Enhancement#373 custom identifier generator support

jopa-api/src/main/java/cz/cvut/kbss/jopa/id/IdentifierGenerator.java

@@ -0,0 +1,20 @@
+package cz.cvut.kbss.jopa.id;
+
+import cz.cvut.kbss.jopa.model.metamodel.EntityType;
+import cz.cvut.kbss.ontodriver.Connection;
+
+/**
+ * Generates identifiers for entities.
+ */
+public interface IdentifierGenerator {
+
+    /**
+     * Generate identifier for the specified entity.
+     *
+     * @param entity      Entity for which to generate the identifier
+     * @param entityClass Entity class
+     * @param connection  Storage connection
+     * @return Generated identifier
+     */
+    <T> Object generate(Object entity, EntityType<T> entityClass, Connection connection);
+}

jopa-api/src/main/java/cz/cvut/kbss/jopa/model/annotations/IdGenerator.java

@@ -0,0 +1,23 @@
+package cz.cvut.kbss.jopa.model.annotations;
+
+import cz.cvut.kbss.jopa.id.IdentifierGenerator;
+
+import java.lang.annotation.Documented;
+import java.lang.annotation.ElementType;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
+
+/**
+ * Specifies the identifier generator to use for the entity.
+ */
+@Documented
+@Target(ElementType.FIELD)
+@Retention(RetentionPolicy.RUNTIME)
+public @interface IdGenerator {
+
+    /**
+     * The identifier generator class.
+     */
+    Class<? extends IdentifierGenerator> value();
+}

jopa-impl/src/main/java/cz/cvut/kbss/jopa/id/AbstractIdentifierGenerator.java

@@ -0,0 +1,39 @@
+package cz.cvut.kbss.jopa.id;
+
+import cz.cvut.kbss.ontodriver.Connection;
+import cz.cvut.kbss.ontodriver.exception.IdentifierGenerationException;
+import cz.cvut.kbss.ontodriver.exception.OntoDriverException;
+import cz.cvut.kbss.ontodriver.model.Assertion;
+import cz.cvut.kbss.ontodriver.model.AxiomImpl;
+import cz.cvut.kbss.ontodriver.model.NamedResource;
+import cz.cvut.kbss.ontodriver.model.Value;
+
+import java.net.URI;
+import java.util.Set;
+
+/**
+ * Common superclass with utilities for identifier generation.
+ */
+public abstract class AbstractIdentifierGenerator implements IdentifierGenerator {
+
+    /**
+     * Checks if a class assertion for the specified identifier exists in the repository.
+     * <p>
+     * This check is done against the default context.
+     *
+     * @param identifier Instance identifier
+     * @param classIri   Class identifier
+     * @param connection Repository connection
+     * @return {@code true} if the class assertion exists, {@code false} otherwise
+     * @throws IdentifierGenerationException If unable to check if the identifier exists
+     */
+    protected boolean exists(URI identifier, URI classIri, Connection connection) {
+        try {
+            return connection.contains(new AxiomImpl<>(NamedResource.create(identifier),
+                    Assertion.createClassAssertion(false),
+                    new Value<>(classIri)), Set.of());
+        } catch (OntoDriverException e) {
+            throw new IdentifierGenerationException("Unable to check if identifier '" + identifier + "' exists.", e);
+        }
+    }
+}

jopa-impl/src/main/java/cz/cvut/kbss/jopa/id/RandomNumberIdentifierGenerator.java

@@ -0,0 +1,46 @@
+package cz.cvut.kbss.jopa.id;
+
+import cz.cvut.kbss.jopa.model.metamodel.EntityType;
+import cz.cvut.kbss.ontodriver.Connection;
+import cz.cvut.kbss.ontodriver.exception.IdentifierGenerationException;
+
+import java.net.URI;
+import java.util.Objects;
+import java.util.Random;
+
+public class RandomNumberIdentifierGenerator extends AbstractIdentifierGenerator {
+
+    private static final int GENERATION_THRESHOLD = 64;
+
+    private static final Random RANDOM = new Random();
+
+    @Override
+    public <T> URI generate(Object entity, EntityType<T> entityClass, Connection connection) {
+        Objects.requireNonNull(entity);
+        Objects.requireNonNull(entityClass);
+        Objects.requireNonNull(connection);
+
+        final URI classUri = entityClass.getIRI().toURI();
+        int counter = 0;
+        while (counter++ < GENERATION_THRESHOLD) {
+            final URI id = generate(classUri);
+            if (!exists(id, classUri, connection)) {
+                return id;
+            }
+        }
+        throw new IdentifierGenerationException("Unable to generate a unique identifier.");
+    }
+
+    private URI generate(URI classUri) {
+        if (classUri.getFragment() != null) {
+            return URI.create(classUri + "_instance" + RANDOM.nextInt());
+        } else {
+            String base = classUri.toString();
+            if (base.endsWith("/")) {
+                return URI.create(base + "instance" + RANDOM.nextInt());
+            } else {
+                return URI.create(base + "/instance" + RANDOM.nextInt());
+            }
+        }
+    }
+}

jopa-impl/src/main/java/cz/cvut/kbss/jopa/model/MetamodelImpl.java

@@ -18,6 +18,8 @@
 package cz.cvut.kbss.jopa.model;
 
 import cz.cvut.kbss.jopa.exceptions.OWLPersistenceException;
+import cz.cvut.kbss.jopa.id.IdentifierGenerator;
+import cz.cvut.kbss.jopa.id.RandomNumberIdentifierGenerator;
 import cz.cvut.kbss.jopa.loaders.PersistenceUnitClassFinder;
 import cz.cvut.kbss.jopa.model.metamodel.EntityType;
 import cz.cvut.kbss.jopa.model.metamodel.IdentifiableEntityType;
@@ -61,6 +63,8 @@ public class MetamodelImpl implements Metamodel, MetamodelProvider, MetamodelCla
     // Proxy classes for results of EntityManager.getReference
     private final Map<Class<?>, Class<?>> referenceProxyClasses = new ConcurrentHashMap<>();
 
+    private Map<EntityType<?>, IdentifierGenerator> idGenerators;
+
     private NamedQueryManager namedQueryManager;
     private ResultSetMappingManager resultSetMappingManager;
     private NamedEntityGraphManager namedEntityGraphManager;
@@ -108,6 +112,7 @@ private void initFromMetamodelBuilder(MetamodelBuilder metamodelBuilder) {
         this.namespaceResolver = metamodelBuilder.getNamespaceResolver();
         this.typeReferenceMap = metamodelBuilder.getTypeReferenceMap();
         this.lazyLoadingProxyClasses.putAll(metamodelBuilder.getLazyLoadingEntityProxyClasses());
+        this.idGenerators = metamodelBuilder.getIdGenerators();
     }
 
     /**
@@ -176,6 +181,10 @@ public NamedEntityGraphManager getNamedEntityGraphManager() {
         return namedEntityGraphManager;
     }
 
+    public IdentifierGenerator getIdentifierGenerator(EntityType<?> entityType) {
+        return idGenerators.getOrDefault(entityType, new RandomNumberIdentifierGenerator());
+    }
+
     @Override
     public Set<URI> getModuleExtractionExtraSignature() {
         return Collections.unmodifiableSet(getSignatureInternal());

jopa-impl/src/main/java/cz/cvut/kbss/jopa/model/metamodel/MetamodelBuilder.java

@@ -18,11 +18,13 @@
 package cz.cvut.kbss.jopa.model.metamodel;
 
 import cz.cvut.kbss.jopa.exception.MetamodelInitializationException;
+import cz.cvut.kbss.jopa.id.IdentifierGenerator;
 import cz.cvut.kbss.jopa.loaders.PersistenceUnitClassFinder;
 import cz.cvut.kbss.jopa.model.JOPAPersistenceProperties;
 import cz.cvut.kbss.jopa.model.NamedEntityGraphManager;
 import cz.cvut.kbss.jopa.model.NamedEntityGraphProcessor;
 import cz.cvut.kbss.jopa.model.TypeReferenceMap;
+import cz.cvut.kbss.jopa.model.annotations.IdGenerator;
 import cz.cvut.kbss.jopa.model.annotations.Inheritance;
 import cz.cvut.kbss.jopa.model.annotations.InheritanceType;
 import cz.cvut.kbss.jopa.model.annotations.OWLAnnotationProperty;
@@ -38,7 +40,9 @@
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
+import java.lang.reflect.Constructor;
 import java.lang.reflect.Field;
+import java.lang.reflect.InvocationTargetException;
 import java.lang.reflect.Method;
 import java.util.ArrayList;
 import java.util.Arrays;
@@ -333,6 +337,32 @@ public Map<Class<?>, Class<?>> getLazyLoadingEntityProxyClasses() {
         return Collections.unmodifiableMap(lazyLoadingProxyClasses);
     }
 
+    public Map<EntityType<?>, IdentifierGenerator> getIdGenerators() {
+        final Map<Class<? extends IdentifierGenerator>, IdentifierGenerator> generators = new HashMap<>();
+        final Map<EntityType<?>, IdentifierGenerator> result = new HashMap<>();
+        for (EntityType<?> et : getEntities().values()) {
+            if (et.getJavaType().isInterface() || !et.getIdentifier().isGenerated()) {
+                continue;
+            }
+            final IdGenerator idGeneratorAnn = et.getIdentifier().getJavaField().getAnnotation(IdGenerator.class);
+            if (idGeneratorAnn == null) {
+                continue;
+            }
+            final IdentifierGenerator gen = generators.computeIfAbsent(idGeneratorAnn.value(), cls -> {
+                try {
+                    final Constructor<? extends IdentifierGenerator> constructor = cls.getDeclaredConstructor();
+                    return constructor.newInstance();
+                } catch (NoSuchMethodException | SecurityException e) {
+                    throw new MetamodelInitializationException("Custom identifier generator class " + cls + " is missing public no-arg constructor.");
+                } catch (InvocationTargetException | InstantiationException | IllegalAccessException e) {
+                    throw new MetamodelInitializationException("Failed to create instance of custom identifier generator " + cls, e);
+                }
+            });
+            result.put(et, gen);
+        }
+        return result;
+    }
+
     public Set<AnnotatedAccessor> getAnnotatedAccessorsForClass(IdentifiableType<?> k) {
         return annotatedAccessors.getOrDefault(k, Collections.emptySet());
     }

jopa-impl/src/main/java/cz/cvut/kbss/jopa/oom/EntityMappingHelper.java

@@ -35,7 +35,7 @@ interface EntityMappingHelper extends ConfigurationHolder {
 
     <T> EntityType<T> getEntityType(Class<T> cls);
 
-    URI generateIdentifier(EntityType<?> et);
+    Object generateIdentifier(Object entity, EntityType<?> et);
 
     <T> T getOriginalInstance(T clone);
 

jopa-impl/src/main/java/cz/cvut/kbss/jopa/oom/FieldStrategy.java

@@ -224,12 +224,12 @@ Object extractFieldValueFromInstance(Object instance) {
     }
 
     <E> URI resolveValueIdentifier(E instance, EntityType<E> valEt) {
-        URI id = EntityPropertiesUtils.getIdentifier(instance, valEt);
+        Object id = EntityPropertiesUtils.getIdentifier(instance, valEt);
         if (id == null) {
-            id = mapper.generateIdentifier(valEt);
+            id = mapper.generateIdentifier(instance, valEt);
             EntityPropertiesUtils.setIdentifier(id, instance, valEt);
         }
-        return id;
+        return id instanceof URI uri ? uri : URI.create(id.toString());
     }
 
     /**

jopa-impl/src/main/java/cz/cvut/kbss/jopa/oom/ObjectOntologyMapper.java

@@ -18,7 +18,6 @@
 package cz.cvut.kbss.jopa.oom;
 
 import cz.cvut.kbss.jopa.model.descriptors.Descriptor;
-import cz.cvut.kbss.jopa.model.metamodel.EntityType;
 import cz.cvut.kbss.jopa.model.metamodel.FieldSpecification;
 import cz.cvut.kbss.jopa.oom.exception.UnpersistedChangeException;
 import cz.cvut.kbss.jopa.sessions.util.AxiomBasedLoadingParameters;
@@ -81,14 +80,6 @@ public interface ObjectOntologyMapper {
      */
     <T> void loadFieldValue(T entity, FieldSpecification<? super T, ?> fieldSpec, Descriptor descriptor);
 
-    /**
-     * Generates a fresh identifier for an instance of the specified entity type.
-     *
-     * @param et Entity type used as base for the identifier
-     * @return New entity identifier
-     */
-    URI generateIdentifier(EntityType<?> et);
-
     /**
      * Persists the specified entity into the underlying ontology.
      *

jopa-impl/src/main/java/cz/cvut/kbss/jopa/oom/ObjectOntologyMapperImpl.java

@@ -252,12 +252,8 @@ public <T> void persistEntity(URI identifier, T entity, Descriptor descriptor) {
     }
 
     @Override
-    public URI generateIdentifier(EntityType<?> et) {
-        try {
-            return storageConnection.generateIdentifier(et.getIRI().toURI());
-        } catch (OntoDriverException e) {
-            throw new StorageAccessException(e);
-        }
+    public Object generateIdentifier(Object entity, EntityType<?> et) {
+        return uow.getMetamodel().getIdentifierGenerator(et).generate(entity, et, storageConnection);
     }
 
     private <T> void persistPendingReferences(T instance, NamedResource identifier) {
@@ -293,23 +289,25 @@ public <T> T getEntityFromCacheOrOntology(Class<T> cls, URI identifier, ObjectGr
         if (orig != null) {
             return orig;
         }
-        return defaultInstanceLoader.loadCached(getEntityType(cls), identifier, objectGraphInfo.descriptor()).orElseGet(() -> {
-            if (instanceRegistry.containsKey(identifier)) {
-                final Object existing = instanceRegistry.get(identifier);
-                if (!cls.isAssignableFrom(existing.getClass())) {
-                    throw individualAlreadyManaged(identifier);
-                }
-                // This prevents endless cycles in bidirectional relationships
-                return cls.cast(existing);
-            } else {
-                // setup loading params
-                LoadingParameters<T> params = initEntityLoadingParameters(cls, identifier, objectGraphInfo);
-                return axiomsPerEntity.containsKey(identifier) ? loadEntityFromAxioms(params) : loadEntityInternal(params);
-            }
-        });
-    }
-
-    private <T> LoadingParameters<T> initEntityLoadingParameters(Class<T> cls, URI identifier, ObjectGraphInfo objectGraphInfo) {
+        return defaultInstanceLoader.loadCached(getEntityType(cls), identifier, objectGraphInfo.descriptor())
+                                    .orElseGet(() -> {
+                                        if (instanceRegistry.containsKey(identifier)) {
+                                            final Object existing = instanceRegistry.get(identifier);
+                                            if (!cls.isAssignableFrom(existing.getClass())) {
+                                                throw individualAlreadyManaged(identifier);
+                                            }
+                                            // This prevents endless cycles in bidirectional relationships
+                                            return cls.cast(existing);
+                                        } else {
+                                            // setup loading params
+                                            LoadingParameters<T> params = initEntityLoadingParameters(cls, identifier, objectGraphInfo);
+                                            return axiomsPerEntity.containsKey(identifier) ? loadEntityFromAxioms(params) : loadEntityInternal(params);
+                                        }
+                                    });
+    }
+
+    private <T> LoadingParameters<T> initEntityLoadingParameters(Class<T> cls, URI identifier,
+                                                                 ObjectGraphInfo objectGraphInfo) {
         return new LoadingParameters<>(cls, identifier, objectGraphInfo.descriptor(), objectGraphInfo.fetchGraph(), false, uow.isReadOnly());
     }
 

jopa-impl/src/main/java/cz/cvut/kbss/jopa/sessions/AbstractUnitOfWork.java

@@ -738,7 +738,7 @@ private Object initEntityIdentifier(Object entity, EntityType<Object> et) {
         Object id = getIdentifier(entity);
         if (id == null) {
             EntityPropertiesUtils.verifyIdentifierIsGenerated(entity, et);
-            id = storage.generateIdentifier(et);
+            id = getMetamodel().getIdentifierGenerator(et).generate(entity, et, storage.getConnection());
             EntityPropertiesUtils.setIdentifier(id, entity, et);
         }
         return id;

jopa-impl/src/main/java/cz/cvut/kbss/jopa/sessions/ConnectionWrapper.java

@@ -19,7 +19,6 @@
 
 import cz.cvut.kbss.jopa.exceptions.OWLPersistenceException;
 import cz.cvut.kbss.jopa.model.descriptors.Descriptor;
-import cz.cvut.kbss.jopa.model.metamodel.EntityType;
 import cz.cvut.kbss.jopa.model.metamodel.FieldSpecification;
 import cz.cvut.kbss.jopa.oom.ObjectOntologyMapper;
 import cz.cvut.kbss.jopa.oom.ObjectOntologyMapperImpl;
@@ -76,10 +75,6 @@ public <T> void merge(T entity, FieldSpecification<? super T, ?> fieldSpec, Desc
         mapper.updateFieldValue(entity, fieldSpec, descriptor);
     }
 
-    public URI generateIdentifier(EntityType<?> et) {
-        return mapper.generateIdentifier(et);
-    }
-
     public <T> void persist(Object identifier, T entity, Descriptor descriptor) {
         final URI idUri = getIdentifierAsUri(identifier);
         mapper.persistEntity(idUri, entity, descriptor);
@@ -165,6 +160,10 @@ public RepositoryMetadata getRepositoryMetadata() {
         return connection.getRepositoryMetadata();
     }
 
+    public Connection getConnection() {
+        return connection;
+    }
+
     @Override
     public <T> T unwrap(Class<T> cls) {
         try {

jopa-impl/src/test/java/cz/cvut/kbss/jopa/accessors/DataSourceStub.java

@@ -142,11 +142,6 @@ public Collection<Axiom<?>> find(AxiomDescriptor descriptor) {
         @Override
         public void persist(AxiomValueDescriptor descriptor) {}
 
-        @Override
-        public URI generateIdentifier(URI classUri) {
-            return null;
-        }
-
         @Override
         public void update(AxiomValueDescriptor descriptor) {}