在 SQL 或 JPQL 中查询以获取单向关系一对多

Question

I'm building an API for the company where I work and it is my first time using Spring Boot, so I'm having some doubts. So I have a One-To-Many unidirectional relationship, from my parent class (Compania) to my child class (Office). The thing is that I don't know how to query for the Office objects that are part of the Compania object. I think it should be a straightforward solution, but I can't manage to find it.

Hibernate creates for me an extra table that is called COMPANIA_OFFICE and I don't know how to use it with a SQL or JPQL query. So right now in my database, I have a table called COMPANIA, another one called OFFICE, and the last one called COMPANIA_OFFICE (this one contains COMPANIA_ID and OFFICE_ID, as I don't have the FK in either of the 2 classes it uses an auxiliary table to join them, I suppose).

What I want to achieve is in a GET request like this one:

GET /companias/{companiaId}/office/{officeName} --> Return a list with the offices that have that name from a specified company by id .

The classes that I have now are these:

Compania

@Entity(name = "Compania")
    @Table(
        name = "compania"
    )
    public class Compania {
        @Id
        @SequenceGenerator(
            name = "compania_sequence",
            sequenceName = "compania_sequence",
            allocationSize = 1
        )
        @GeneratedValue(
            strategy = GenerationType.SEQUENCE,
            generator = "compania_sequence"
        )
        @Column(
            nullable = false
        )
        private Long id;
    
        @Column(
            name = "name",
            nullable = false,
            unique = true
        )
        private String name;
    
        @OneToMany(
            mappedBy = "compania",
            cascade = CascadeType.ALL,
            fetch = FetchType.LAZY,
            orphanRemoval = true
        )
        private List<Office> office;

    ...Constructors...
    ... Getters and Setters...

Office (Child)

@Entity()
@Table()
public class Office {
    @Id
    @SequenceGenerator(
        name = "office_sequence",
        sequenceName = "office_sequence",
        allocationSize = 1
    )
    @GeneratedValue(
        strategy = GenerationType.SEQUENCE,
        generator = "office_sequence"
    )
    @Column(
        nullable = false
    )
    @JsonIgnore
    private Long id;

    @Column(
        name = "idRef",
        nullable = false
    )
    private int idRef;

    @Column(
        name = "title",
        nullable = false
    )
    private String title;

    @Column(
        name = "name"
    )
    private String name;

    ...Constructors...
    ... Getters and Setters...

So my problem is that I don't know how to make that query in spring Boot. I don't if using straight SQL or JPQL.

Thanks in advance!

Edit. I've tried using a native Query like this:

@Query(
        value = "select o.* from office o " +
            "inner join compania_office co on o.id = co.office_id " +
            "inner join compania c on c.id = co.compania_id " +
            "where c.id = :companiaId and lower(o.title) like lower(:officeTitle) " +
            "order by o.id_ref asc;",
        nativeQuery = true
    )
    List<Office> findOfficesByTitleLike(@Param("companiaId")Long companiaId,@Param("officeTitle") String officeTitle);

It works when I'm using a Database manager like Navicat or the one embedded in IntelliJ doing a common query. But when I try to use it with my API it gives me this error:

org.springframework.dao.InvalidDataAccessResourceUsageException: could not extract ResultSet; SQL [n/a]; nested exception is org.hibernate.exception.SQLGrammarException: could not extract ResultSet

Do you know what could be happening? Thanks!

Answer 1

Recently I had a similar issue. I managed it to fetch data from two Entities/tables by using JDBC template. However, first I created a class where are included only the columns that I require. The following is my solution and the suggestion for your issue:

    @GetMapping("/testi2")
public List<CustomerResponse> getCCP2() {
    String sql = "SELECT top 20 c.ID, c.CustomerNumber, c.Name, c.Surname, c.Area, c.City, c.Address, c.PhoneNumber, c.CustomerTypeID, c.Enabled, c.DateCreated, p.Id, p.Debit, p.Credit\n" +
            "FROM TblCustomer c OUTER APPLY\n" +
            "     (SELECT TOP 1 p.*\n" +
            "      FROM TblPayments p\n" +
            "      WHERE c.CustomerNumber = p.CustomerNumber\n" +
            "      ORDER BY p.id DESC \n" +
            "     ) p;";
    List<CustomerResponse> result = jdbcTemplate.query(
            sql,
            new BeanPropertyRowMapper(CustomerResponse.class));

    return result;
}

where class <CustomerResponse> is holding "ID, CustomerNumber, Name, Surname, Area, City, Address, PhoneNumber, CustomerTypeID, Enabled, c.DateCreated, Id, Debit, Credit".

Answer 2

I don't know if that's your problem, but I had a similar issue recently and the string param, :officeTitle in your case, it wasn't being passed as ':officeTitle' (SQL varchar) to sql, so I have solved it casting the param to varchar(255).

...  like lower(cast(:officeTitle AS varchar(255)))

I think nativeQuery doesn't cast the parameter automatically