I am trying to execute group by query with Spring Data JPA and Query DSL.
But, I am getting following exception:-
org.springframework.beans.factory.UnsatisfiedDependencyException:
Error creating bean with name 'japanWHTDaoImpl':
Unsatisfied dependency expressed through field 'wht21940000DataRepo';
nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'japanWHT21940000DataRepository':
Invocation of init method failed; nested exception is java.util.NoSuchElementException
I tried to write custom repository implementation and giving below my interfaces and impl classes:
Custom interface:
public interface JapanWHT21940000DataRepositoryCustom {
List<WHT21940000Royalties> findLocalCcyAmtsByRemarks();
}
Custom Impl class:
#Repository
#Transactional
public class JapanWHT21940000DataRepositoryCustomImpl extends QueryDslRepositorySupport implements JapanWHT21940000DataRepositoryCustom {
public JapanWHT21940000DataRepositoryCustomImpl(Class<?> domainClass) {
super(domainClass);
// TODO Auto-generated constructor stub
}
#PersistenceContext
private EntityManager entityManager;
#Override
public List<WHT21940000Royalties> findLocalCcyAmtsByRemarks() {
QWHT21940000Data wht21940000Data = QWHT21940000Data.wHT21940000Data;
JPAQuery<WHT21940000Royalties> query = new JPAQuery<WHT21940000Royalties>(entityManager);
query.from(wht21940000Data).groupBy(wht21940000Data.remarks).select(wht21940000Data.remarks, wht21940000Data.localCcyAmt.sum());
return null;
}
}
Spring data JPA interface:
public interface JapanWHT21940000DataRepository
extends JpaRepository<WHT21940000Data, Long>,
QueryDslPredicateExecutor<WHT21940000Data>,
JapanWHT21940000DataRepositoryCustom {
}
and in DAO class:
#Repository
#Transactional("japanWhtTransactionManager")
public class JapanWHTDaoImpl implements JapanWHTDao {
#Autowired
JapanWHT21940000DataRepository wht21940000DataRepo;
// more code to follow...
EDIT: Or is there a simpler and better way to do group by query in Spring data JPA + Query DSL than what I am trying?
I think that the real issue is executing custom querydsl queries from JpaRepositories, though I have to suggest using a custom extended base repository class, as following.
First, comes the extended base repository class.
#NoRepositoryBean
public interface ExtendedQueryDslJpaRepository<T, ID extends Serializable> extends JpaRepository<T, ID>, QueryDslPredicateExecutor<T> {
<T1> Page<T1> findAll(JPQLQuery jpqlQuery, Pageable pageable);
}
And related implementation.
public class ExtendedQueryDslJpaRepositoryImpl<T, ID extends Serializable>
extends QueryDslJpaRepository<T, ID> implements ExtendedQueryDslJpaRepository<T, ID> {
private static final EntityPathResolver DEFAULT_ENTITY_PATH_RESOLVER = SimpleEntityPathResolver.INSTANCE;
private final EntityPath<T> path;
private final PathBuilder<T> builder;
private final Querydsl querydsl;
private EntityManager entityManager;
public ExtendedQueryDslJpaRepositoryImpl(JpaEntityInformation<T, ID> entityInformation, EntityManager entityManager) {
this(entityInformation, entityManager, DEFAULT_ENTITY_PATH_RESOLVER);
}
public ExtendedQueryDslJpaRepositoryImpl(JpaEntityInformation<T, ID> entityInformation, EntityManager entityManager, EntityPathResolver
resolver) {
super(entityInformation, entityManager);
this.path = resolver.createPath(entityInformation.getJavaType());
this.builder = new PathBuilder(this.path.getType(), this.path.getMetadata());
this.querydsl = new Querydsl(entityManager, this.builder);
this.entityManager = entityManager;
}
#Override
public <T1> Page<T1> findAll(JPQLQuery jpqlQuery, Pageable pageable) {
final JPQLQuery<?> countQuery = jpqlQuery;
JPQLQuery<T1> query = querydsl.applyPagination(pageable, jpqlQuery);
return PageableExecutionUtils.getPage(query.fetch(), pageable, countQuery::fetchCount);
}
}
The above classes could be placed in a configuration package.
Then, we define ExtendedQueryDslJpaRepositoryImpl as default class from which JpaRepository classes should extend, as following:
#Configuration
#EnableJpaRepositories(basePackageClasses = Application.class, repositoryBaseClass = ExtendedQueryDslJpaRepositoryImpl.class)
public class JpaConfig {
#PersistenceContext
private EntityManager entityManager;
#Bean
public JPAQueryFactory jpaQueryFactory() {
return new JPAQueryFactory(entityManager);
}
}
The next step is to define a repository for an Entity of the application, eg. CustomEntity.
public interface CustomRepository extends ExtendedQueryDslJpaRepository<CustomEntity, Long>, CustomRepositorySupport {
}
Next we define interface CustomRepositorySupport for the custom methods definition.
public interface CustomRepositorySupport {
JPQLQuery<CustomListDto> createCustomIndexQuery();
}
And finally the custom repository implementation.
#Repository
public class CustomRepositoryImpl implements CustomRepositorySupport {
private JPAQueryFactory queryFactory;
#Autowired
public CustomRepositoryImpl(JPAQueryFactory queryFactory) {
this.queryFactory = queryFactory;
}
#Override
public JPQLQuery<CustomListDto> createCustomIndexQuery() {
QCustomEntity qCustomEntity = QCustomEntity.customEntity;
BooleanBuilder predicate = new BooleanBuilder();
// Create predicate as desired
// predicate.and(...);
// Create projection of fields
/* FactoryExpression<CustomListDto> factoryExpression = Projections.bean(CustomListDto.class,
qCustomEntity.fieldA,
qCustomEntity.fieldB,
qCustomEntity.fieldC,
qCustomEntity.fieldD,
qCustomEntity.fieldE,
qCustomEntity.fieldF); */
return queryFactory.from(qCustomEntity).select(factoryExpression).where(predicate);
}
}
And the final step is to actually call the method from a Service class as following.
public interface CustomFinder {
Page<CustomListDto> findIndex(Pageable pageable);
}
-
#Service
public class CustomFinderImpl implements CustomFinder {
private CustomRepository customRepository;
#Autowired
public CustomFinderImpl(CustomRepository customRepository) {
this.customRepository = customRepository;
}
#Override
public Page<CustomListDto> findIndex(Pageable pageable) {
JPQLQuery<CustomListDto> query = customRepository.createCustomIndexQuery();
return customRepository.findAll(query, pageable);
}
}
The same way we implemented public <T1> List<T1> findAll(JPQLQuery query, FactoryExpression<T1> factoryExpression), we can simply implement required desirable methods as public <T1> List<T1> findAll(JPQLQuery query, FactoryExpression<T1> factoryExpression), <T1> List<T1> findList(JPQLQuery query, FactoryExpression<T1> factoryExpression) etc.
This way, we add capabilities to all our repositories, in order to take advantage of all types of querydsl queries, not only group by or projections.
It might seem a little over-complicated, but if you choose to implement it, and see how it works in action, you would stick to it. It is being used successfully in real apps, providing access to projection queries (without loading full entities where they are not needed), paging queries, exists subqueries etc.
Finally, using a kind of central base repository class is a kind of reusable code which is written only once.
Hope that helps.
Related
I have made this class which creates bundle from database records.
The records are got from stored procedures and names of this procedures are taken from ServiceConfig instance which is Spring #Configuration.
Now I use java Map to bind each DB entity class with according ServiceConfig method.
I would like to extend it and use Enum instead of procNameSupplier here. Is it possible to access ServiceConfig from enum?
#Component
public class BundleMaker {
#PersistenceContext
private final EntityManager entityManager;
private final Map<Class<? extends IRecord>, Supplier<String>> procNameSupplier = new HashMap<>();
public BundleMaker(EntityManager entityManager, ServiceConfig config) {
this.entityManager = entityManager;
procNameSupplier.put(MainDepRecord.class, config::mainDepProc);
//...
}
public <T extends IRecord> Bundle bundle(Class<T> cl) {
StoredProcedureQuery query;
query = entityManager.createStoredProcedureQuery(procNameSupplier.get(cl).get(), cl)
.registerStoredProcedureParameter(1, cl, REF_CURSOR);
List<T> resultList = query.getResultList();
List<Resource> resources = resultList.stream()
.map(T::toResource)
.collect(Collectors.toList());
return new Bundle(resources);
}
}
I have created two entites (RegularEmployee and ContactEntity) that extends the Employee entity.
#Entity
#Table(name="employees")
#Inheritance(strategy = InheritanceType.SINGLE_TABLE)
#DiscriminatorColumn(name = "type", discriminatorType = DiscriminatorType.STRING)
#DiscriminatorValue(value="employee")
public class Employee {
#Id
#GeneratedValue
private Long id;
private String name;
...
Im using SINGLE_TABLE inheritance for this implementations, and created a generic JpaRepository for manipulating data:
#Repository
public interface EmployeeRepository<T extends Employee> extends JpaRepository<T, Long> {
}
I've created also the Service class that autowire three instance of these generic repositories, and specific methods for each class.
#Service
public class EmployeeService {
#Autowired
private EmployeeRepository<Employee> employeeRepo;
#Autowired
private EmployeeRepository<RegularEmployee> regularRepo;
#Autowired
private EmployeeRepository<ContractEmployee> contractRepo;
public List<Employee> getAllEmployee() {
return employeeRepo.findAll();
}
public List<RegularEmployee> getAllRegularEmployee(){
return regularRepo.findAll();
}
public List<ContractEmployee> getAllContractEmployee() {
return contractRepo.findAll();
}
...
My problem is, that when I try to find all regular employees or contract employees, I always get all type of employees (employees, regular employees and contract employees all together).
I do not know why it behaves like this, even though the method's signature says it returns the appropriate type.
One option is to use #Query in EmployeeRepository:
public interface EmployeeRepository<T extends Employee> extends JpaRepository<T, Long> {
#Query("from RegularEmployee")
List<RegularEmployee> findAllRegularEmployees();
}
A second option is to create an additional repository for each subclass of Employee. For RegularEmployee would be:
public interface RegularEmployeeRepository extends EmployeeRepository<RegularEmployee>{}
This is how to use both options in EmployeeService:
#Service
public class EmployeeService {
#Autowired EmployeeRepository<Employee> employeeRepo;
#Autowired EmployeeRepository<RegularEmployee> regularRepoT;
#Autowired RegularEmployeeRepository regularRepo;
#PostConstruct
public void init(){
employeeRepo.save(new ContractEmployee("Mark"));
employeeRepo.save(new RegularEmployee("Luke"));
employeeRepo.findAll().forEach(System.out::println); // prints Mark and Luke
regularRepo.findAll().forEach(System.out::println); // prints only Luke
regularRepoT.findAllRegularEmployees().forEach(System.out::println); // prints only Luke
}
//...
}
Also you can omit #Repository on top of EmployeeRepository. Spring already knows that is a Repository because it extends JpaRepository.
Side note: if you don't need EmployeeRepository to be created by Spring add #NoRepositoryBean on top of its class.
I've been able to replicate what you've encountered using your generic EmployeeRepository. As an alternative I created two separate repositories: ContractualEmployeeRepository and RegularEmployeeRepository.
public interface ContractualEmployeeRepository extends JpaRepository<ContractualEmployee, String> {
}
public interface RegularEmployeeRepository extends JpaRepository<RegularEmployee, String> {
}
Then, I created an integration test.
#RunWith(SpringJUnit4ClassRunner.class)
#ContextConfiguration(classes = {Main.class})
#TestExecutionListeners({DependencyInjectionTestExecutionListener.class,
TransactionalTestExecutionListener.class,
DbUnitTestExecutionListener.class})
#TestPropertySource(locations="classpath:application-test.properties")
#DatabaseSetup("classpath:SingleTableDataSet.xml")
public class IntegrationTest {
#Autowired
private RegularEmployeeRepository regularEmployeeRepository;
#Autowired
private ContractualEmployeeRepository contractualEmployeeRepository;
#Test
public void test() {
Assert.assertEquals(6, regularEmployeeRepository.findAll().size());
Assert.assertEquals(4, contractualEmployeeRepository.findAll().size());
}
}
and it works.
As for the usage and limitations of Generics in Spring Data JPA repositories: https://stackoverflow.com/a/19443031/14180014 He had done a great job explaining it.
Context:
I used queryDSL in API controller which binds query to the database get. Currently, I have two tables with OneToOne relationship, and we can call them Table A and Table B. If there are 3 rows in A and 2 rows in B, when I get list A with some conditions, and the queryDSL will generate query SQL like A CROSS JOIN B WHERE A.id=B.a_id, but it will miss one item in A. Thus, I am going to implement custom repository to support change join type when generating the SQL statement. The following is some parts of my code:
(Table A is named LabelTask and Table B is named AuditTask)
and generated sql segment is
from
label_task labeltask0_ cross
join
audit_task audittask1_
where
labeltask0_.id=audittask1_.label_task
Is there something wrong with my code or is there another good solution for this situation?
JoinDescriptor.java
public class JoinDescriptor {
public final EntityPath path;
public final JoinType type;
private JoinDescriptor(EntityPath path, JoinType type) {
this.path = path;
this.type = type;
}
public static JoinDescriptor innerJoin(EntityPath path) {
return new JoinDescriptor(path, JoinType.INNERJOIN);
}
public static JoinDescriptor join(EntityPath path) {
return new JoinDescriptor(path, JoinType.JOIN);
}
public static JoinDescriptor leftJoin(EntityPath path) {
return new JoinDescriptor(path, JoinType.LEFTJOIN);
}
public static JoinDescriptor rightJoin(EntityPath path) {
return new JoinDescriptor(path, JoinType.RIGHTJOIN);
}
public static JoinDescriptor fullJoin(EntityPath path) {
return new JoinDescriptor(path, JoinType.FULLJOIN);
}
}
JoinFetchCapableQueryDslJpaRepositoryFactoryBean.java
public class JoinFetchCapableQueryDslJpaRepositoryFactoryBean<R extends JpaRepository<T, I>, T, I extends Serializable>
extends JpaRepositoryFactoryBean<R, T, I> {
public JoinFetchCapableQueryDslJpaRepositoryFactoryBean(Class<? extends R> repositoryInterface) {
super(repositoryInterface);
}
protected RepositoryFactorySupport createRepositoryFactory(EntityManager entityManager) {
return new JoinFetchCapableQueryDslJpaRepositoryFactory(entityManager);
}
private static class JoinFetchCapableQueryDslJpaRepositoryFactory<T, I extends Serializable> extends JpaRepositoryFactory {
private EntityManager entityManager;
public JoinFetchCapableQueryDslJpaRepositoryFactory(EntityManager entityManager) {
super(entityManager);
this.entityManager = entityManager;
}
protected Object getTargetRepository(RepositoryMetadata metadata) {
return new JoinFetchCapableRepositoryImpl<>(getEntityInformation(metadata.getDomainType()), entityManager);
}
protected Class<?> getRepositoryBaseClass(RepositoryMetadata metadata) {
return JoinFetchCapableRepository.class;
}
}
}
JoinFetchCapableRepository.java
#NoRepositoryBean
public interface JoinFetchCapableRepository<T, ID extends Serializable> extends
JpaRepository<T, ID>,
QuerydslPredicateExecutor<T> {
Page<T> findAll(Predicate predicate,
Pageable pageable,
JoinDescriptor... joinDescriptors);
}
JoinFetchCapableRepositoryImpl.java
public class JoinFetchCapableRepositoryImpl <T, ID extends Serializable>
extends QuerydslJpaRepository<T, ID>
implements JoinFetchCapableRepository<T, ID> {
private static final EntityPathResolver DEFAULT_ENTITY_PATH_RESOLVER = SimpleEntityPathResolver.INSTANCE;
private final EntityPath<T> path;
private final PathBuilder<T> builder;
private final Querydsl querydsl;
public JoinFetchCapableRepositoryImpl(JpaEntityInformation<T, ID> entityInformation,
EntityManager entityManager) {
this(entityInformation, entityManager, DEFAULT_ENTITY_PATH_RESOLVER);
}
public JoinFetchCapableRepositoryImpl(JpaEntityInformation<T, ID> entityInformation,
EntityManager entityManager,
EntityPathResolver resolver) {
super(entityInformation, entityManager, resolver);
this.path = resolver.createPath(entityInformation.getJavaType());
this.builder = new PathBuilder<>(path.getType(), path.getMetadata());
this.querydsl = new Querydsl(entityManager, builder);
}
#Override
public Page<T> findAll(Predicate predicate, Pageable pageable, JoinDescriptor... joinDescriptors) {
JPQLQuery countQuery = createQuery(predicate);
JPQLQuery query = querydsl.applyPagination(pageable, createFetchQuery(predicate, joinDescriptors));
Long total = countQuery.fetchCount();
List<T> content = total > pageable.getOffset()
? query.fetch()
: Collections.emptyList();
return new PageImpl<>(content, pageable, total);
}
private JPQLQuery createFetchQuery(Predicate predicate, JoinDescriptor... joinDescriptors) {
JPQLQuery query = querydsl.createQuery(path);
for(JoinDescriptor joinDescriptor: joinDescriptors)
join(joinDescriptor, query);
return (JPQLQuery) query.where(predicate);
}
private JPQLQuery join(JoinDescriptor joinDescriptor, JPQLQuery query) {
switch(joinDescriptor.type) {
case DEFAULT:
throw new IllegalArgumentException("cross join not supported");
case INNERJOIN:
query.innerJoin(joinDescriptor.path);
break;
case JOIN:
query.join(joinDescriptor.path);
break;
case LEFTJOIN:
query.leftJoin(joinDescriptor.path);
break;
case RIGHTJOIN:
query.rightJoin(joinDescriptor.path);
break;
case FULLJOIN:
query.join(joinDescriptor.path);
break;
}
return query.fetchAll();
}
}
JpaConfig.java
#Configuration
#EnableJpaRepositories(
basePackages = "com.some.company.service.repository",
repositoryFactoryBeanClass =JoinFetchCapableQueryDslJpaRepositoryFactoryBean.class)
public class JpaConfig {}
LabelTaskRepository
#Repository
public interface LabelTaskRepository extends
JoinFetchCapableRepository<LabelTask, String>,
QuerydslBinderCustomizer<QLabelTask> {
#Override
default void customize(QuerydslBindings bindings, QLabelTask qLabelTask){
this.bindQueryByTaskType(bindings, qLabelTask);
this.bindQueryByCreatedDateRange(bindings, qLabelTask);
// TODO: should remove this when task could be able to assign
bindings.excluding(qLabelTask.status);
}
...
}
Result:
when I launch the spring application, It will return the following error message:
Caused by: org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'auditTaskController' defined in file [/.../some/company/service/controllers/AuditTaskController.class]: Unsatisfied dependency expressed through constructor parameter 0; nested exception is org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'auditTaskService' defined in file [/.../some/company/service/AuditTaskService.class]: Unsatisfied dependency expressed through constructor parameter 0; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'auditTaskRepository': Invocation of init method failed; nested exception is java.lang.IllegalStateException: No suitable constructor found on interface some.company.utils.JoinFetchCapableRepository to match the given arguments: [class org.springframework.data.jpa.repository.support.JpaMetamodelEntityInformation, class com.sun.proxy.$Proxy182]. Make sure you implement a constructor taking these
at org.springframework.beans.factory.support.ConstructorResolver.createArgumentArray(ConstructorResolver.java:733)
at org.springframework.beans.factory.support.ConstructorResolver.autowireConstructor(ConstructorResolver.java:198)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.autowireConstructor(AbstractAutowireCapableBeanFactory.java:1266)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBeanInstance(AbstractAutowireCapableBeanFactory.java:1123)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:535)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:495)
at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:317)
at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:222)
at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:315)
at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:199)
at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:759)
at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:867)
at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:548)
at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:754)
at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:386)
at org.springframework.boot.SpringApplication.run(SpringApplication.java:307)
at org.springframework.boot.test.context.SpringBootContextLoader.loadContext(SpringBootContextLoader.java:127)
at org.springframework.test.context.cache.DefaultCacheAwareContextLoaderDelegate.loadContextInternal(DefaultCacheAwareContextLoaderDelegate.java:99)
at org.springframework.test.context.cache.DefaultCacheAwareContextLoaderDelegate.loadContext(DefaultCacheAwareContextLoaderDelegate.java:117)
No suitable constructor found on interface
some.company.utils.JoinFetchCapableRepository to match the given
arguments: [class
org.springframework.data.jpa.repository.support.JpaMetamodelEntityInformation,
class com.sun.proxy.$Proxy182].
Based on the exception message, JoinFetchCapableRepositoryImpl needs a constructor which receives two parameters: JpaMetamodelEntityInformation, $Proxy182.
I added a constructor like this:
public JoinFetchCapableRepositoryImpl(
JpaMetamodelEntityInformation<T, ID> entityInformation,
EntityManager entityManager) {
this(entityInformation, entityManager, DEFAULT_ENTITY_PATH_RESOLVER);
}
After this, It works for me and is able to change join type for query dsl
i have created a Base entity interface with getId() method and implemented into
entities for doing crud operations on all entity save is works and
delete,update also work but retriving by id doesnt work i am not sure its
possible or not if possible then suggest or any other way.
this is base interface for all entities and getId() overrides in each entity
public interface DemoEntity extends Serializable {
public long getId();
}
this is an user entity
public class User implements Serializable,DemoEntity {
getter/setters
}
public class Subject implements Serializable,DemoEntity {
getter/setters
}
//this is modelmanager class for doing crud operations
public class ModelManager {
#Autowired
#PersistenceContext
private EntityManager em;
#Transactional
public void save(DemoEntity entity) {
em.persist(entity);
}
#Transactional
public DemoEntity getEntityById(long id) {
DemoEntity de=em.find(DemoEntity.class, id);
return de;
}
}
#Autowired <-- is not necessary
#PersistenceContext
private EntityManager em;
Your method would looks like better
#Transactional
public DemoEntity getEntityById(long id) {
return em.find(DemoEntity.class, id);
}
and on the top of the class you need to put an annotation like #Component #Repository
And finally you did not say what kind of error you got
So I have a number of generics in Spring 3.2 and ideally my architecture would look something like this.
class GenericDao<T>{}
class GenericService<T, T_DAO extends GenericDao<T>>
{
// FAILS
#Autowired
T_DAO;
}
#Component
class Foo{}
#Repository
class FooDao extends GenericDao<Foo>{}
#Service
FooService extends GenericService<Foo, FooDao>{}
Unfortunately with multiple implementations of the generics the autowiring throws an error about multiple matching bean definitions. I assume this is because #Autowired processes before type erasure. Every solution I've found or come up with looks ugly to me or just inexplicably refuses to work. What is the best way around this problem?
How about adding a constructor to the GenericService and move the autowiring to the extending class, e.g.
class GenericService<T, T_DAO extends GenericDao<T>> {
private final T_DAO tDao;
GenericService(T_DAO tDao) {
this.tDao = tDao;
}
}
#Service
FooService extends GenericService<Foo, FooDao> {
#Autowired
FooService(FooDao fooDao) {
super(fooDao);
}
}
Update:
As of Spring 4.0 RC1, it is possible to autowire based on generic type, which means that you can write a generic service like
class GenericService<T, T_DAO extends GenericDao<T>> {
#Autowired
private T_DAO tDao;
}
and create multiple different Spring beans of it like:
#Service
class FooService extends GenericService<Foo, FooDao> {
}
Here is a closest solution. The specialized DAOs are annotated at the business layer. As in the question from OP, the best effort would be having an annotated DAO in the EntityDAO generic template itself. Type erasure seems to be not allowing the specialized type information to get passed onto the spring factories [resulting in reporting matching beans from all the specialized DAOs]
The Generic Entity DAO template
public class EntityDAO<T>
{
#Autowired
SessionFactory factory;
public Session getCurrentSession()
{
return factory.getCurrentSession();
}
public void create(T record)
{
getCurrentSession().save(record);
}
public void update(T record)
{
getCurrentSession().update(record);
}
public void delete(T record)
{
getCurrentSession().delete(record);
}
public void persist(T record)
{
getCurrentSession().saveOrUpdate(record);
}
public T get(Class<T> clazz, Integer id)
{
return (T) getCurrentSession().get(clazz, id);
}
}
The Generic Entity Based Business Layer Template
public abstract class EntityBusinessService<T>
implements Serializable
{
public abstract EntityDAO<T> getDAO();
//Rest of code.
}
An Example Specialized Entity DAO
#Transactional
#Repository
public class UserDAO
extends EntityDAO<User>
{
}
An Example Specialized Entity Business Class
#Transactional
#Service
#Scope("prototype")
public class UserBusinessService
extends EntityBusinessService<User>
{
#Autowired
UserDAO dao;
#Override
public EntityDAO<User> getDAO()
{
return dao;
}
//Rest of code
}
You can remove the #autowire annotation and perform delayed “autowire” using #PostConstruct and ServiceLocatorFactoryBean.
Your GenericService will look similar to this
public class GenericService<T, T_DAO extends GenericDao<T>>{
#Autowired
private DaoLocator daoLocatorFactoryBean;
//No need to autowried, autowireDao() will do this for you
T_DAO dao;
#SuppressWarnings("unchecked")
#PostConstruct
protected void autowireDao(){
//Read the actual class at run time
final Type type;
type = ((ParameterizedType) getClass().getGenericSuperclass())
.getActualTypeArguments()[1];
//figure out the class of the fully qualified class name
//this way you can know the bean name to look for
final String typeClass = type.toString();
String daoName = typeClass.substring(typeClass.lastIndexOf('.')+1
,typeClass.length());
daoName = Character.toLowerCase(daoName.charAt(0)) + daoName.substring(1);
this.dao = (T_DAO) daoLocatorFactoryBean.lookup(daoName);
}
daoLocatorFactoryBean does the magic for you.
In order to use it you need to add an interface similar to the one below:
public interface DaoLocator {
public GenericDao<?> lookup(String serviceName);
}
You need to add the following snippet to your applicationContext.xml
<bean id="daoLocatorFactoryBean"
class="org.springframework.beans.factory.config.ServiceLocatorFactoryBean">
<property name="serviceLocatorInterface"
value="org.haim.springframwork.stackoverflow.DaoLocator" />
</bean>
This is a nice trick and it will save you little boilerplate classes.
B.T.W I do not see this boilerplate code as a big issue and the project I working for uses matsev approach.
Why do you want a generic service ? Service classes are meant for specific units of work involving multple entities. You can just inject a repository straight into a controller.
Here is an example of generic repository with constructor argument, you could also make each method Generic instead and have no constructor argument. But each method call would require class as parameter:
public class DomainRepository<T> {
#Resource(name = "sessionFactory")
protected SessionFactory sessionFactory;
public DomainRepository(Class genericType) {
this.genericType = genericType;
}
#Transactional(readOnly = true)
public T get(final long id) {
return (T) sessionFactory.getCurrentSession().get(genericType, id);
}
Example of bean definition for the generic repository - you could have multple different beans, using different contstructor args.
<bean id="tagRepository" class="com.yourcompnay.data.DomainRepository">
<constructor-arg value="com.yourcompnay.domain.Tag"/>
</bean>
Depdncy injection of bean using resource annotation
#Resource(name = "tagRepository")
private DomainRepository<Tag> tagRepository;
And this allows the Domainreposiroty to be subclassed for specific entities/methods, which woul dallow autowiring :
public class PersonRepository extends DomainRepository<Person> {
public PersonRepository(){
super(Person.class);
}
...
You should use autowiring in classes which extends these generics
For this question one needs to understand about what autowire is. In common terms we can say that through autowire we create a object instance/bean at the time of deployment of the web app. So now going with the question if you are declaring autowiring in multiple places with the same name. Then this error comes. Autowiring can be done in multiple ways so if you are using multiple type of autowiring technique, then also one could get this error.
Complete Generic Solution using Spring 4:
Domain Class
#Component
class Foo{
}
#Component
class Bar{
}
DAO Layer
interface GenericDao<T>{
//list of methods
}
class GenericDaoImpl<T> implements GenericDao<T>{
#Autowired
SessionFactory factory;
private Class<T> domainClass; // Get Class Type of <T>
public Session getCurrentSession(){
return factory.getCurrentSession();
}
public DaoImpl() {
this.domainClass = (Class<T>) GenericTypeResolver.resolveTypeArgument(getClass(), DaoImpl.class);
}
//implementation of methods
}
interface FooDao extends GenericDao<Foo>{
//Define extra methods if required
}
interface BarDao extends GenericDao<Bar>{
//Define extra methods if required
}
#Repository
class FooDao extends GenericDaoImpl<Foo> implements FooDao{
//implementation of extra methods
}
#Repository
class BarDao extends GenericDaoImpl<Bar> implements BarDao{
//implementation of extra methods
}
Service Layer
interface GenericService<T>{
//List of methods
}
class GenericServiceImpl<T> implements GenericService<T>{
#Autowire
protected GenericDao<T> dao; //used to access DAO layer
}
class FooService extends GenericService<Foo>{
//Add extra methods of required
}
class BarService extends GenericService<Bar>{
//Add extra methods of required
}
#Service
class FooServiceImpl extends GenericServiceImpl<Foo> implements GenericService<Foo>{
//implementation of extra methods
}
#Service
class BarServiceImpl extends GenericServiceImpl<Bar> implements GenericService<Bar>{
//implementation of extra methods
}