Support for projections on repository query methods

[odrotbohm]

QueryMethods now expose a ResourceProcessor which is exposes information about the final to be created object types which can either be DTOs containing a persistence constructor (see @PersistenceConstructor) or projection interfaces. The former are analyzed for constructor properties so that store implementations can use that information to create projected queries that return exactly the fields required for that DTO.

Projection interfaces are inspected, their properties are considered input properties and the same projection queries can be issued against the data store. If a projection contains dynamically calculated properties (i.e. it uses SpEL expressions via @value) the original entities have to be queried and can be projected during post processing.

ProjectionFactory now exposes a more advanced ProjectionInformation that has additional meta information about the projection type. ProxyProjectionFactory now refers to the BeanClassLoader instead of the ResourceLoader.

RepositoryFactory(Bean)Support now also implement BeanFactoryAware to forward the BeanFactory to the SpelAwareProxyProjectionFactory which in turn now gets handed into the QueryLookupStrategy as well as the QueryMethod.

Parameter now knows about a dynamic projection type, which is a query method parameter of type Class bound to a generic method parameter and will be used to determine the projection to be used on a per call basis.

[mbragg02]

Hi @olivergierke
Im in the process of upgrading our app and I've run into an issue related to these changes and I wonder if you could advise. We are upgrading from Spring data commons from 1.11.4.RELEASE -> 1.12.x / 1.13.x.

We have a hierarchical entity structure. e.g. ReasonLabel extends AbstractResolutionLabel
We have a table with a Discriminator Column for the name of the concrete type.
We have the following query which previously worked:

@Query("SELECT label FROM AbstractResolutionLabel label WHERE label.group.id = :groupId AND label.providerType = :providerType AND TYPE(label) = :clazz")
    <T extends AbstractResolutionLabel> List<T> findByGroupIdAndProviderTypeAndType(@Param("groupId") String groupId,
                                                                                    @Param("providerType") ProviderType providerType,
                                                                                    @Param("clazz") Class<T> clazz);

We are now getting the following error:

Caused by: org.hibernate.QueryException: Named parameter [clazz] not set
	at org.hibernate.query.internal.QueryParameterBindingsImpl.verifyParametersBound(QueryParameterBindingsImpl.java:234)
	at org.hibernate.query.internal.AbstractProducedQuery.beforeQuery(AbstractProducedQuery.java:1309)
	at org.hibernate.query.internal.AbstractProducedQuery.list(AbstractProducedQuery.java:1408)
	at org.hibernate.query.Query.getResultList(Query.java:146)
	at org.springframework.data.jpa.repository.query.JpaQueryExecution$CollectionExecution.doExecute(JpaQueryExecution.java:121)
	at org.springframework.data.jpa.repository.query.JpaQueryExecution.execute(JpaQueryExecution.java:85)
	at org.springframework.data.jpa.repository.query.AbstractJpaQuery.doExecute(AbstractJpaQuery.java:116)
	at org.springframework.data.jpa.repository.query.AbstractJpaQuery.execute(AbstractJpaQuery.java:106)
	at org.springframework.data.repository.core.support.RepositoryFactorySupport$QueryExecutorMethodInterceptor.doInvoke(RepositoryFactorySupport.java:483)
	at org.springframework.data.repository.core.support.RepositoryFactorySupport$QueryExecutorMethodInterceptor.invoke(RepositoryFactorySupport.java:461)
	at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)
	at org.springframework.data.projection.DefaultMethodInvokingMethodInterceptor.invoke(DefaultMethodInvokingMethodInterceptor.java:61)
	at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)
	at org.springframework.transaction.interceptor.TransactionInterceptor$1.proceedWithInvocation(TransactionInterceptor.java:99)
	at org.springframework.transaction.interceptor.TransactionAspectSupport.invokeWithinTransaction(TransactionAspectSupport.java:282)
	at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:96)
	at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)
	at org.springframework.dao.support.PersistenceExceptionTranslationInterceptor.invoke(PersistenceExceptionTranslationInterceptor.java:136)
	... 57 more

It appears that from this line: https://github.com/spring-projects/spring-data-commons/pull/150/files#diff-325a1f477d275feb68e9ffec76dc064eR200 the new isDynamicProjectionParameter is returning true, so the class parameter is not being bound - Because both the parameter type and return type (T) are both equal.

I appreciate this change has been here for some time now, so I will likely have to change my app code.. but was hoping you could possibly suggest an alternative for my scenario.
Many thanks

[schauder]

With a quick glance at it, this sounds like a bug. Can you create a proper issue in Jira (https://jira.spring.io), please?

[mbragg02]

Thanks @schauder I created an issue: https://jira.spring.io/browse/DATACMNS-1002 cc @olivergierke