Lets tell I have two tables.
CREATE TABLE user (ID int AUTO_INCREMENT,PRIMARY KEY (ID));
CREATE TABLE points (ID int AUTO_INCREMENT, user_id int, points int,PRIMARY KEY (ID));
How can I use spring-boot jpa to request user and max points like this?
select u.ID,max(p.points) from user u, points p where u.id=p.user_id
Or any alternatives to solve this kind of problems?
Assuming you have a Repository of User:
public class User {
private int id;
private List<Point> points;
...
}
With a relationship to the Points object:
public class Point {
private int id;
private User User;
private int points;
...
}
I haven't tested, but you should be able to do:
User findFirstByIdOrderByPointPointsDesc(int userId)
Similar to example 18 in the docs.
The only problem you have, regardless of the query or Spring Data, is if you have two users with the same point values. If you need more logic around tie-breaking, it might be more worth it to write a #Query (with your query, plus the extra tie-breaking logic) or a #NativeQuery.
I usually create a class to hold result such as
public class Result {
private User user;
private int votes;
// getters and setters
}
And write a custom query in the repository to fetch the data
#Query(value = "SELECT new com.package.Result (u, MAX (p.points) )
FROM user u
JOIN points p
ON u.id = p.user_id
GROUP BY u")
List<Result> getPointsPerUser();
Replace com.package.Result with appropriate path to the Result class.
Below method can be written in Repo and used as Transaction as in dao layer, which will be accessible from service layer.
#Query(value = "SELECT max(transactionId) FROM TransactionPayloadInfo")
int getMaxTransactionId();
create a model of data.
public class Data {
private int id;
private int maxPoints;
// getters and setters method
}
And write your query like this for getting model of Data.
#Query(select packagename.Data(u.ID,max(p.points) ) from user u, points p where u.id=p.user_id)
Data findUserWithMaxVots();
Related
I have the following User entity:
public class User extends PanacheEntityBase{
#Id
#GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "DataIdGenerator")
#Column(name = "id")
public Long id;
public String name;
public String location;
public int age;
}
I also have the following endpoint: '/user', with a 'select' query parameter where you provide the column names you want to receive. It should be possible to select any combination of columns like: /user?select=id,name, /user?select=id,age, /user?select=name,age, /user?select=age,name
Based on the 'select' query I want to use a projection to get the selected columns only. Currently I'm using the query to create the following query fe: /user?select=id,name to SELECT d.id, d.name FROM User d, however I need the DTO to be dynamic based on the columns provided too.
Currently I have the following projection where UserDTO is a class with id and name attributes. This works fine, but if I change any parameter I need a different DTO.
// This variable is dynamically created based on query parameters
String query = 'SELECT d.id, d.name FROM User d'
return User.find(query).project(UserDTO.class).list();
Is it possible to make this projection DTO class more dynamic, so it supports all combinations?
I suspect the Panache API is not flexible enough at the moment to do what you are asking.
But you could use the Hibernate Reactive API without Panache:
#Inject
Mutiny.SessionFactory sf;
public Uni<List<Tuple>> find(String query) {
return sf.withSession(session ->
session.createQuery(query, Tuple.class).getResultList()
);
}
Once you have the Tuple, you can convert it to the type you prefer.
I have a database table which holds Metadata for documents. My task now is to get a list with documenttypes. The documenttypes are not unique in the database table but of course I want them to be in my list. The sql is very simple:
SELECT DISTINCT groupname, group_displayorder
FROM t_doc_metadata
ORDER BY group_displayorder;
I have learned that I can use projections to get a subset of fields from my entity DocMetadata. I solved this as follows. My Entity:
#Entity
#Table(name="T_DOC_METADATA")
#Data
public class DocMetadata {
..............
#Column(nullable=false)
private String displayname;
#Column(nullable=false)
private Integer displayorder;
#Column(nullable=false)
private String groupname;
#Column(name="GROUP_DISPLAYORDER",
nullable=false)
private Integer groupDisplayorder;
#Column(name="METADATA_CHANGED_TS",
nullable=false,
columnDefinition="char")
private String metadataChangedTimestamp;
..........
}
My inteface for projection:
public interface GroupnameAndOrder {
String getGroupname();
Integer getGroupDisplayorder();
void setGroupname(String name);
void setGroupDisplayorder(int order);
}
Now I thought I'd be extraordinary clever by adding these lines to my repository:
#Query("select distinct d.groupname, d.groupDisplayorder from DocMetadata d order by d.groupDisplayorder")
public List<GroupnameAndOrder> findSortedGroupnames();
Sadly, when iterating over the result list and calling getGroupname() the result is null.
So I changed the lines in my repository according to the documentation:
public List<GroupnameAndOrder> findBy();
Now I get the groupnames but of course they are not unique now. So it doesn't solve my problem.
Is there any way to receive a ordered list with unique groupnames?
You are trying to be too clever. Instead just write the proper find method and return the GroupnameAndOrder. Spring Data JPA will then only retrieve what is needed for the projection.
Something like this should do the trick.
List<GroupnameAndOrder> findDistinctByOrderByGroupDisplayorder();
I am implementing queries in my web application with JPA repositories. The two main tables I am querying from are FmReportTb and SpecimenTb.
Here are the two entity classes (only important attributes are listed).
//FmReportTb.java
#Entity
#Table(name="FM_REPORT_TB")
public class FmReportTb implements Serializable {
#Column(name="ROW_ID")
private long rowId;
#Column(name="FR_BLOCK_ID")
private String frBlockId;
#Column(name="FR_FULL_NAME")
private String frFullName;
#OneToOne
#JoinColumn(name="SPECIMEN_ID")
private SpecimenTb specimenTb;
FmReportTb has OneToOne relationship with SpecimenTb.
#Entity
#Table(name="SPECIMEN_TB")
public class SpecimenTb implements Serializable {
private String mrn;
#OneToOne(mappedBy="specimenTb", cascade=CascadeType.ALL)
private FmReportTb fmReportTb;
The query I am working on is to find all records in FmReportTb and show a few attributes from FmReportTb plus mrn from SpecimenTb.
Here is my JPA repository for FmReportTb:
#Repository
public interface FmReportRepository extends JpaRepository<FmReportTb, Long> {
#Query("select f from FmReportTb f where f.deleteTs is not null")
public List<FmReportTb> findAllFmReports();
Since, I am only showing part of the attributes from FmReportTb and one attribute from SpecimenTb, I decided to create a Value Object for FmReportTb. The constructor of the VO class assigns attributes from FmReportTb and grabs mrn attribute from SpecimenTb based on the OneToOne relationship. Another reason for using VO is because table FmReportTb has a lot of OneToMany children entities. For this particular query, I don't need any of them.
public class FmReportVO {
private String frBlockId;
private Date frCollectionDate;
private String frCopiedPhysician;
private String frDiagnosis;
private String frFacilityName;
private String frFullName;
private String frReportId;
private String filepath;
private String mrn;
public FmReportVO(FmReportTb fmReport) {
this.frBlockId = fmReport.getFrBlockId();
this.frCollectionDate = fmReport.getFrCollectionDate();
this.frCopiedPhysician = fmReport.getFrCopiedPhysician();
this.frDiagnosis = fmReport.getFrDiagnosis();
this.frFacilityName = fmReport.getFrFacilityName();
this.frFullName = fmReport.getFrFullName();
this.frReportId = fmReport.getFrReportId();
this.mrn = fmReport.getSpecimenTb().getMrn();
}
I implemented findall method in servicebean class to return a list of FmReportTb VOs.
//FmReportServiceBean.java
#Override
public List<FmReportVO> findAllFmReports() {
List<FmReportTb> reports = fmReportRepository.findAllFmReports();
if (reports == null) {
return null;
}
List<FmReportVO> fmReports = new ArrayList<FmReportVO>();
for (FmReportTb report : reports) {
FmReportVO reportVo = new FmReportVO(report);
String filepath = fileLoadRepository.findUriByFileLoadId(report.getFileLoadId().longValue());
reportVo.setFilepath(filepath);
fmReports.add(reportVo);
}
return fmReports;
}
Lastly, my controller looks like this:
#RequestMapping(
value = "/ristore/foundation/",
method = RequestMethod.GET,
produces = "application/json")
public ResponseEntity<List<FmReportVO>> getAllFmReports() {
List<FmReportVO> reports = ristoreService.findAllFmReports();
if (reports == null) {
return new ResponseEntity<List<FmReportVO>>(HttpStatus.NOT_FOUND);
}
return new ResponseEntity<List<FmReportVO>>(reports, HttpStatus.OK);
}
There are about 200 records in the database. Surprisingly, it took almost 2 full seconds to retrieve all the records in JSON. Even though I did not index all the tables, this is way too slow. Similar query takes about probably a few ms on the database directly. Is it because I am using Value Objects or JPA query tends to be this slow?
EDIT 1
This may have to do with the fact that FmReportTb has almost 20 OneToMany entities. Although the fetchmode of these child entities are set to LAZY, JPA Data repository tends to ignore the fetchmode. So I ended up using NamedEntityGraph to specify the attributes EAGER. This next section is added to the head of my FmReportTb entity class.
#Entity
#NamedEntityGraph(
name = "FmReportGraph",
attributeNodes = {
#NamedAttributeNode("fileLoadId"),
#NamedAttributeNode("frBlockId"),
#NamedAttributeNode("frCollectionDate"),
#NamedAttributeNode("frDiagnosis"),
#NamedAttributeNode("frFullName"),
#NamedAttributeNode("frReportId"),
#NamedAttributeNode("specimenTb")})
#Table(name="FM_REPORT_TB")
And then #EntityGraph("FmReportGraph") was added before the JPA repository query to find all records. After doing that, the performance is improved a little bit. Now fetching 1500 records only takes about 10 seconds. However, it still seems too slow given each json object is fairly small.
Answering for the benefit of others with slow JPA queries...
As #Ken Bekov hints in the comments, foreign keys can help a lot with JPA.
I had a couple of tables with a many to one relationship - a query of 100,000 records was taking hours to perform. Without any code changes I reduced this to seconds just by adding a foreign key.
In phpMyAdmin you do this by creating a Relationship from the "many" table to the "one" table. For a detailed explanation see this question: Setting up foreign keys in phpMyAdmin?
and the answer by #Devsi Odedra
I'm having spring data jpa repository.I the entity contain primary key id int and ipaddress string. The table contain only 1 record at a time otherwise null.
How do i retrieve the record using JPA , if it is not found return null.
#Repository
public interface IpConfigRepository extends JpaRepository<IpConfig, Integer> {
//
IpConfig findIpConfig();
}
According to the naming convention, you should define the method with the name findById(Integer id) ( assume the Id is the primary key )
Suppose you have a class A as shown below
class A{
private int id;
private String data;
// getters and setters
}
You can now search the items by the following ways.
public interface ARepo extends JpaRepository<A,Integer>{
// get all the records from table.
List<A> findAll();
// find record by id
A findById(int id);
// find record by data
A findByData(String data);
// find by date created or updated
A findByDateCreated(Date date);
// custom query method to select only one record from table
#Query("SELECT * FROM a limit 1;")
A findRecord();
}
I have two entities Person and Visit
Person has OneToMany relationship with Visit.
I was wondering if I want to save an new entry of Visit, and interm of using RestController. Is my approach correct? Or is there another way which is more efficient?
So I have the following controller which takes a VisitModel from the RequestBody, is it a correct way to call it like so?
VisitModel has the ID of person, and the needed properties for the Visit entity. I use the ID of person to look up in the personRepository for the related Person entry, whereafter I issue it to a new instance of Visit and then use the visitRepository to save it.
#RequestMapping(value="", method=RequestMethod.POST)
public String checkIn(#RequestBody VisitModel visit) {
Person person = personRepository.findById(visit.personId);
Visit newVisit = new Visit(visit.getCheckIn, person);
visitRepository.save(newVisit);
return "success";
}
The Visit entity looks as following
#Entity
public class Visit {
#Id
#GeneratedValue(strategy=GenerationType.AUTO)
private Long id;
#JsonProperty("check_in")
private Date checkIn;
#JsonProperty("check_out")
private Date checkOut;
#ManyToOne
#JoinColumn(name="personId")
private Person person;
public Visit(Date checkIn, Person person) {
this.checkIn = checkIn;
this.person = person;
}
public Date getCheckIn() {
return checkIn;
}
public void setCheckIn(Date checkIn) {
this.checkIn = checkIn;
}
public Date getCheckOut() {
return checkOut;
}
public void setCheckOut(Date checkOut) {
this.checkOut = checkOut;
}
public Person getPerson() {
return person;
}
}
I want to know of the following approach is correct. Or is there another way which is better?
You don't need to get a Person from the database to associate it with a Visit, of course. Because of, you need to have only id of a Person to save it in the foreign key column personId.
If you use JPA EntityManager
Person person = entityManager.getReference(Person.class, visit.personId);
for Hibernate Session
Person person = session.load(Person.class, visit.personId);
This methods just create a proxy and don't do any database requests.
With Hibernate Session I used new Person(personId) as #MadhusudanaReddySunnapu suggested. Everything worked fine.
What is the difference between EntityManager.find() and EntityManger.getReference()?
Hibernate: Difference between session.get and session.load
Yes, that seems to me to be the standard way to map a bidirectional relationship. EDIT: The personId column points to the "id" field of the Person entity.Eg:
#Id
private Long id;
UPDATE: 1: The VisitModel is a 'DTO' or Data Transfer Object. Any separate package is fine. You could consider putting them into a separate jar, so that anyone using your API (with java) can use the jar to create the data before making the call. 2) The way you save it is fine as far as I can see.