When using @ManyToOne in JPA, such as:

@ManyToOne(cascade = CascadeType.ALL)
private Project project;

JPA automatically generates a foreign key column, but this can cause naming issues and confusion. Here's why you should explicitly define the foreign key using @JoinColumn:

1. Default Naming Might Be Confusing

If you don’t specify @JoinColumn, JPA automatically creates a column based on the field name, usually in the format:

project_id (because the field is private Project project).

But depending on the naming strategy of your database (e.g., Hibernate defaults), the column name might be:

• project_id
• projectId
• fk_project (in some cases)

If you explicitly define the foreign key, you ensure consistency across different databases.

✅ Better: Explicit Foreign Key Name

@ManyToOne(cascade = CascadeType.ALL)
@JoinColumn(name = "project_id", nullable = false)
private Project project;

Now it's clear:

• The database column name must be project_id.
• nullable = false ensures that a DamageReport must always be linked to a Project.

2. Multiple Foreign Keys Can Cause Conflicts

Imagine another @ManyToOne in the same entity, like: