E-mail from Ian Evans:

For example, I generated several entities from a database schema, and was
cleaning up the entity field names by using the refactoring engine. For a
many-to-many relationship of customers and accounts, the Customer entity
misnamed the accounts field (it used accountId, from the column in the
database), and Account had a similar problem with customerId for customers. I
renamed these fields to accounts and customers, respectively, but the
relationship annotations weren't updated:

In Customer.java:
    @ManyToMany(mappedBy = "customerId")
    private Collection<Account> accounts;

In Account.java:
    @JoinTable(name = "BANK_CUSTOMER_ACCOUNT_XREF")
    @ManyToMany
    private Collection<Customer> customers;

The refactoring engine needs to update annotation elements. In my case, it
should have updated the entities to the following.

In Customer.java:
    @ManyToMany(mappedBy = "customers")
    private Collection<Account> accounts;

In Account.java:
    @JoinTable(name = "BANK_CUSTOMER_ACCOUNT_XREF")
    @ManyToMany
    private Collection<Customer> customers;