I am using Spring JPA to perform all database operations. However I don't know how to select specific columns from a table in Spring JPA?
For example:
SELECT projectId, projectName FROM projects
You can use projections from Spring Data JPA (doc). In your case, create interface:
interface ProjectIdAndName{
String getId();
String getName();
}
and add following method to your repository
List<ProjectIdAndName> findAll();
I don't like the syntax particularly (it looks a little bit hacky...) but this is the most elegant solution I was able to find (it uses a custom JPQL query in the JPA repository class):
#Query("select new com.foo.bar.entity.Document(d.docId, d.filename) from Document d where d.filterCol = ?1")
List<Document> findDocumentsForListing(String filterValue);
Then of course, you just have to provide a constructor for Document that accepts docId & filename as constructor args.
You can set nativeQuery = true in the #Query annotation from a Repository class like this:
public static final String FIND_PROJECTS = "SELECT projectId, projectName FROM projects";
#Query(value = FIND_PROJECTS, nativeQuery = true)
public List<Object[]> findProjects();
Note that you will have to do the mapping yourself though. It's probably easier to just use the regular mapped lookup like this unless you really only need those two values:
public List<Project> findAll()
It's probably worth looking at the Spring data docs as well.
In my situation, I only need the json result, and this works for me:
public interface SchoolRepository extends JpaRepository<School,Integer> {
#Query("select s.id, s.name from School s")
List<Object> getSchoolIdAndName();
}
in Controller:
#Autowired
private SchoolRepository schoolRepository;
#ResponseBody
#RequestMapping("getschoolidandname.do")
public List<Object> getSchool() {
List<Object> schools = schoolRepository.getSchoolIdAndName();
return schools;
}
With the newer Spring versions One can do as follows:
If not using native query this can done as below:
public interface ProjectMini {
String getProjectId();
String getProjectName();
}
public interface ProjectRepository extends JpaRepository<Project, String> {
#Query("SELECT p FROM Project p")
List<ProjectMini> findAllProjectsMini();
}
Using native query the same can be done as below:
public interface ProjectRepository extends JpaRepository<Project, String> {
#Query(value = "SELECT projectId, projectName FROM project", nativeQuery = true)
List<ProjectMini> findAllProjectsMini();
}
For detail check the docs
In my case i created a separate entity class without the fields that are not required (only with the fields that are required).
Map the entity to the same table.
Now when all the columns are required i use the old entity, when only some columns are required, i use the lite entity.
e.g.
#Entity
#Table(name = "user")
Class User{
#Column(name = "id", unique=true, nullable=false)
int id;
#Column(name = "name", nullable=false)
String name;
#Column(name = "address", nullable=false)
Address address;
}
You can create something like :
#Entity
#Table(name = "user")
Class UserLite{
#Column(name = "id", unique=true, nullable=false)
int id;
#Column(name = "name", nullable=false)
String name;
}
This works when you know the columns to fetch (and this is not going to change).
won't work if you need to dynamically decide the columns.
In my opinion this is great solution:
interface PersonRepository extends Repository<Person, UUID> {
<T> Collection<T> findByLastname(String lastname, Class<T> type);
}
and using it like so
void someMethod(PersonRepository people) {
Collection<Person> aggregates =
people.findByLastname("Matthews", Person.class);
Collection<NamesOnly> aggregates =
people.findByLastname("Matthews", NamesOnly.class);
}
I guess the easy way may be is using QueryDSL, that comes with the Spring-Data.
Using to your question the answer can be
JPAQuery query = new JPAQuery(entityManager);
List<Tuple> result = query.from(projects).list(project.projectId, project.projectName);
for (Tuple row : result) {
System.out.println("project ID " + row.get(project.projectId));
System.out.println("project Name " + row.get(project.projectName));
}}
The entity manager can be Autowired and you always will work with object and clases without use *QL language.
As you can see in the link the last choice seems, almost for me, more elegant, that is, using DTO for store the result. Apply to your example that will be:
JPAQuery query = new JPAQuery(entityManager);
QProject project = QProject.project;
List<ProjectDTO> dtos = query.from(project).list(new QProjectDTO(project.projectId, project.projectName));
Defining ProjectDTO as:
class ProjectDTO {
private long id;
private String name;
#QueryProjection
public ProjectDTO(long projectId, String projectName){
this.id = projectId;
this.name = projectName;
}
public String getProjectId(){ ... }
public String getProjectName(){....}
}
Using Spring Data JPA there is a provision to select specific columns from database
---- In DAOImpl ----
#Override
#Transactional
public List<Employee> getAllEmployee() throws Exception {
LOGGER.info("Inside getAllEmployee");
List<Employee> empList = empRepo.getNameAndCityOnly();
return empList;
}
---- In Repo ----
public interface EmployeeRepository extends CrudRepository<Employee,Integer> {
#Query("select e.name, e.city from Employee e" )
List<Employee> getNameAndCityOnly();
}
It worked 100% in my case.
Thanks.
You can use JPQL:
TypedQuery <Object[]> query = em.createQuery(
"SELECT p.projectId, p.projectName FROM projects AS p", Object[].class);
List<Object[]> results = query.getResultList();
or you can use native sql query.
Query query = em.createNativeQuery("sql statement");
List<Object[]> results = query.getResultList();
You can apply the below code in your repository interface class.
entityname means your database table name like projects.
And List means Project is Entity class in your Projects.
#Query(value="select p from #{#entityName} p where p.id=:projectId and p.projectName=:projectName")
List<Project> findAll(#Param("projectId") int projectId, #Param("projectName") String projectName);
It is possible to specify null as field value in native sql.
#Query(value = "select p.id, p.uid, p.title, null as documentation, p.ptype " +
" from projects p " +
"where p.uid = (:uid)" +
" and p.ptype = 'P'", nativeQuery = true)
Project findInfoByUid(#Param("uid") String uid);
You can use the answer suggested by #jombie, and:
place the interface in a separate file, outside the entity class;
use native query or not (the choice depended on your needs);
don't override findAll() method for this purpose but use name of your choice;
remember to return a List parametrized with your new interface (e.g. List<SmallProject>).
Using Native Query:
Query query = entityManager.createNativeQuery("SELECT projectId, projectName FROM projects");
List result = query.getResultList();
public static final String FIND_PROJECTS = "select ac_year_id,ac_year from tbl_au_academic_year where ac_year_id=?1";
#Query(value = FIND_PROJECTS, nativeQuery = true)
public List<Object[]> findByAcYearId(Integer ac_year_id);
this works for me
You can update your JPARepository as below.
#Query("select u.status from UserLogin u where u.userId = ?1 or u.email = ?1 or u.mobile = ?1")
public UserStatus findByUserIdOrEmailOrMobile(String loginId);
Where UserStatus is a Enum
public enum UserStatus
{
New,
Active,
Deactived,
Suspended,
Locked
}
Use:
#Query("SELECT e FROM #{#entityName} e where e.userId=:uid")
List<ClienteEnderecoEntity> findInfoByUid(#Param("uid") UUID uid);
{
"Comments":"Why not using JDBCTemplate",
"Url":"https://www.baeldung.com/spring-jdbc-jdbctemplate"
}
In our project we just get the ids from the study table. Do we need a SqlResultSetMapping or is it enough to just declare that we will get UUIDs from the query? When yes, how?
Mapping
#SqlResultSetMapping(name = "StudyMapping", classes = {
#ConstructorResult(targetClass = StudyId.class,
columns = {
#ColumnResult(name = "id", type = UUID.class)
}
)
})
Class for the mapping StudyId
#AllArgsConstructor
#Builder
#Getter
#Setter
public class StudyId {
private UUID id;
}
Query
SELECT DISTINCT id FROM Study;
I have Order entity which has a many-to-one relationship with Customer entity. I want to write a Spring Data JPA query to fetch all the orders that belong to the customer id.
Below is my Order entity
#Data
#NoArgsConstructor
#Builder
#AllArgsConstructor
#EqualsAndHashCode(exclude = "customer")
#ToString(exclude = "customer")
#Entity
#Table(name = "orders")
public class Order {
#Id
#GeneratedValue(strategy = GenerationType.AUTO)
private Long id;
private double price;
private LocalDate date;
#ManyToOne
#JoinColumn(name="customer_id", nullable = false)
#JsonBackReference
private Customer customer;
...
Spring Data JPA
#Repository
public interface OrderRepository extends JpaRepository<Order, Long> {
#Query("select orders from Order where orders.customer.id = ?#{principal.id}")
Page<Order> findAll(Pageable pageable);
}
Where am I going wrong? Also can we write the above query using fluent-style based on the method naming convention in Spring Data JPA.
This HQL query should work:
#Query("select o from Order o inner join o.customer c where c.id = ?#{principal.id}")
The query based on the method name doesn't seem to support join operations, or at least I couldn't find the keyword. You can check the documentation for the list of supported keywords.
This is my events entity.
#Data
#AllArgsConstructor
#NoArgsConstructor
#Entity
public class Events {
#Id
#GeneratedValue(strategy = GenerationType.AUTO)
private Long eventId;
#NotBlank(message = "Please Add Event name ")
#Length(max =100 ,min =2)
private String eventName ;
private String eventDescription;
// Each event is going to be mapped to a Location
#OneToOne(cascade = CascadeType.ALL)
#JoinColumn(
name = "location_id",
referencedColumnName = "locationId"
)
#NotNull
private Location location ;
#Temporal(TemporalType.DATE)
Date eventStartDate;
#Temporal(TemporalType.DATE)
Date eventEndDate;
#OneToOne(cascade = CascadeType.ALL)
#JoinColumn(
name = "category_id",
referencedColumnName = "categoryId"
)
#NotNull
private Categories categories;
}
In my controller ,i have access to locationId and categoryId as request params .
I am not getting how to define my eventsRepository to access by locationId and categoryId. What changes should i make to this repo for things to work .
#Repository
public interface EventsRepository extends JpaRepository<Events,Long> {
public Events findByCateoryAndLocation()
}
I think a few adjustments you need to get rid of the issue. The query builder uses actual column names, so if your column name is locationId, then use 'findByLocationId(Integer locationId)' as a prototype. And please make sure entity names suit table names.
#Repository
public interface EventRepository extends JpaRepository<Event, Integer>
{
Event findByLocationIdAndCategoryId(Integer locationId, Integer categoryId);
}
This is off-topic, but I would like to mention that please do not use Lombok in entity classes. Getter, setter, and construction generators are ok, but hascode and string generators would be dangerous if you use lazy initialization. You may not get benefits from lazy loadings.
You have 2 ways to get your jpa-query working:
Modify your JPA-Query:
#Repository
public interface EventsRepository extends JpaRepository<Events,Long>
{
public Events findByCateories_IdAndLocation_id(Long categoriesId, long locationId)
}
Use a custom query - annotate your jpa with #Query and use a native query
There is one additional point from my side.
Naming of your classes. You are using plural which conflicts with the business logic - especially to the DB-relations(see Events to Categories). I would use singular (Event, Category)
This is exactly what I did to solve this with the help of native query.
#Query(
value = "SELECT * FROM events where category_id = ?1 AND location_id = ?2",
nativeQuery = true
)
public List<Events> findByCategoryIdAndLocationIdIn(Long CategoryId , Long LocationId);
public interface UserRepository extends JpaRepository<User, Long> {
#Query(value = "SELECT * FROM USERS WHERE EMAIL_ADDRESS = ?0", nativeQuery = true)
User findByEmailAddress(String emailAddress);
}
Let's say I have the code above where I select * from user. What should I do if I don't want this method to return User object. Is there a way I can manually map the data to a custom object MyUser? Can I do all this in the UserRepository interface?
Thanks!
You can do something like this
#Query(value = "SELECT YOUR Column1, ColumnN FROM USERS WHERE EMAIL_ADDRESS = ?0", nativeQuery = true)
List<Object[]> findByEmailAddress(String emailAddress);
You have to do the mapping. Take a look at the Spring Data Repository as well. Source
What about interface based projection?
Basically you write interface with getters that correspond to SQL query parameters.
In this way you even don't need to force #Id parameter on projection:
#Entity
public class Book {
#Id
private Long id;
private String title;
private LocalDate published;
}
public interface BookReportItem {
int getYear();
int getMonth();
long getCount();
}
public interface BookRepository extends Repository<Book, Long> {
#Query(value = "select " +
" year(b.published) as year," +
" month(b.published) as month," +
" count(b) as count," +
" from Book b" +
" group by year(b.published), month(b.published)")
List<BookReportItem> getPerMonthReport();
}
It uses org.springframework.data.jpa.repository.query.AbstractJpaQuery$TupleConverter$TupleBackedMap underneath as proxy for interface in current Spring implementation.
It works for nativeQuery = true too.