This week's book giveaway is in the Java 9 forum.
We're giving away four copies of Java 9 Modularity: Patterns and Practices for Developing Maintainable Applications and have Sander Mak & Paul Bakker on-line!
See this thread for details.
Win a copy of Java 9 Modularity: Patterns and Practices for Developing Maintainable Applications this week in the Java 9 forum!
  • Post Reply Bookmark Topic Watch Topic
  • New Topic

JPA Persistance with mapping  RSS feed

 
shashank dwivedi
Ranch Hand
Posts: 67
AngularJS Java MySQL Database
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
I am new to JPA and need some help understanding persisting JPA parent entity along with it's child (through Mapping).
Say I have following two entities



Now I am trying to save Employee setting Address Entity to it.But it throws a foreign key validation exception because e_id is auto_increment and is generated by database while save.
Does JPA provide some mechanism to handle this ?

 
E Armitage
Rancher
Posts: 989
9
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
you should not be defining the emp_id property in the address entity. With JPA you are supposed to defining the relationships using objects not manually defining the database key links.
 
Rafael de Sousa
Greenhorn
Posts: 12
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
Since your Employee entity doesn't have a compound primary key, you don't need to set all those parameters on Address just to target your employee. Try something like this:



Some highlights you should consider when refactoring your code:

* insertable and updatable , when setted to false, are meant to inform the persistence provider that whenever an insert and/or update operation are fired on Address entity it should not include the mapping on the generated query.
* referencedColumnName is used to specify a column name which the foreign key targets. When not present, the default behavior is target's primary key.

Just remember, the Entity who holds the "mappedBy" is the target(Address), the other one the source Entity(Employee).
 
It is sorta covered in the JavaRanch Style Guide.
  • Post Reply Bookmark Topic Watch Topic
  • New Topic
Boost this thread!