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GEARS Runtime Common
There is a newer version: 1.17.5
package com.xlrit.gears.base.repository;

import java.util.List;
import jakarta.persistence.EntityManager;
import jakarta.persistence.PersistenceContext;
import jakarta.persistence.TypedQuery;
import jakarta.persistence.criteria.CriteriaBuilder;
import jakarta.persistence.criteria.CriteriaQuery;
import jakarta.persistence.criteria.Root;

import com.xlrit.gears.base.execution.Execution;
import com.xlrit.gears.base.id.IdGenerator;

import org.hibernate.metamodel.spi.MetamodelImplementor;
import org.hibernate.persister.entity.SingleTableEntityPersister;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.data.jpa.domain.Specification;

public abstract class JpaRepository extends AbstractRepository {
	private static final Logger LOG = LoggerFactory.getLogger(JpaRepository.class);

	@PersistenceContext
	protected EntityManager em;

	@Autowired
	protected IdGenerator idGenerator;

	protected JpaRepository(Class entityType) {
		super(entityType);
	}

	public TypedQuery query(String qlString) {
		return em.createQuery(qlString, entityType);
	}

	public  TypedQuery query(Class resultType, String qlString) {
		return em.createQuery(qlString, resultType);
	}

	public interface CriteriaQueryHandler {
		void apply(CriteriaBuilder criteriaBuilder, CriteriaQuery query);
	}

	public TypedQuery query(CriteriaQueryHandler handler) {
		CriteriaBuilder criteriaBuilder = em.getCriteriaBuilder();
		CriteriaQuery query = criteriaBuilder.createQuery(entityType);
		handler.apply(criteriaBuilder, query);
		return em.createQuery(query);
	}

	public  TypedQuery query(Class resultClass, CriteriaQueryHandler f) {
		CriteriaBuilder criteriaBuilder = em.getCriteriaBuilder();
		CriteriaQuery query = criteriaBuilder.createQuery(resultClass);
		f.apply(criteriaBuilder, query);
		return em.createQuery(query);
	}

	@Override
	public T findById(String id) {
		return em.find(entityType, id);
	}

	@Override
	public List findAll() {
		return em.createQuery("SELECT o FROM " + entityType.getName() + " o", entityType).getResultList();
	}

	@Override
	public List findMany(Specification spec) {
		query((cb, q) -> {
			Root root = q.from(entityType);
			if (spec != null) q.where(spec.toPredicate(root, q, cb));
		}).getResultList();
		CriteriaBuilder criteriaBuilder = em.getCriteriaBuilder();
		CriteriaQuery query = criteriaBuilder.createQuery(entityType);
		Root root = query.from(entityType);
		if (spec != null) query.where(spec.toPredicate(root, query, criteriaBuilder));
		return em.createQuery(query).getResultList();
	}

	@Override
	protected T doCreate(Execution execution) {
		T instance = newInstance(idGenerator.getNextId());
		em.persist(instance);
		return instance;
	}

	@Override
	protected void doRemove(T instance, Execution execution) {
		em.remove(instance);
	}

	public String getTableName() {
		if (em.getMetamodel() instanceof MetamodelImplementor metamodel
			&& metamodel.entityPersister(entityType) instanceof SingleTableEntityPersister entityPersister) {
			return entityPersister.getTableName();
		}
		return null;
	}

	public List getColumnNames(List fieldNames) {
		try {
			if (em.getMetamodel() instanceof MetamodelImplementor metamodel
				&& metamodel.entityPersister(entityType) instanceof SingleTableEntityPersister entityPersister) {
				return fieldNames.stream()
					.map(fieldName -> {
						String[] columnNames = entityPersister.getPropertyColumnNames(fieldName);
						if (columnNames.length != 1) throw new RuntimeException("Expected field '" + fieldName + "' to be mapped to exactly one column: " + columnNames);
						return columnNames[0];
					})
					.toList();
			}
		}
		catch (RuntimeException e) {
			LOG.debug("Unable to map one or more field names to column names: {}", fieldNames);
		}
		return null;
	}
}