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JPA support for Querydsl
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/*
 * Copyright 2015, The Querydsl Team (http://www.querydsl.com/team)
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 * http://www.apache.org/licenses/LICENSE-2.0
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package com.querydsl.jpa;

import com.mysema.commons.lang.CloseableIterator;
import com.mysema.commons.lang.IteratorAdapter;
import com.querydsl.core.types.FactoryExpression;
import jakarta.persistence.PersistenceException;
import jakarta.persistence.Query;
import java.util.Iterator;
import java.util.List;
import java.util.stream.Stream;
import org.hibernate.query.NativeQuery;
import org.hibernate.transform.ResultTransformer;
import org.jetbrains.annotations.Nullable;

/**
 * {@code HibernateHandler} is the {@link QueryHandler} implementation for Hibernate
 *
 * @author tiwe
 */
public class HibernateHandler implements QueryHandler {

  @Override
  public void addEntity(Query query, String alias, Class type) {
    query.unwrap(NativeQuery.class).addEntity(alias, type);
  }

  @Override
  public void addScalar(Query query, String alias, Class type) {
    query.unwrap(NativeQuery.class).addScalar(alias);
  }

  @Override
  public boolean createNativeQueryTyped() {
    return false;
  }

  @SuppressWarnings("unchecked")
  @Override
  public  CloseableIterator iterate(Query query, FactoryExpression projection) {
    try {
      org.hibernate.query.Query unwrappedQuery = query.unwrap(org.hibernate.query.Query.class);
      CloseableIterator iterator =
          new ScrollableResultsIterator<>((List) unwrappedQuery.getResultList());
      if (projection != null) {
        iterator = new TransformingIterator<>(iterator, projection);
      }
      return iterator;
    } catch (PersistenceException e) {
      Iterator iterator = query.getResultList().iterator();
      if (projection != null) {
        return new TransformingIterator<>(iterator, projection);
      } else {
        return new IteratorAdapter<>(iterator);
      }
    }
  }

  @Override
  @SuppressWarnings({"unchecked", "rawtypes"})
  public  Stream stream(Query query, @Nullable FactoryExpression projection) {
    final var resultStream = query.getResultStream();
    if (projection != null) {
      return resultStream.map(
          element ->
              projection.newInstance(
                  (Object[]) (element.getClass().isArray() ? element : new Object[] {element})));
    }
    return resultStream;
  }

  @Override
  public boolean transform(Query query, FactoryExpression projection) {
    try {
      ResultTransformer transformer = new FactoryExpressionTransformer(projection);
      query.unwrap(org.hibernate.query.Query.class).setResultTransformer(transformer);
      return true;
    } catch (PersistenceException e) {
      return false;
    }
  }

  @Override
  public boolean wrapEntityProjections() {
    return true;
  }
}