Mapping two columns in JPA

Question

I have the following 3 tables

table: project
id
company_code
number
contract_type_code
account_type_code
other columns…

table: contract_type
id
company_code
code
name

table: account_type
id
company_code
code
name

The project table references contract_type and account_type tables through contract_type_code/company_code and account_type_code/company_code respectively.

The company_code and code columns are what make a contract_type and account_type unique.

I'm struggling with modelling and mapping this in JPA. I've tried with the @JoinColumn and @JoinColumns annotation and there's no way for me to make it work.

This is one of the ways I've been trying with no success:

public class Project implements Serializable {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    private Long companyCode;

    private Long number;

    @ManyToOne(fetch = FetchType.LAZY)
    @JoinColumns({
            @JoinColumn(name = "contract_type_code", referencedColumnName = "code"),
            @JoinColumn(name = "company_code", referencedColumnName = "company_code")
    })
    private ContractType contractType;

    @ManyToOne(fetch = FetchType.LAZY)
    @JoinColumns({
            @JoinColumn(name = "account_type_code", referencedColumnName = "code"),
            @JoinColumn(name = "company_code", referencedColumnName = "company_code")
    })
    private AccountType accountType;

This is the issue I'm getting with the mapping above:

Caused by: org.hibernate.MappingException: Unable to find column with logical name company_code in table contract_type

For this mapping:

@ManyToOne(fetch = FetchType.LAZY)
@JoinColumns({
        @JoinColumn(name = "contract_type_code", referencedColumnName = "code", insertable = false, updatable = false),
        @JoinColumn(name = "company_code", referencedColumnName = "company_code2", insertable = false, updatable = false)
})
private ContractType contractType;

I get:

Caused by: org.hibernate.DuplicateMappingException: Table [account] contains physical column name [company_code] referred to by multiple logical column names: [company_code], [companyCode]

Answer 1

I assume you have companyCode fields in the AccountType and ContractType. Annotate them as below (first error suggests JPA can't find them):

@Column(name = "company_code")

In your Project class modify companyCode field as follows (to avoid the second error):

@Column(name = "company")
private Long companyCode;

and keep mapping with:

insertable = false, updatable = false

Hope this will help. If not please add AccountType and ContractType classes to your question. Maybe then it will be easier to sort it out