I have two entity classes Request,User:
//Ommiting some annotations for brevity
public class User{
private Long id;
private String name;
private Integer age;
}
public class Request{
private Long id;
private String message;
private Date createTime;
#ManyToOne
#JoinColumn(name="user_id")
private User user;
}
I can sort request list by create time :
Sort = new Sort(Direction.ASC,"createTime");
Is there a possible way to sort request list by User's name? Like:
Sort = new Sort(Direction.ASC,"User.name");
Yes. new Sort(Direction.ASC,"user.name"); should work just fine.
Spring Data JPA will left outer join the User to the Request and order by the joined column's name resulting in SQL like this:
select
id, message, createTime
from
Request r
left outer join User u on u.id = r.user_id
order by
u.name asc
This works great on one-to-one and, like you have here, many-to-one relationships but because a left outer join is employed to implement the order by clause, if the joined entity represents a many relationship (like in a one-to-many), the Sort may result in SQL in which duplicate records are returned. This is the case because the Sort parameter will always result in a new left outer join even if the entity being joined is already joined in the query!
Edit Incidentally, there is an open ticket concerning this issue: https://jira.spring.io/browse/DATAJPA-776
Related
I have a table in the database that has a #OneToMany link to another table, JPA in standard form will return me the values from the other table as a list, however I would like to get the records as :
SELECT * FROM a LEFT JOIN b ON b.a_id = a.id
so if there are 2 records in the table "b" then I should get a list of 2 elements, not a one element list with a list inside that has values from table "b". Additionally, I will point out that I care to implement this by the function "Page findAll(#Nullable Specification spec, Pageable pageable);".
Example entity:
#Entity
public class A {
private Long id;
#OneToMany
private List<B> b;
soo i like to look like this
#Entity
public class A {
private Long id;
#OneToOne
private B b;
But when theres more that one B i will get second rekord instede of error.
What can I do to achieve this?
I have two entities(Invoice and InvoiceItems) without adding any relationship.
Invoice
public class Invoice {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
private Long invoiceID;
#Column(name="code")
private String code;
//other columns
}
Invoice Items
public class InvoiceItems {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
private Long invItemID;
#Column(name="invoice_id")
private Integer invoiceId;
//other columns
}
Can I join these entities and get data without adding relationship using JPA?
If it isn't possible how to join 2 entities using JPQL or Native query?
If your data is valid then using native query you can do that
#Query(nativeQuery = true, "select * from Invoice i join InvoiceItems im on i.id = im.invoice_id")
public List<Invoice> findData();
But that is not a good way join without relation using JPA.
Yes, you can join these entities and get data without adding relationship using JPA, but it's a little bit losing the purpose of using JPA.
You need to create a java class first, which will be the returning data object from the DB. After that you can use entityManager's createNamedQuery method to get the result.
createNamedQuery(String sqlString, ResultClass.Class)
sqlString may be something like:
SELECT INV.INVOICE_ID
INV.CODE
INV_ITEMS.INV_ITEM_ID
FROM INVOICE INV
JOIN INVOICE_ITEMS INV_ITEMS
ON INV.INVOICE_ID = INV_ITEMS.INVOICE_ID;
And the corresponding ResultClass:
public class ResultClass {
private Long invoiceID;
private String code;
private Long invItemID;
// other columns
}
Or you can even use RowMapper to map the object all by yourself for more flexibility by using JdbcTemplate with query() method.
i have the following constellation:
public final class ApplicationUser {
private final #Id
#Wither
long applicationUserId;
#NotNull
#Size(min = 4, max = 20)
private final
String login;
#NotNull
#Email
private final
String eMail;
#Wither
private Set<Privilege> privileges;
}
Now i want to query one ApplicationUser by its login which is done by a simple sql Query.
My question now:
Is there any spring-data-jdbc related thing to jpa´s join fetch so that i can fetch the associated Set<Privilege> privileges in one declared query?
Or do i have to fire another query like so:
query ApplicationUser by its login
query Privilege by its foreign key applicationuser
Thank you
Your answer describes the default way to do this. If you want to avoid the extra select you could use a statement that contains the join and use a ResultSetExtractor to construct your entities.
Pro: More efficient at runtime.
Con: More work for you.
I should have waited with my question, because i´ve just found an answer myself.
So here is my answer:
Just type this sql query onto your repository function:
#Query("select a.applicationuserid, a.email, a.login, p from applicationuser a left outer join privilege p on a.applicationuserid = p.applicationuser where lower(a.login) = lower(:login)")
In the corresponding logs there has been fired a second sql query to fetch the privilegs.
I'm new to hql, I referred to a site to write hql query in Spring Framework, but it throws "Path expected for join!" exception
My query is
"from GaugeCateSelect cs inner join PreferredUrl purl on cs.survey=purl.survey where purl.uuid=:uuid"
I want to connect both table with "survey".
How can I sort it out?
Update
Two tables, names are GaugeCateSelect and PreferredUrl. The "survey" field is common for both table. uuid is in PreferredUrl. I want to get all data from GaugeCateSelect when I pass the uuid to PreferredUrl table. (In short, Pass uuid to PreferredUrl, then find the survey number from PreferredUrl and check the number with GaugeCateSelect table, if exists get all data)
Update 2
There is no primary/foreign key reference relationship between two tables. but common field survey is there
GaugeCateSelect class
class GaugeCateSelect {
private int id;
private String categoryName;
private int posNeg;
private Survey survey; //survey is in foreign key relationship of survey table
//Annotation, getters and setters were removed for easiness.
}
PreferredUrl class
public class PreferredUrl {
private int preferredUrlId;
private String uuid;
private int enabled;
private Survey survey; //survey is in foreign key relationship of survey table
//Annotation, getters and setters were removed for easiness.
}
Maybe you should check the Hibernate version you use as there is a difference when joining unrelated entities as discussed here: https://www.thoughts-on-java.org/how-to-join-unrelated-entities/
My question is about the way Spring data is generating the query .
I have two entities : Message , Sender
#Entity
public class Message extends BaseEntity {
#ManyToOne
protected Account sender;
}
I have a call to
messageDao.findBySenderId(Long id)
The result is query all columns from the two two table with a left outer join between the two tables , but my expectation was simply to just select from message table where sender_id = the passed value.
So is there a way to force selecting only the first message entity and not to join with the other one? I want simple condition in the where clause
by using findBy not custom #Query
You will need a repository like (untested) :
#Repository
public interface MessageRepository extends JpaRepository<Message, Long> {
Message findFirstBySenderId(Long id);
}
See repositories.query-methods
I think Hibernate is doing a LEFT JOIN because your #ManyToOne is optional = true (default).
Try:
#ManyTone(optional = false)
And you will see Hibernate doing a query without a JOIN, as you expected.
You can use fetch type LAZY for the associations types:
#ManyToOne(optional = false, fetch = FetchType.LAZY)