I have 2 tables Customer and Contact

Customer Entity:
@OneToMany(cascade = CascadeType.REFRESH, mappedBy="customer", fetch = FetchType.EAGER)
@MapKey(name="fieldName")
private Map<String, Contact> contacts;

Contact Entity:
@ManyToOne(fetch = FetchType.LAZY)
@JoinColumn(name = "customer_ID")
private Customer customer;

@Column(name = "FIELD_NAME")
@NotNull
private String fieldName;

@Column(name = "FIELD_VALUE")
@Length(max = 100, message = "Maximum length allowed for user defined field is 100")
private String fieldValue;

The JPQL is,
select c from Customer c where c.contacts['home'].fieldValue='1234'
But I got the error message,
incorrect syntax near the keyword 'null'
I display the normal query as below (it's not copied, just write here roughly)

select ... from Customer as customer1, contact as contact1
where customer1.id=contact1.customer_id and
contact1.null = 'home' and
contact1.field_value='1234'
I find the mapkey is not translated to column name
contact1.null = 'home'.
It should be contact1.field_name = 'home'

Did I miss something here?
The database is MS SQL.

Since some problem for this MapKey, I am thinking to change the Map to Set.
Part of Customer Entity:
@OneToMany(cascade = CascadeType.REFRESH, mappedBy="customer", fetch = FetchType.EAGER)

private Set<Contact> contacts;

If use Set instead of Map, what's this JPQL should be?
select c from Customer c where c.contacts['home'].fieldValue='1234'