your "Customer" class doesn't map to a table properly. You would need to make instance variables such as
String hasCellPhone, hasHomePhone; //etc for the options in your dropdown menu
instead of trying to put a phonetype object.
I asked almost the exact same question, I suggest you read this entire thread.
https://stackoverflow.com/a/50879597/5468597
create table item (
barcode bigint not null auto_increment primary key,
name varchar(20) not null,
type varchar(20) not null,
is_available boolean not null,
is_late boolean null,
notes varchar(255) null,
check_out_date datetime null,
due_date datetime null
#create index idx_barcode (barcode));
create table patron (
trinity_id bigint not null primary key,
name varchar(30) not null,
email varchar(20) not null,
owes_fines boolean not null,
fines_owed int null
#create index idx_trinity_id (trinity_id));
create table checked_out_items (
ref_id bigint primary key auto_increment not null,
patron_id bigint not null,
item_id bigint not null,
item_available boolean not null,
item_check_out_date datetime null,
item_due_date datetime null);
alter table checked_out_items
add constraint fk_patron_id
foreign key (patron_id) references patron(trinity_id),
add constraint fk_item_id
foreign key (item_id) references item(barcode)
#add constraint fk_item_available
#add constraint fk_check_out_date
#add constraint fk_due_date
#foreign key (item_available references item(is_available)
#foreign key (item_check_out_date) references item(check_out_date)
#foreign key (item_due_date) references item(due_date)
on update cascade
on delete cascade;
insert into patron values(0000000,'Test Erino','test#erino.edu',0,null);
insert into item values(1,'Chromebook','Laptop',0,null,null,null,null);
insert into checked_out_items(patron_id,item_id,item_available,item_check_out_date,item_due_date)
select patron.trinity_id,item.barcode,item.is_available,item.check_out_date,item.due_date
from patron
inner join item;
and lastly:
select * from item;
select * from patron;
select * from checked_out_items;
I won't post the java logic here. That's for you to read in the other thread.

Answer 2

I solved my question.
#ManyToOne (cascade = {CascadeType.ALL})
#JoinColumn(name="phoneType_typeId")
private PhoneType phoneType;
And
#Id
#GeneratedValue
#Column(name = "typeId")
private Long id;