Save child objects automatically using JPA Hibernate

Question

I have a one-to-many relation between Parent and Child table   In the parent object I have a   List lt Child gt  setChildren List lt Child gt  childs    I also have a foreign key in the Child table  This foreign key is an ID that references a Parent row in database   So in my database configuration this foreign key can not be NULL  Also this foreign key is the primary key in the Parent table   So my question is how I can automatically save the children objects by doing something like this   session save parent     I tried the above but I m getting a database error complaining that the foreign key field  in the Child table can not be NULL  Is there a way to tell JPA to automatically set this foreign key into the Child object so it can automatically save children objects   Thanks in advance

User · Accepted Answer

I tried the above but I m getting a database error complaining that the foreign key field in the Child table can not be NULL  Is there a way to tell JPA to automatically set this foreign key into the Child object so it can automatically save children objects    Well  there are two things here    First  you need to cascade the save operation  but my understanding is that you are doing this or you wouldn t get a FK constraint violation during inserts in the  child  table    Second  you probably have a bidirectional association and I think that you re not setting  both sides of the link  correctly  You are supposed to do something like this   Parent parent   new Parent        Child c1   new Child        c1 setParent parent    List lt Child gt  children   new ArrayList lt Child gt     children add c1   parent setChildren children    session save parent     A common pattern is to use link management methods    Entity public class Parent        Id private Long id        OneToMany mappedBy  parent       private List lt Child gt  children   new ArrayList lt Child gt                   protected void setChildren List lt Child gt  children            this children   children             public void addToChildren Child child            child setParent this           this children add child             And the code becomes   Parent parent   new Parent        Child c1   new Child         parent addToChildren c1    session save parent     References   Hibernate Core Reference Guide   1 2 6  Working bi-directional links

User · Answer

in your setChilds  you might want to try looping thru the list and doing something like  child parent   this    you also should set up the cascade on the parent to the appropriate values

User · Answer

In short set cascade type to all   will do a job  For an example in your model  Add Code like this     OneToMany mappedBy    receipt   cascade CascadeType ALL   private List saleSet

User · Answer

Following program describe how bidirectional relation work in hibernate   When parent will save its list of child object will be auto save   On Parent side        Entity      Table name  clients       public class Clients implements Serializable               Id           GeneratedValue strategy   GenerationType IDENTITY                 OneToMany mappedBy  clients   cascade CascadeType ALL            List lt SmsNumbers gt  smsNumbers          And put the following annotation on the child side      Entity    Table name  smsnumbers     public class SmsNumbers implements Serializable          Id       GeneratedValue strategy   GenerationType IDENTITY       int id       String number       String status       Date reg date        ManyToOne       JoinColumn name    client id        private Clients clients          and getter setter        Main class    public static void main String arr           Session session   HibernateUtil openSession            getting transaction object from session object     session beginTransaction         Clients cl new Clients  Murali    1010101010        SmsNumbers sms1 new SmsNumbers  99999    Active   cl       SmsNumbers sms2 new SmsNumbers  88888    InActive   cl       SmsNumbers sms3 new SmsNumbers  77777    Active   cl       List lt SmsNumbers gt  lstSmsNumbers new ArrayList lt SmsNumbers gt         lstSmsNumbers add sms1       lstSmsNumbers add sms2       lstSmsNumbers add sms3       cl setSmsNumbers lstSmsNumbers       session saveOrUpdate cl       session getTransaction   commit         session close

User · Answer

Here are the ways to assign parent object in child object of Bi-directional relations    Suppose you have a relation say One-To-Many then for each parent object a set of child object exists  In bi-directional relations each child object will have reference to its parent   eg   Each Department will have list of Employees and each Employee is part of some department This is called Bi directional relations    To achieve this  one way is to assign parent in child object while persisting parent object  Parent parent   new Parent        Child c1   new Child        c1 setParent parent    List lt Child gt  children   new ArrayList lt Child gt     children add c1   parent setChilds children    session save parent     Other way is  you can do using hibernate Intercepter this way helps you not to write above code for all models   Hibernate interceptor provide apis to do your own work before perform any DB operation Likewise onSave of object  we can assign parent object in child objects using reflection   public class CustomEntityInterceptor extends EmptyInterceptor         Override     public boolean onSave              final Object entity  final Serializable id  final Object   state  final String   propertyNames              final Type   types            if  types    null                for  int i   0  i  lt  types length  i                      if  types i  isCollectionType                          String propertyName   propertyNames i                       propertyName   propertyName substring 0  1  toUpperCase     propertyName substring 1                       try                           Method method   entity getClass   getMethod  get    propertyName                           List lt Object gt  objectList    List lt Object gt   method invoke entity                            if  objectList    null                                for  Object object   objectList                                    String entityName   entity getClass   getSimpleName                                    Method eachMethod   object getClass   getMethod  set    entityName  entity getClass                                     eachMethod invoke object  entity                                                                                  catch  NoSuchMethodException   InvocationTargetException   IllegalAccessException e                            throw new RuntimeException e                                                                           return true             And you can register Intercepter to configuration as  new Configuration   setInterceptor  new CustomEntityInterceptor

User · Answer

I believe you need to set the cascade option in your mapping via xml annotation  Refer to Hibernate reference example here   In case you are using annotation  you need to do something like this    OneToMany cascade   CascadeType PERSIST     Other options are CascadeType ALL  CascadeType UPDATE etc

User · Answer

Use org hibernate annotations for doing Cascade   if the hibernate and JPA are used together   its somehow complaining on saving the child objects

[java] Save child objects automatically using JPA Hibernate

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