These are the following classes:
#Entity
public class Question {
#Id
public Long id;
public String name;
#OneToMany(fetch = FetchType.LAZY, cascade = CascadeType.PERSIST)
#JoinColumn(name = "OWNER_ID", referencedColumnName = "QUES_ID")
public List<Choice> choices = new ArrayList<>();
}
#Named
#Singleton
public interface QuestionRepository extends CrudRepository<Question , Long> {
Question findByName(String name);
}
And in the Controller file I have this following File
#Transactional
public Result getQuestion() {
List<Choices> list = this.questionRepository.findByName("name").choices;
list.size();
return ok();
}
list.size() in getQuestion() throws me a LazyInitializationException because there is not open sessions
I know that changing the fetch type to EAGER or using a JPQL query above the function definition in QuestionRepository might solve it, but there are part in my application where those wont help and I would require to lazy fetch.
How would make the entire code in getQuestion() function use a single session/transaction or even better my entire request to take place in an single session/transaction?
From Spring Data JPA reference documentation
4.7.1. Transactional query methods
To allow your query methods to be transactional simply use #Transactional at the repository interface
you define.
Example 100. Using #Transactional at query methods
#Transactional(readOnly = true)
public interface UserRepository extends JpaRepository<User, Long> {
List<User> findByLastname(String lastname);
#Modifying
#Transactional
#Query("delete from User u where u.active = false")
void deleteInactiveUsers();
}
Typically you will want the readOnly flag set to true as most of the query methods will only read data. In contrast to that deleteInactiveUsers() makes use of the #Modifying annotation and overrides the transaction configuration. Thus the method will be executed with readOnly flag set to false.
So just add #Transactional annotation to your repository interfaces.
Related
My Film model explicitly states it should fetch its children Actors lazily.
#Entity
#Getter
#Setter
public class Film {
...
#ManyToMany(fetch = FetchType.LAZY)
#JoinTable(
name = "film_actor",
joinColumns = #JoinColumn(name = "film_id"),
inverseJoinColumns = #JoinColumn(name = "actor_id")
)
private List<Actor> cast = new ArrayList<>();
This actually works perfectly when using the service/repository in any other context:
#Override
public void run(String... args) throws Exception {
List<Film> films = filmService.getAllFilms();
System.out.println(films);
}
But then for some mysterious reason, ONLY when used in a Spring MVC controller method (using typical annotations like #Controller and #RequestMapping), it always comes back eagerly loaded...Why and how do I change this? If I have 1000 films I want to display at once, I don't want to load in a million actors!
#GetMapping("")
public String filmsPage(Model model){
List<Film> allMyFilms = filmService.getAllFilms();
model.addAttribute("films", allMyFilms);
return "film/film-list";
}
Incidentally, for completeness, here are my service/repository layers:
#Service
#RequiredArgsConstructor
public class FilmServiceImpl implements FilmService {
private final FilmRepository filmRepo;
...
#Override
public List<Film> getAllFilms() {
List<Film> films = filmRepo.findAll();
return films;
}
Repository layer:
#Repository
public interface FilmRepository extends JpaRepository<Film, Long> {
List<Film> findAll();
}
How do you verify that the association is eager? Spring MVC has something enabled by default which is called "open session in view", which allows lazy loading until the request is finished. If you "check" whether data is loaded through your debugger, the debugger will invoke the toString method of PersistentBag which will initialize the lazy collection.
I have a project with multiple implementation and an entity class Person.
In every implementation there is a different database, different table and different columns.
In the DAO layer and the business layer the code is the same.
How can I change only the persistence layer to have different implementation of Person entity class based on a profile and keep unchanged the rest of the code?
//I would like to change table and columns based on a profile
#Entity
#Table(name = "person")
public class Person {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
#Column(name = "id", unique = true, nullable = false)
private Integer id;
private String first_name;
private String last_name
//getters,setters
}
//I would like to keep DAO unchanged no matter the profile
public interface PersonDao {
public List<Person> listAll() throws Exception;
}
public class PersonDaoImpl implements PersonDao{
#Override
public List<Person> listAll() throws Exception{
CriteriaBuilder criteriaBuilder = entityManager.getCriteriaBuilder();
CriteriaQuery<Person> criteria = criteriaBuilder.createQuery(Person.class);
Root<Person> root = criteria.from(Person.class);
...the rest of the code
}
}
Have a generic abstract Person and PersonDao which will be extended/implemented by other classes (e.g. MongoPerson, MysqlPersonDao, PersonV2... based on your requirements). But use only Person and PersonDao in your service layer.
Autowire with Spring using qualifiers and configurations
I am having troubles testing whether a collection is loaded in Spring DataJpaTest.
For that I have created an entity that has id and list of items as seen below. The list should be lazy-loaded (so I am assuming it should not be loaded in the test).
#Data
#Entity
#Table(name = "examples")
public class Example {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
protected Long id;
#OneToMany(mappedBy = "example", cascade = CascadeType.ALL, fetch = FetchType.LAZY)
private List<ExampleElement> collection;
}
Repository code looks like this:
#Repository
public interface ExampleRepository extends PagingAndSortingRepository<Example, Long> {
#Query("SELECT e FROM Example e")
List<Example> findAllActive();
}
In the test I am creating a new Example entity, generating the collection, saving the entity to database and after that getting entities from database and checking whether the collections are initialized.
Test code looks like this:
#RunWith(SpringRunner.class)
#DataJpaTest
#AutoConfigureTestDatabase(replace = Replace.NONE)
public class ExampleRepositoryTest {
#Autowired
private ExampleRepository repository;
#Test
public void myTest() {
Example example = new Example();
example.setCollection(Utils.generateCollection()))
repository.save(example);
List<Example> actives = repository.findAllActive();
// tests in a loop whether the collection is initialized which should return false
}
I have tried the following:
Injecting TestEntityManager and getting the PersistenceUnitUtil from there using em.getEntityManager().getEntityManagerFactory().getPersistenceUnitUtil() and calling the isLoaded(actives.get(0).getCollection()) and isLoaded(actives.get(0), "collection") methods - both return true
Calling Hibernate.isInitialized(actives.get(0).getCollection()) and Hibernate.isPropertyInitialized(actives.get(0), "collection") methods, which both return true as well.
Checking what the collection contains - it is a PersistentBag containing the elements. I expect it to be null instead.
What am I missing?
I'm using Spring Boot (1.3.3.RELEASE) and Hibernate JPA in my project. My entity looks like this:
#Data
#NoArgsConstructor
#Entity
#Table(name = "rule")
public class RuleVO {
#Id
#GeneratedValue
private Long id;
#Column(name = "name", length = 128, nullable = false, unique = true)
private String name;
#Column(name = "tag", length = 256)
private String tag;
#OneToMany(mappedBy = "rule", cascade = CascadeType.ALL, orphanRemoval = true)
private List<RuleOutputArticleVO> outputArticles;
#OneToMany(mappedBy = "rule", cascade = CascadeType.ALL, orphanRemoval = true)
private List<RuleInputArticleVO> inputArticles;
}
My repository looks like this:
#Repository
public interface RuleRepository extends JpaRepository<RuleVO, Long> {
}
In some cases I need to fetch only id and name attributes of entity RuleVO. How can I achieve this? I found a notice it should be doable using Criteria API and Projections but how? Many thanks in advance. Vojtech
UPDATE:
As has been pointed out to me, I'm lazy and this can very well be done hence I'm updating my answer after having looked around the web for a proper one.
Here's an example of how to get only the id's and only the names:
#Repository
public interface RuleRepository extends JpaRepository<RuleVO, Long> {
#Query("SELECT r.id FROM RuleVo r where r.name = :name")
List<Long> findIdByName(#Param("name") String name);
#Query("SELECT r.name FROM RuleVo r where r.id = :id")
String findNameById(#Param("id") Long id);
}
Hopefully this update proves helpful
Old Answer:
Only retrieving the specific attributes name/id is not possible as this is not how spring was designed or any SQL database for that matter as you always select a row which is an entity.
What you CAN do is query over the variables in the entity, for instance:
#Repository
public interface RuleRepository extends JpaRepository<RuleVO, Long> {
public RuleVo findOneByName(String name);
public RuleVo findOneByNameOrId(String name, Long id);
public List<RuleVo> findAllByName(String name);
// etc, depending on what you want
}
You can modify these however you want w.r.t. your needs. You can call these methods directly via the autowired repository
See http://docs.spring.io/spring-data/jpa/docs/current/reference/html/ Section 5.3 for more options and examples
interface IdOnly{
String getId();
}
#Repository
public interface RuleRepository extends JpaRepository<RuleVO, Long> {
public List<IdOnly> findAllByName(String name);
}
I notice that this is a very old post, but if someone is still looking for an answer, try this. It worked for me.
You can also define custom constructor to fetch specific columns using JPQL.
Example:
Replace {javaPackagePath} with complete java package path of the class
use as a constructor in JPQL.
public class RuleVO {
public RuleVO(Long id, String name) {
this.id = id;
this.name = name;
}
}
#Repository
public interface RuleRepository extends JpaRepository<RuleVO, Long> {
#Query("SELECT new {javaPackagePath}.RuleVO(r.id, r.name) FROM RuleVo r where r.name = :name")
List<RuleVO> findIdByName(#Param("name") String name);
}
Yes, you can achieve it with projections. You have many ways to apply them:
If you could upgrade to Spring Data Hopper, it provides an easy to use support for projections. See how to use them in the reference documentation.
Otherwise, first of all create a DTO with the attributes you want to load, something like:
package org.example;
public class RuleProjection {
private final Long id;
private final String name;
public RuleProjection(Long id, String name) {
this.id = id;
this.name = name;
}
public Long getId() {
return id;
}
public String getName() {
return name;
}
}
Of course, you could use Lombok annotations also.
Then, you can use in the JPQL queries like this:
select new org.example.RuleProjection(rule.id, rule.name) from RuleVO rule order by rule.name
Another option, if you want to avoid using DTO class names in your queries, is to implement your own query method using QueryDSL. With Spring Data JPA, you have to:
Create a new interface with the new method. Ex:
public interface RuleRepositoryCustom {
public List<RuleProjection> findAllWithProjection();
}
Change your repository to extend the new interface. Ex:
public interface RuleRepository extends JpaRepository<RuleVO, Long>, RuleRepositoryCustom {
...
Create an implementation of the Custom repository using the Spring Data JPA QueryDSL support. You have to previously generate the Q clases of QueryDSL, using its Maven plugin. Ex:
public class RuleRepositoryImpl {
public List<RuleProjection> findAllWithProjection() {
QRuleVO rule = QRuleVO.ruleVO;
JPQLQuery query = getQueryFrom(rule);
query.orderBy(rule.name.asc());
return query.list(ConstructorExpression.create(RuleProjection.class, rule.id, rule.name));
}
}
You can do it by using #Query annotation(HQL).
Please refer to the Spring docs below:
http://docs.spring.io/spring-data/jpa/docs/current/reference/html/#jpa.query-methods.at-query
(search for #Query in spring document)
Does anyone have any idea how to get a single column using Spring Data JPA? I created a repository like below in my Spring Boot project, but always get the {"cause":null,"message":"PersistentEntity must not be null!"} error when accessing the Restful URL.
#RepositoryRestResource(collectionResourceRel = "users", path = "users")
public interface UsersRepository extends CrudRepository<Users, Integer> {
#Query("SELECT u.userName FROM Users u")
public List<String> getUserName();
}
Then if I access the Restful URL like ../users/search/getUserName, I get the error:
{"cause":null,"message":"PersistentEntity must not be null!"}
Create a Projection interface
public interface UserNameOnly {
String getUserName();
}
Then in your repository interface return that type instead of the user type
public interface UserRepository<User> extends JpaRepository<User,String> {
List<UsernameOnly> findNamesByUserNameNotNull();
}
The get method in the projection interface must match a get method of the defined type on the JPA repository, in this case User.
The "findBySomePropertyOnTheObjectThatIsNotNull" allows you to get a List of the entities (as opposed to an Iterable) based on some criteria, which for a findAll can simply be if the unique identifier (or any other NonNull field) is not null.
Concept is : In your entity class create a constructor with only required instant variables. And use that constructor in the repository method shown below.
Lets say you have a interface Repository like below
Repository implementation:
public interface UserRepository<User> extends JpaRepository<User,String>
{
#Query(value = "select new com.org.User(usr.userId) from User usr where usr.name(:name)")
List<User> findUserIdAlone(#Param("name") String user);
}
In Controller
#RestController
public class UserController
{
#Autowired
private UserRepository<User> userRepository;
#Res
public ResponseEntity<User> getUser(#PathVariable("usrname") String userName)
{
User resultUser = usrRepository.findUserIdAlone(userName);
return ResponseEntity.ok(resultUser);
}
}
public class User
{
private String userId,userName;
public User(String userId)
{
this.userId=userId;
}
// setter and getters goes here
}
This Works for me.
public interface UserDataRepository extends JpaRepository<UserData, Long> {
#Query(value = "SELECT emp_name FROM user_data", nativeQuery = true)
public List<Object[]> findEmp_name();
}
System.out.println("data"+ userDataRepository.findEmp_name());
The above line gave me this result :
data[abhijeet, abhijeet1, abhijeet2, abhijeet3, abhijeet4, abhijeet5]
If you want to only return a single column you should look at Projections and Excerpts which will allow you to filter specific columns and other things that are usefule.
If you need list all of the users, try select userName from Users, if you need one user use "where" look at spring data JPA http://docs.spring.io/spring-data/jpa/docs/current/reference/html/ , try change CrudRepository to JpaRepository
It is possible to provide custom implementations of methods in a Spring Data JPA repository, which enables complete control on queries and return types. The approach is as follows:
Define an interface with the desired method signatures.
Implement the interface to achieve the desired behavior.
Have the Repository extend both JpaRepository and the custom interface.
Here is a working example that uses JpaRepository, assuming a user_table with two columns, user_id and user_name.
UserEntity class in model package:
#Entity
#Table(name = "user_table")
public class UserEntity {
#Id
#GeneratedValue(strategy=GenerationType.AUTO)
#Column(name = "user_id")
private Long userId;
#Column(name = "user_name")
private String userName;
protected UserEntity() {}
public UserEntity(String userName) {
this.userName = userName;
// standard getters and setters
}
Define interface for the custom repository in the repository package:
public interface UserCustomRepository {
List<String> findUserNames();
}
Provide implementation class for the custom interface in the repository package:
public class UserCustomRepositoryImpl implements UserCustomRepository {
// Spring auto configures a DataSource and JdbcTemplate
// based on the application.properties file. We can use
// autowiring to get a reference to it.
JdbcTemplate jdbcTemplate;
#Autowired
public void setJdbcTemplate(JdbcTemplate jdbcTemplate) {
this.jdbcTemplate = jdbcTemplate;
}
// Now our custom implementation can use the JdbcTemplate
// to perform JPQL queries and return basic datatypes.
#Override
public List<String> findUserNames() throws DataAccessException {
String sql = "SELECT user_name FROM user_table";
return jdbcTemplate.queryForList(sql, String.class);
}
}
Finally, we just need to have the UserRepository extend both JpaRepository and the custom interface we just implemented.
public interface UserRepository extends JpaRepository<UserEntity, Long>, UserCustomRepository {}
Simple test class with junit 5 (assuming the database is initially empty):
#SpringBootTest
class UserRepositoryTest {
private static final String JANE = "Jane";
private static final String JOE = "Joe";
#Autowired
UserRepository repo;
#Test
void shouldFindUserNames() {
UserEntity jane = new UserEntity(JANE);
UserEntity joe = new UserEntity(JOE);
repo.saveAndFlush(jane);
repo.saveAndFlush(joe);
List<UserEntity> users = repo.findAll();
assertEquals(2, users.size());
List<String> names = repo.findUserNames();
assertEquals(2, names.size());
assertTrue(names.contains(JANE));
assertTrue(names.contains(JOE));
}
}