EJB entity relations onetomany

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Using @OneToMany and @ManyToOne entity relationship might sound little difficult and confusing in the beginning but actually it is very easy. I recently used it in one of my projects and it worked great.

Here is how the code in your entities should look like...

Assuming table 1 and table 2 have one to many relationship...then...

in the table 1 entity...you have...

...
    @OneToMany(mappedBy="table2mapping")
    private Collection table2list;
   ..associated getter and setter...

in the table2 entity..you have...

@JoinColumn(name = "table2ID", referencedColumnName = "table1ID", insertable=false, updatable=false)
    @ManyToOne
    private table1 table2mapping;

@JoinColumn should be changed depending upon your requirements...
Let me know if you have any questions...

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Multiple Persistence Units in JAVA EE project

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Hello All,

If you are trying to create multiple persistence units in your JAVA EE project...the below is how you do it...I recently had to do this for one of my projects and it worked great...

Persistence.xml should look like below

  
    provideryouareusing
    jdbc/db1
    entity.entity1
    entity.entity2
    true
    
    
  
  
    jdbc/db2
    entity.entity3
    true
    
  

In the entity manager bean class you have to clearly specify which PU is the entity using...something like shown below...

@PersistenceContext(unitName="PUname")

let me know if you have any questions...

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