JPA OneToOne annotation

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The @OneToOne annotation is used to implement One-to-One relationship. Two entities are said to be in One-to-One relationship if one entity has only one occurrence in other entity.

Example:

    // On Customer class:
    @OneToOne(optional=false)
    @JoinColumn(
        name="CUSTREC_ID", unique=true, nullable=false, updatable=false)
    public CustomerRecord getCustomerRecord() { return customerRecord; }
 
    // On CustomerRecord class:
    @OneToOne(optional=false, mappedBy="customerRecord")
    public Customer getCustomer() { return customer; }