Data Module

Overview

The Data module provides capabilities for implementing repository patterns and thereby simplifying the repository layer. Repository patterns are ideal for simple queries that require boilerplate code, enabling cenertalization of query logic and consequently reducing code duplication and improving testability.

The code sample below gives you a quick overview on the common usage scenarios of the data module:

@Repository
public interface PersonRepository extends EntityRepository<Person, Long>
{

    List<Person> findByAgeBetweenAndGender(int minAge, int maxAge, Gender gender);

    @Query("select p from Person p where p.ssn = ?1")
    Person findBySSN(String ssn);

    @Query(named=Person.BY_FULL_NAME)
    Person findByFullName(String firstName, String lastName);

}

As you see in the sample, there are several usage scenarios outlined here:

  • Declare a method which executes a query by simply translating its name and parameters into a query.

  • Declare a method which automatically executes a given JPQL query string with parameters.

  • Declare a method which automatically executes a named query with parameters.

The implementation of the method is done automatically by the CDI extension. A client can declare a dependency to the interface only. The details on how to use those features are outlines in the following chapters.

Project Setup

The configuration information provided here is for Maven-based projects and it assumes that you have already declared the DeltaSpike version and DeltaSpike Core module for your projects, as detailed in Configure DeltaSpike in Your Projects. For Maven-independent projects, see Configure DeltaSpike in Maven-independent Projects.

1. Declare Data Module Dependencies

Add the Data module to the list of dependencies in the project pom.xml file using this code snippet:

<dependency>
    <groupId>org.apache.deltaspike.modules</groupId>
    <artifactId>deltaspike-data-module-api</artifactId>
    <version>${deltaspike.version}</version>
    <scope>compile</scope>
</dependency>

<dependency>
    <groupId>org.apache.deltaspike.modules</groupId>
    <artifactId>deltaspike-data-module-impl</artifactId>
    <version>${deltaspike.version}</version>
    <scope>runtime</scope>
</dependency>

Or if you’re using Gradle, add these dependencies to your build.gradle:

     runtime 'org.apache.deltaspike.modules:deltaspike-data-module-impl'
     compile 'org.apache.deltaspike.modules:deltaspike-data-module-api'

2. Complete Additional Java Environment Configuration

The Data module requires a JPA implementation to be available in the Java environment where your projects are deployed.

The simplest way using the DeltaSpike Data module is to run your application in a Java EE container supporting at least the Java EE6 Web Profile. Other configurations like running it inside Tomcat or even a Java SE application should be possible - you need to include a JPA provider as well as a CDI container to your application manually.

As of DeltaSpike v1.4.0, the Data module internally leverages the Proxy module, which wraps ASM 5. No external dependencies required, and now we have full support for interceptors on partial beans.

3. Complete Additional Project Configuration

DeltaSpike Data requires an EntityManager exposed via a CDI producer - which is common practice in Java EE6 applications.

public class EntityManagerProducer
{
    @PersistenceUnit
    private EntityManagerFactory emf;

    @Produces // you can also make this @RequestScoped
    public EntityManager create()
    {
        return emf.createEntityManager();
    }

    public void close(@Disposes EntityManager em)
    {
        if (em.isOpen())
        {
            em.close();
        }
    }
}

This allows the EntityManager to be injected over CDI instead of only being used with a @PersistenceContext annotation. Using multiple EntityManager is explored in more detail in a following section.

If you use a JTA DataSource with your EntityManager, you also have to configure the TransactionStrategy your repositories use. Adapt your beans.xml for this:

<beans>
    <alternatives>
        <class>org.apache.deltaspike.jpa.impl.transaction.BeanManagedUserTransactionStrategy</class>
    </alternatives>
</beans>
Using the DeltaSpike Data module in an EAR deployment is currently restricted to annotation-based entities.

Core Concepts

Repositories

With the DeltaSpike Data module, it is possible to make a repository out of basically any abstract class or interface (using a concrete class will work too, but you will not be able to use most of the CDI extension features). All that is required is to mark the type as such with a simple annotation:

@Repository(forEntity = Person.class)
public abstract class PersonRepository {
    ...
}

@Repository(forEntity = Person.class)
public interface PersonRepository {
    ...
}

The @Repository annotation tells the extension that this is a repository for the Person entity. Any method defined on the repository will be processed by the framework. The annotation does not require to set the entity class (we’ll see later why) but if there are just plain classes or interfaces this is the only way to tell the framework what entity the repository relates to. In order to simplify this, DeltaSpike Data provides several base types.

The EntityRepository Interface

Although mainly intended to hold complex query logic, working with both a repository and an EntityManager in the service layer might unnecessarily clutter code. In order to avoid this for the most common cases, DeltaSpike Data provides base types which can be used to replace the entity manager.

The top base type is the EntityRepository interface, providing common methods used with an EntityManager. The following code shows the most important methods of the interface:

public interface EntityRepository<E, PK extends Serializable>
{

    E save(E entity);

    void remove(E entity);

    void refresh(E entity);

    void flush();

    E findBy(PK primaryKey);

    List<E> findAll();

    List<E> findBy(E example, SingularAttribute<E, ?>... attributes);

    List<E> findByLike(E example, SingularAttribute<E, ?>... attributes);

    Long count();

    Long count(E example, SingularAttribute<E, ?>... attributes);

    Long countLike(E example, SingularAttribute<E, ?>... attributes);

}

The concrete repository can then extend this basic interface. For our Person repository, this might look like the following:

@Repository
public interface PersonRepository extends EntityRepository<Person, Long>
{

    Person findBySsn(String ssn);

}
Annotations on interfaces do not inherit. If the EntityRepository interface is extended by another interface adding some more common methods, it is not possible to simply add the annotation there. It needs to go on each concrete repository. The same is not true if a base class is introduced, as we see in the next chapter.
The AbstractEntityRepository Class

This class is an implementation of the EntityRepository interface and provides additional functionality when custom query logic needs also to be implemented in the repository.

public abstract class PersonRepository extends AbstractEntityRepository<Person, Long>
{

    public List<Person> findBySSN(String ssn)
    {
        return typedQuery("select p from Person p where p.ssn = ?1")
                .setParameter(1, ssn)
                .getResultList();
    }

}

Deactivating Repositories

Repositories can be deactivated creating a ClassDeactivator.

The EntityRepository interface implements the Deactivatable interface allowing it to be used in the ClassDeactivator.

If your repository does not implement EntityRepository and you want to deactivate it, you will need to implement the Deactivatable interface yourself.

@Repository(forEntity = Person.class)
public abstract class PersonRepository implements Deactivatable {
    ...
}

@Repository(forEntity = Person.class)
public interface PersonRepository implements Deactivatable{
    ...
}

Support of @TransactionScoped EntityManagers

For using @TransactionScoped beans like a @TransactionScoped-EntityManager, you need to annotate the Data-repository with @Transactional explicitly or one of the beans in the call-hierarchy. That’s needed, because the context bound to @TransactionScoped needs to be active, before the @TransactionScoped-EntityManager gets resolved (internally).

The following examples illustrate the described usages:

@TransactionScoped EntityManager combined with a simple repository
public class EntityManagerProducer
{
    @Produces
    @TransactionScoped
    public EntityManager create() { ... }

    public void close(@Disposes EntityManager em)  { ... }
}

@ApplicationScoped
public class MyService
{
    @Inject
    private MyRepository myRepository;

    public void create()
    {
        //...
        this.myRepository.save(...); //executed in a transaction
        //...
    }
}

@Transactional
@Repository
public interface MyRepository extends EntityRepository<MyEntity, String>
{
  //...
}
@TransactionScoped EntityManager combined with a simple repository called by a transactional bean
public class EntityManagerProducer
{
    @Produces
    @TransactionScoped
    public EntityManager create() { ... }

    public void close(@Disposes EntityManager em)  { ... }
}

@Transactional
@ApplicationScoped
public class MyService
{
    @Inject
    private MyRepository myRepository;

    public void create() //executed in a transaction
    {
        //...
        this.myRepository.save(...);
        //...
    }
}

@Repository
public interface MyRepository extends EntityRepository<MyEntity, String>
{
  //...
}

Using Multiple EntityManagers

While most applications will run just fine with a single EntityManager, there might be setups where multiple data sources are used. This can be configured with the EntityManagerConfig annotation:

@Repository
@EntityManagerConfig(entityManagerResolver = CrmEntityManagerResolver.class, flushMode = FlushModeType.COMMIT)
public interface PersonRepository extends EntityRepository<Person, Long>
{
    ...
}

public class CrmEntityManagerResolver implements EntityManagerResolver
{
    @Inject @CustomerData // Qualifier - assumes a producer is around...
    private EntityManager em;

    @Override
    public EntityManager resolveEntityManager()
    {
        return em;
    }
}

Again, note that annotations on interfaces do not inherit, so it is not possible to create something like a base CrmRepository interface with the @EntityManagerConfig and then extending / implementing this interface.

Other EntityManager Methods

While the EntityRepository methods should cover most interactions normally done with an EntityManager, for some specific cases it might still be useful to have one or the other method available. For this case, it is possible to extend / implement the EntityManagerDelegate interface for repositories, which offers most other methods available in a JPA 2.0 EntityManager:

@Repository
public interface PersonRepository extends EntityRepository<Person, Long>, EntityManagerDelegate<Person>
{
    ...
}

Alternatively, you can extend the FullEntityRepository interface which is a short-hand for extending all of EntityRepository, EntityManagerDelegate and CriteriaSupport.

@Repository
public interface PersonRepository extends FullEntityRepository<Person, Long>
{
    ...
}

For abstract classes, there is a convenience base class AbstractFullEntityRepository which also implements EntityManagerDelegate and CriteriaSupport and thus exposes most EntityManager methods:

@Repository
public abstract PersonRepository extends AbstractFullEntityRepository<Person, Long>
{
    ...
}

Query Method Expressions

Good naming is a difficult aspects in software engineering. A good method name usually makes comments unnecessary and states exactly what the method does. And with method expressions, the method name is actually the implementation!

Using Method Expressions

Let’s start by looking at a (simplified for readability) example:

@Entity
public class Person
{

    @Id @GeneratedValue
    private Long id;
    private String name;
    private Integer age;
    private Gender gender;

}

@Repository
public interface PersonRepository extends EntityRepository<Person, Long>
{

    List<Person> findByNameLikeAndAgeBetweenAndGender(String name,
                              int minAge, int maxAge, Gender gender);

}

Looking at the method name, this can easily be read as query all Persons which have a name like the given name parameter, their age is between a min and a max age and having a specific gender. The DeltaSpike Data module can translate method names following a given format and directly generate the query implementation out of it (in EBNF-like form):

(Entity|List<Entity>) findBy(Property[Comparator]){Operator Property [Comparator]}

Or in more concrete words:

  • The query method must either return an entity or a list of entities.

  • It must start with the findBy keyword (or related findOptionalBy, findAnyBy).

  • Followed by a property of the Repository entity and an optional comparator (we’ll define this later). The property will be used in the query together with the comparator. Note that the number of arguments passed to the method depend on the comparator.

  • You can add more blocks of property-comparator which have to be concatenated by a boolean operator. This is either an And or Or.

You can use the same way for delete an entity: * It must start with the removeBy keyword (or related deleteBy).

Other assumptions taken by the expression evaluator:

  • The property name starts lower cased while the property in the expression has an upper cases first character.

Following comparators are currently supported to be used in method expressions:

Name # of Arguments Description

Equal

1

Property must be equal to argument value. If the operator is omitted in the expression, this is assumed as default.

NotEqual

1

Property must be not equal to argument value.

Like

1

Property must be like the argument value. Use the %-wildcard in the argument.

GreaterThan

1

Property must be greater than argument value.

GreaterThanEquals

1

Property must be greater than or equal to argument value.

LessThan

1

Property must be less than argument value.

LessThanEquals

1

Property must be less than or equal to argument value.

Between

2

Property must be between the two argument values.

IsNull

0

Property must be null.

IsNotNull

0

Property must be non-null.

Note that DeltaSpike will validate those expressions during startup, so you will notice early in case you have a typo in those expressions.

Query Ordering

Beside comparators it is also possible to sort queries by using the OrderBy keyword, followed by the attribute name and the direction (Asc or Desc).

@Repository
public interface PersonRepository extends EntityRepository<Person, Long>
{

    List<Person> findByLastNameLikeOrderByAgeAscLastNameDesc(String lastName);

}

Nested Properties

To create a comparison on a nested property, the traversal parts can be separated by a _:

@Repository
public interface PersonRepository extends EntityRepository<Person, Long>
{

    List<Person> findByCompany_companyName(String companyName);

}

Query Options

DeltaSpike supports query options on method expressions. If you want to page a query, you can change the first result as well as the maximum number of results returned:

@Repository
public interface PersonRepository extends EntityRepository<Person, Long>
{

    List<Person> findByNameLike(String name, @FirstResult int start, @MaxResults int pageSize);

}

Method Prefix

In case the findBy prefix does not comply with your team conventions, this can be adapted:

@Repository(methodPrefix = "fetchWith")
public interface PersonRepository extends EntityRepository<Person, Long>
{

    List<Person> fetchWithNameLike(String name, @FirstResult int start, @MaxResults int pageSize);

}

Query Annotations

While method expressions are fine for simple queries, they will often reach their limit once things get slightly more complex. Another aspect is the way you want to use JPA: The recommended approach using JPA for best performance is over named queries. To help incorporate those use cases, the DeltaSpike Data module supports also annotating methods for more control on the generated query.

Using Query Annotations

The simples way to define a specific query is by annotating a method and providing the JPQL query string which has to be executed. In code, this looks like the following sample:

public interface PersonRepository extends EntityRepository<Person, Long>
{

    @Query("select count(p) from Person p where p.age > ?1")
    Long countAllOlderThan(int minAge);

}

The parameter binding in the query corresponds to the argument index in the method.

You can also refer to a named query which is constructed and executed automatically. The @Query annotation has a named attribute which corresponds to the query name:

@Entity
@NamedQueries({
    @NamedQuery(name = Person.BY_MIN_AGE,
                query = "select count(p) from Person p where p.age > ?1 order by p.age asc")
})
public class Person
{

    public static final String BY_MIN_AGE = "person.byMinAge";
    ...

}

@Repository
public interface PersonRepository extends EntityRepository<Person, Long>
{

    @Query(named = Person.BY_MIN_AGE)
    Long countAllOlderThan(int minAge);

}

Same as before, the parameter binding corresponds to the argument index in the method. If the named query requires named parameters to be used, this can be done by annotating the arguments with the @QueryParam annotation.

Java does not preserve method parameter names (yet), that’s why the annotation is needed.
@NamedQuery(name = Person.BY_MIN_AGE,
            query = "select count(p) from Person p where p.age > :minAge order by p.age asc")

...

@Repository
public interface PersonRepository extends EntityRepository<Person, Long>
{

    @Query(named = Person.BY_MIN_AGE)
    Long countAllOlderThan(@QueryParam("minAge") int minAge);

}

It is also possible to set a native SQL query in the annotation. The @Query annotation has a native attribute which flags that the query is not JPQL but plain SQL:

@Entity
@Table(name = "PERSON_TABLE")
public class Person
{
    ...
}

@Repository
public interface PersonRepository extends EntityRepository<Person, Long>
{

    @Query(value = "SELECT * FROM PERSON_TABLE p WHERE p.AGE > ?1", isNative = true)
    List<Person> findAllOlderThan(int minAge);

}

Annotation Options

Beside providing a query string or reference, the @Query annotation provides also two more attributes:

@Repository
public interface PersonRepository extends EntityRepository<Person, Long>
{

    @Query(named = Person.BY_MIN_AGE, max = 10, lock = LockModeType.PESSIMISTIC_WRITE)
    List<Person> findAllForUpdate(int minAge);

}
Name Description

max

Limits the number of results.

lock

Use a specific LockModeType to execute the query.

Note that these options can also be applied to method expressions.

Query Options

All the query options you have seen so far are more or less static. But sometimes you might want to apply certain query options dynamically. For example, sorting criteria could come from a user selection so they cannot be known beforehand. DeltaSpike allows you to apply query options at runtime by using the QueryResult result type:

@Repository
public interface PersonRepository extends EntityRepository<Person, Long>
{

    @Query("select p from Person p where p.age between ?1 and ?2")
    QueryResult<Person> findAllByAge(int minAge, int maxAge);

}

Once you have obtained a QueryResult, you can apply further options to the query:

List<Person> result = personRepository.findAllByAge(18, 65)
    .orderAsc("p.lastName", false)
    .orderDesc("p.age", false)
    .lockMode(LockModeType.WRITE)
    .hint("org.hibernate.timeout", Integer.valueOf(10))
    .getResultList();
Note that sorting is only applicable to method expressions or non-named queries. For named queries it might be possible, but is currently only supported for Hibernate, EclipseLink and OpenJPA.

Note that the QueryResult return type can also be used with method expressions.

QueryResult is based on our internal understanding of your query DeltaSpike expects the alias used in your queries to refer to the entity as e You can disable this behavior by passing in false with your attribute, .orderDesc("p.age", false) which would add descending ordering to your existing query select p from Person p

Pagination

We introduced the QueryResult type in the last chapter, which can also be used for pagination:

// Query API style
QueryResult<Person> paged = personRepository.findByAge(age)
    .maxResults(10)
    .firstResult(50);

// or paging style
QueryResult<Person> paged = personRepository.findByAge(age)
    .withPageSize(10) // equivalent to maxResults
    .toPage(5);

int totalPages = paged.countPages();

Bulk Operations

While reading entities and updating them one by one might be fine for many use cases, applying bulk updates or deletes is also a common usage scenario for repositories. DeltaSpike supports this with a special marking annotation @Modifying:

@Repository
public interface PersonRepository extends EntityRepository<Person, Long>
{

    @Modifying
    @Query("update Person as p set p.classifier = ?1 where p.classifier = ?2")
    int updateClassifier(Classifier current, Classifier next);

}

Bulk operation query methods can either return void or int, which counts the number of entities affected by the bulk operation.

Optional Query Results

The JPA spec requires to throw exceptions in case the getSingleResult() method does either return no or more than one result. This can result in tedious handling with try-catch blocks or have potential impact on your transaction (as the RuntimeException might roll it back).

DeltaSpike Data gives the option to change this to the way it makes most sense for the current usecase. While the default behavior is still fully aligned with JPA, it is also possible to request optional query results.

Zero or One Result

With this option, the query returns null instead of throwing a NoResultException when there is no result returned. It is usable with method expressions, Query annotations and QueryResult<E> calls.

@Repository(forEntity = Person.class)
public interface PersonRepository
{

    Person findOptionalBySsn(String ssn);

    @Query(named = Person.BY_NAME, singleResult = SingleResultType.OPTIONAL)
    Person findByName(String firstName, String lastName);

}

For method expressions, the findOptionalBy prefix can be used. For @Query annotations, the singleResult attribute can be overridden with the SingleResultType.OPTIONAL enum.

In case the query returns more than one result, a NonUniqueResultException is still thrown.

Any Result

If the caller does not really mind what kind if result is returned, it is also possible to request any result from the query. If there is no result, same as for optional queries null is returned. In case there is more than one result, any result is returned, or more concretely the first result out of the result list.

@Repository(forEntity = Person.class)
public interface PersonRepository
{

    Person findAnyByLastName(String lastName);

    @Query(named = Person.BY_NAME, singleResult = SingleResultType.ANY)
    Person findByName(String firstName, String lastName);

}

For method expressions, the findAnyBy prefix can be used. For @Query annotations, the singleResult attribute can be overridden with the SingleResultType.ANY enum.

This option will not throw an exception.

Transactions

If you call any method expression, @Query-annotated method or a method from the EntityRepository, the repository will figure out if a transaction is needed or not, and if so, if there is already one ongoing. The Data module uses the TransactionStrategy provided by the JPA Module for this. See the JPA module documentation for more details.

Some containers do not support BeanManagedUserTransactionStrategy! As JTA has still some portability issues even in Java EE 7, it might be required that you implement your own TransactionStrategy. We will think about providing an acceptable solution for this.

If you need to open a transaction on a concrete repository method, we currently recommend creating an extension (see next chapter) which uses @Transactional and might look like the following sample.

public class TxExtension<E> implements TxRepository // this is your extension interface
{
    @Inject
    private EntityManager em;

    @Override @Transactional
    public List<E> transactional(ListResultCallback callback)
    {
        return callback.execute();
    }

}

Repositories can then implement the TxRepository interface and call their queries in the transactional method (where the callback implementation can be, for example, in an anonymous class).

Extensions

Query Delegates

While repositories defines several base interfaces, there might still be the odd convenience method that is missing. This is actually intentional - things should not get overloaded for each and every use case. That’s why in DeltaSpike you can define your own reusable methods.

For example, you might want to use the QueryDsl library in your repositories:

import com.mysema.query.jpa.impl.JPAQuery;

public interface QueryDslSupport
{
    JPAQuery jpaQuery();
}

@Repository(forEntity = Person.class)
public interface PersonRepository extends QueryDslSupport
{
   ...
}

Implementing the Query Delegate

The first step is to define an interface which contains the extra methods for your repositories (as shown above):

public interface QueryDslSupport
{
    JPAQuery jpaQuery();
}

As a next step, you need to provide an implementation for this interface once. It is also important that this implementation implements the DelegateQueryHandler interface (do not worry, this is just an empty marker interface):

public class QueryDslRepositoryExtension<E> implements QueryDslSupport, DelegateQueryHandler
{

    @Inject
    private QueryInvocationContext context;

    @Override
    public JPAQuery jpaQuery()
    {
        return new JPAQuery(context.getEntityManager());
    }

}

As you see in the sample, you can inject a QueryInvocationContext which contains utility methods like accessing the current EntityManager and entity class.

Note that, if you define multiple extensions with equivalent method signatures, there is no specific order in which the implementation is selected.

Mapping

While repositories are primarily intended to work with Entities, it might be preferable in some cases to have an additional mapping layer on top of them, for example because the Entities are quite complex but the service layer needs only a limited view on it, or because the Entities are exposed over a remote interface and there should not be a 1:1 view on the domain model.

DeltaSpike Data allows to directly plugin in such a mapping mechanism without the need to specify additional mapping methods:

@Repository(forEntity = Person.class)
@MappingConfig(PersonDtoMapper.class)
public interface PersonRepository
{

    PersonDto findBySsn(String ssn);

    List<PersonDto> findByLastName(String lastName);

}

The PersonDtoMapper class has to implement the QueryInOutMapper interface:

public class PersonDtoMapper implements QueryInOutMapper<Person>
{

    @Override
    public Object mapResult(Person result)
    {
        ... // converts Person into a PersonDto
    }
    ...

    @Override
    public Object mapResultList(List<Simple> result)
    {
        ... // result lists can also be mapped into something different
            // than a collection.
    }

    @Override
    public boolean mapsParameter(Object parameter)
    {
        return parameter != null && (
                parameter instanceof PersonDto || parameter instanceof PersonId);
    }

    @Override
    public Object mapParameter(Object parameter)
    {
        ... // converts query parameters if required
    }
}

The mapper can also be used to transform query parameters. Parameters are converted before executing queries and calling repository extensions.

Note that those mapper classes are treated as CDI Beans, so it is possible to use injection in those beans (e.g. you might inject an EntityManager or other mappers). As the @MappingConfig refers to the mapper class directly, the mapper must be uniquely identifiable by its class.

It is also possible to combine mappings with the base Repository classes:

@Repository(forEntity = Person.class)
@MappingConfig(PersonDtoMapper.class)
public interface PersonRepository extends EntityRepository<PersonDto, PersonId>
{
    ...
}

In this case, the forEntity attribute in the @Repository annotation is mandatory. Also it is up to the mapper to convert parameters correctly (in this example, a conversion from a PersonDto parameter to Person entity and from PersonId to Long is necessary).

Simple Mappings

In many cases it is just required to map a DTO object back and forth. For this case, the SimpleQueryInOutMapperBase class can be subclassed, which only requires to override two methods:

public class PersonMapper extends SimpleQueryInOutMapperBase<Person, PersonDto>
{

    @Override
    protected Object getPrimaryKey(PersonDto dto)
    {
        return dto.getId();
    }

    @Override
    protected PersonDto toDto(Person entity)
    {
        ...
    }

    @Override
    protected Person toEntity(Person entity, PersonDto dto) {
        ...
        return entity;
    }
}

The first method, getPrimaryKey, identifies the primary key of an incoming DTO (this might need mapping too). If there is a primary key in the DTO, Data tries to retrieve the Entity and feed it to the toEntity method, so the entity to be mapped is attached to the persistence context. If there is no primary key, a new instance of the Entity is created. In any case, there is no need to map the primary key to the entity (it either does not exist or is already populated for an existing entity).

JPA Criteria API Support

Beside automatic query generation, the DeltaSpike Data module also provides a DSL-like API to create JPA 2 Criteria queries. It takes advantage of the JPA 2 meta model, which helps creating type safe queries.

The JPA meta model can easily be generated with an annotation processor. Hibernate or EclipseLink provide such a processor, which can be integrated into your compile and build cycle.

Note that this criteria API is not intended to replace the standard criteria API - it is rather a utility API that should make life easier on the most common cases for a custom query. The JPA criteria API’s strongest point is certainly its type safety - which comes at the cost of readability. We’re trying to provide a middle way here. A less powerful API, but still type safe and readable.

API Usage

The API is centered around the Criteria class and is targeted to provide a fluent interface to write criteria queries:

@Repository(forEntity = Person.class)
public abstract class PersonRepository implements CriteriaSupport<Person>
{

    public List<Person> findAdultFamilyMembers(String name, Integer minAge)
    {
        return criteria()
                .like(Person_.name, "%" + name + "%")
                .gtOrEq(Person_.age, minAge)
                .eq(Person_.validated, Boolean.TRUE)
                .orderDesc(Person_.age)
                .getResultList();
    }

}

Following comparators are supported by the API:

Name Description

.eq(…​, …​)

Property value must be equal to the given value

.in(…​, …​, …​, …​)

Property value must be in one of the given values.

.notEq(…​, …​)

Negates equality

.like(…​, …​)

A SQL like equivalent comparator. Use % on the value.

.notLike(…​, …​)

Negates the like value

.lt(…​, …​)

Property value must be less than the given value.

.ltOrEq(…​, …​)

Property value must be less than or equal to the given value.

.gt(…​, …​)

Property value must be greater than the given value.

.ltOrEq(…​, …​)

Property value must be greater than or equal to the given value.

.between(…​, …​, …​)

Property value must be between the two given values.

.isNull(…​)

Property must be null

.isNotNull(…​)

Property must be non-null

.isEmpty(…​)

Collection property must be empty

.isNotEmpty(…​)

Collection property must be non-empty

The query result can be modified with the following settings:

Name Description

.orderAsc(…​)

Sorts the result ascending by the given property. Note that this can be applied to several properties

.orderDesc(…​)

Sorts the result descending by the given property. Note that this can be applied to several properties

.distinct()

Sets distinct to true on the query.

Once all comparators and query options are applied, the createQuery() method is called. This creates a JPA TypedQuery object for the repository entity. If required, further processing can be applied here.

Joins

For simple cases, restricting on the repository entity only works out fine, but once the Data model gets more complicated, the query will have to consider relations to other entities. The module’s criteria API therefore supports joins as shown in the sample below:

@Repository
public abstract class PersonRepository extends AbstractEntityRepository<Person, Long>
{

    public List<Person> findByCompanyName(String companyName)
    {
        return criteria()
                .join(Person_.company,
                    where(Company.class)
                        .eq(Company_.name, companyName)
                )
                .eq(Person_.validated, Boolean.TRUE)
                .getResultList();
    }

}

Beside the inner and outer joins, also fetch joins are supported. Those are slighly simpler as seen in the next sample:

public abstract class PersonRepository extends AbstractEntityRepository<Person, Long>
{

    public Person findBySSN(String ssn)
    {
        return criteria()
                .fetch(Person_.familyMembers)
                .eq(Person_.ssn, ssn)
                .distinct()
                .getSingleResult();
    }

}

Boolean Operators

By default, all query operators are concatenated as an and conjunction to the query. The DeltaSpike criteria API also allows to add groups of disjunctions.

public abstract class PersonRepository extends AbstractEntityRepository<Person, Long>
{

    public List<Person> findAdults()
    {
        return criteria()
                .or(
                    criteria().
                        .gtOrEq(Person_.age, 18)
                        .eq(Person_.origin, Country.SWITZERLAND),
                    criteria().
                        .gtOrEq(Person_.age, 21)
                        .eq(Person_.origin, Country.USA)
                )
                .getResultList();
    }

}

Selections

It might not always be appropriate to retrieve full entities - you might also be interested in scalar values or by modified entity attributes. The Criteria interface allows this with the selection method:

public abstract class PersonRepository extends AbstractEntityRepository<Person, Long>
{

    public Statistics ageStatsFor(Segment segment)
    {
        return criteria()
                 .select(Statistics.class, avg(Person_.age), min(Person_.age), max(Person_.age))
                 .eq(Person_.segment, segment)
                 .getSingleResult();
    }

    public List<Object[]> personViewForFamily(String name)
    {
        return criteria()
                 .select(upper(Person_.name), attribute(Person_.age), substring(Person_.firstname, 1))
                 .like(Person_.name, name)
                 .getResultList();
    }

}

There are also several functions supported which can be used in the selection clause:

Name Description

abs(…​)

Absolute value. Applicable to Number attributes.

avg(…​)

Average value. Applicable to Number attributes.

count(…​)

Count function. Applicable to Number attributes.

max(…​)

Max value. Applicable to Number attributes.

min(…​)

Min value. Applicable to Number attributes.

modulo(…​)

Modulo function. Applicable to Integer attributes.

neg(…​)

Negative value. Applicable to Number attributes.

sum(…​)

Sum function. Applicable to Number attributes.

lower(…​)

String to lowercase. Applicable to String attributes.

substring(int from, …​)

Substring starting from. Applicable to String attributes.

substring(int from, int to, …​)

Substring starting from ending to. Applicable to String attributes.

upper(…​)

String to uppercase. Applicable to String attributes.

currDate()

The DB sysdate. Returns a Date object.

currTime()

The DB sysdate. Returns a Time object.

currTStamp()

The DB sysdate. Returns a Timestamp object.

Auditing

A common requirement for entities is tracking what is being done with them. DeltaSpike provides a convenient way to support this requirement.

DeltaSpike does not support creating revisions of entities. If this is a requirement for your audits, have a look at Hibernate Envers.

Activating Auditing

DeltaSpike uses an entity listener to update auditing data before entities get created or update. The entity listener must be activated before it can be used. This can either be done globally for all entities of a persistent unit or per entity.

Activation per persistence unit in orm.xml:

<entity-mappings xmlns="http://java.sun.com/xml/ns/persistence/orm"
        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
        xsi:schemaLocation="http://java.sun.com/xml/ns/persistence/orm http://java.sun.com/xml/ns/persistence/orm_2_0.xsd" version="2.0">
    <persistence-unit-metadata>
        <persistence-unit-defaults>
            <entity-listeners>
                <entity-listener class="org.apache.deltaspike.data.impl.audit.AuditEntityListener" />
            </entity-listeners>
        </persistence-unit-defaults>
    </persistence-unit-metadata>
</entity-mappings>

Activation per entity:

@Entity
@EntityListeners(AuditEntityListener.class)
public class AuditedEntity
{

    ...

}

Note that for this variant, you need a compile dependency on the impl module. Alternatively, also the per entity listener can be configured by XML.

Using Auditing Annotations

All that has to be done now is annotating the entity properties which are used to audit the entity.

Updating Timestamps

To keep track on creation and modification times, following annotations can be used:

@Entity
public class AuditedEntity
{

    ...

    @Temporal(TemporalType.TIMESTAMP)
    @CreatedOn
    private Date created;

    @Temporal(TemporalType.TIMESTAMP)
    @ModifiedOn
    private Date updated;

    ...

}

In case the modification date should also be set during entity creation, the annotation can be customized:

@ModifiedOn(setOnCreate=true)

Who’s Changing My Entities?

Beside keeping track of when a change has happened, it is also often critical to track who’s responsible for the change. Annotate a user tracking field with the following annotation:

@Entity
public class AuditedEntity
{

    ...

    @ModifiedBy
    private String auditUser;

    ...

}

Now a little help is needed. The entity listener needs to be able to resolve the current user - there must be a bean available of the matching type for the annotation property, exposed over a special CDI qualifier:

public class UserProvider
{

    @Inject
    private User user;

    @Produces @CurrentUser
    public String currentUser() {
        return user.getUsername();
    }

    ...

}
The JPA Spec does not recommend to modify entity relations from within a lifecycle callback. If you expose another entity here, make sure that your persistence provider supports this. Also you should ensure that the entity is attached to a persistent context. Also, be aware that the CDI container will proxy a scoped bean, which might confuse the persistence provider when persisting / updating the target entity.