NameBuilding.adoc

How to get own names for the OData artifacts?

The JPA Processor generates out of the JPA annotations or metadata the corresponding OData metadata. This includes also the generation of the names. By default e.g. all OData artifacts start with an upper case character and entity sets are in plural. There are multiple reasons to have another naming. E.g. different naming conventions, like properties shall be in lower case, or a noun used as entity name has no plural.

Our service has an entity set Persons, which shall be named People instead.

The names of the artifacts are created by a class implementing interface JPAEdmNameBuilder. As mentioned, for our service, we just want to override Persons. For the rest we take the default names.

As a first step we create an implementation of JPAEdmNameBuilder called APINameBuilder. It creates an instance of JPADefaultEdmNameBuilder to fallback to the default names and returns People as entity set name for entity type Person:

import javax.persistence.metamodel.Attribute;
import javax.persistence.metamodel.EmbeddableType;
import javax.persistence.metamodel.EntityType;

import com.sap.olingo.jpa.metadata.core.edm.mapper.api.JPAEdmNameBuilder;
import com.sap.olingo.jpa.metadata.core.edm.mapper.impl.JPADefaultEdmNameBuilder;

class APINameBuilder implements JPAEdmNameBuilder {
  private final JPAEdmNameBuilder defaultNameBuilder;

  APINameBuilder(final String punit) {
    defaultNameBuilder = new JPADefaultEdmNameBuilder(punit); //(1)
  }

  @Override
  public String buildComplexTypeName(final EmbeddableType<?> jpaEmbeddedType) {
    return defaultNameBuilder.buildComplexTypeName(jpaEmbeddedType);
  }

  @Override
  public String buildContainerName() {
    return defaultNameBuilder.buildContainerName();
  }

  @Override
  public String buildEntitySetName(final String entityTypeName) {
    return "Person".equals(entityTypeName) ? "People" : defaultNameBuilder.buildEntitySetName(entityTypeName); //(2)
  }

  @Override
  public String buildEntityTypeName(final EntityType<?> jpaEntityType) {
    return defaultNameBuilder.buildEntityTypeName(jpaEntityType);
  }

  @Override
  public String buildEnumerationTypeName(final Class<? extends Enum<?>> javaEnum) {
    return defaultNameBuilder.buildEnumerationTypeName(javaEnum);
  }

  @Override
  public String buildNaviPropertyName(final Attribute<?, ?> jpaAttribute) {
    return defaultNameBuilder.buildNaviPropertyName(jpaAttribute);
  }

  @Override
  public String buildOperationName(final String internalOperationName) {
    return defaultNameBuilder.buildOperationName(internalOperationName);
  }

  @Override
  public String buildPropertyName(final String jpaAttributeName) {
    return defaultNameBuilder.buildPropertyName(jpaAttributeName);
  }

  @Override
  public String getNamespace() {
    return defaultNameBuilder.getNamespace();
  }
}

1. Create an instance of the default name builder.

2. Override the name of the entity set for person.

The second step is to hand over the name builder to the session context. The session context is created in class ProcessorConfiguration by method sessionContext. We add .setEdmNameBuilder(new APINameBuilder(punit)):

  @Bean
  public JPAODataSessionContextAccess sessionContext(@Autowired final EntityManagerFactory emf) throws ODataException {

    return JPAODataServiceContext.with()
        .setPUnit(punit)
        .setEntityManagerFactory(emf)
        .setTypePackage(rootPackages)
        .setRequestMappingPath("Trippin/v1")
        .setEdmNameBuilder(new APINameBuilder(punit)) //(1)
        .build();
  }

1. Provide the name builder to the session context.

Starting the service and executing http://localhost:9010/Trippin/v1/$metadata will return:

...
<EntityContainer Name="TrippinContainer">
  <EntitySet Name="People" EntityType="Trippin.Person">
    <NavigationPropertyBinding Path="Trips" Target="Trips"/>
  </EntitySet>
  <EntitySet Name="Trips" EntityType="Trippin.Trip"/>
</EntityContainer>
...