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Mapping hibernate entity Many to one

I’m a little lost in my hibernate mapping.
I have these entity :
CommandLine :
idCommand
idCommandeLine
idItem
idStore
dateCommand
Item :
idItem
libItem
price
Store :
idStore
idWarehouse
libStore
Warehouse :
idWarehouse
libWarehouse
Stock :
idItem
idWarehouse
qtyStock
I want to add a qtyStock attribute in CommandLine.
The goal is, when I loop thought commandLines object, I can get the qtyStock of the item.
Based on the idStore, we can get the idWarehouse, and get the qty.
But how translate this in my hibernate XML Mapping ?

Don't use HBM XML mappings. The annotation mapping model is the preferred choice and you will find plenty of tutorials and help here for that model. If you really must use HBM XML mappings, we need more details. What did you try so far and did not work? How do your current mappings look like?

Error : Unique index or primary key violation in Spring Boot with the usage of Graphql?

I've implemented an example of the usage of Graphql in Spring Boot.
I got an error when I wrote the essential code snippets for both the mutation and the query variables part.
Here is my URL : http://localhost:8081/graphql
Here is my method type: POST
Here is my mutation snippet which is shown below.
mutation newHospital($hospitalInput: HospitalInput!) {
newHospital(hospital: $hospitalInput){
name
}
}
Here is my query variables snippet which is shown below.
{
"hospitalInput": {
"name": "Hospital 6"
}
}
Here is my error which is shown below.
org.h2.jdbc.JdbcSQLIntegrityConstraintViolationException: Unique index or primary key violation
Here is my project file : Project Link
How can I fix it?

You are using #GeneratedValue without specifying the concrete strategy. This resolves to #GeneratedValue(strategy=GenerationType.AUTO).
From your code
#Id
#GeneratedValue
#EqualsAndHashCode.Include
private Integer id;
Try using #GeneratedValue(strategy=GenerationType.IDENTITY)
IDENTITY Indicates that the persistence provider must assign primary
keys for the entity using a database identity column. AUTO Indicates
that the persistence provider should pick an appropriate strategy for
the particular database. TheAUTO generation strategy may
expect a database resource to exist, or it may attempt to create one.
A vendor may provide documentation on how to create such resources in
the event that it does not support schema generation or cannot create
the schema resource at runtime.

Set Hibernate access strategy globally?

According to the Hibernate documentation, the placement of the #Id annotation determines how Hibernate will access the entity (field or accessors)
As a JPA provider, Hibernate can introspect both the entity attributes (instance fields) or the accessors (instance properties). By default, the placement of the #Id annotation gives the default access strategy. When placed on a field, Hibernate will assume field-based access. Place on the identifier getter, Hibernate will use property-based access.
Is it possible to define this globally via a property (To avoid having to place a #Access(AccessType.FIELD) on each entity or embeddable)?
I found this related question, but that is for Spring Boot specifically.

You can create a file called orm.xml and put it to the classpath in directory META-INF.
In that file you can set default values. For example the access type:
<?xml version="1.0" encoding="UTF-8"?>
<entity-mappings>
<persistence-unit-metadata>
<access>PROPERTY</access>
</persistence-unit-metadata>
</entity-mappings>
You can find the XML Schema here: https://github.com/hibernate/hibernate-orm/blob/master/hibernate-core/src/main/resources/org/hibernate/jpa/orm_2_2.xsd

How to override an annotation-defined table name in JPA?

I have tables that have this annotation structure in my application and I use JpaRepository for CRUD operations.
#Entity
#Table(name = "FOO")
public class Foo implements Serializable {
…
}
But I need to override only the table name (not any of the #Column etc. attributes) from an orm.xml or properties file without changing the actual code. I've searched and I couldn't find a way to do it in Spring Data JPA. Am I missing something here or it is not supported?

Firstly, Spring Data is not a JPA provider but simply a 'helper' library providing a wrapper round common persistence operations. The JPA specification however does provide a mechanism for overriding annotations via an XML mapping file. So assuming your provider (Hibernate, EclipseLink, OpenJPA or whatever) fully implements the JPA specification then you should be able to do this.
However it would appear that you cannot override only the table name: unless your column names are mapped to the default values then, as far as I can see, you need to specify each column in the mapping file - which is slightly inconvenient I suppose.
The book Pro JPA 2 : Mastering the Java Persistence API notes:
The metadata-complete attribute is an attribute on the entity,
mapped-superclass, and embeddable elements. If specified, all
annotations on the specified class and on any fields or properties in
the class will be ignored, and only the metadata in the mapping file
will be considered as the set of metadata for the class. When
metadata-complete is enabled, the same rules that we applied to
annotated entities will still apply when using XML-mapped entities.
For example, the identifier must be mapped, and all relationships must
be specified with their corresponding cardinality mappings inside the
entity element.
So you will need an entry in your orm.xml like the below, adding other attributes as required.
<entity-mappings>
<entity class="examples.Foo" metadata-complete="true">
<table name="NEW_FOO"/>
<attributes>
<id name="id"/>
</attributes>
</entity>
</entity-mappings>

JPA using variable Schema name in annotations

I'm using the Java Persistence API to describe tables from my database that i will manipulate in my code.
However, the schema used is not be the same depending on where my project will be installed. So, when I use the annotations, I would like that the SCHEMA field was a variable, but I can't make it:
#Entity
#Table(name = "TABLE_NAME", schema = schemaVariable, catalog = "")
How can I achieve that?
Is it possible with the persistence.xml file?

No, this is not possible. You can only use compile-time constants (which are all primitives and String) in annotations.
You can use final variables:
public class DatabaseMetadata {
public static final SCHEMA = "MySchema";
}
and then use it in annotation:
#Table(name = "TABLE_NAME", schema = DatabaseMetadata.SCHEMA, catalog = "")
but I think it's not what you wanted.
PS. On the other hand, there can be find examples of using i.e. Spring EL in annotations (see #Value annotation), but this requires custom annotation processor. AFAIK none of JPA providers gives you such ablility.

Putting schema information (like table, column, schema names) in java classes is a bad idea any time IMHO (forcing recompile if you want to deploy elsewhere). You could put that info in orm.xml and just deploy a different orm.xml dependent on your deployment requirement.
As for persistence.xml you would be dependent on your JPA provider having a persistence property that defined the default schema/catalog. I know DataNucleus JPA (what I use) has this, but no idea for Hibernate

If you know that you would be using different schemas, I'd suggest to use 2 mapping files and define
<entity-mappings>
<persistence-unit-metadata>
<persistence-unit-defaults>
<schema>HR</schema>
</persistence-unit-defaults>
</persistence-unit-metadata>
...
</entity-mappings>
In this way you will be able to easily change schemas, without any changes in the application code.