Add support for named queries in JpaPagingItemReader

[spring-projects-issues]

David Zeigler opened BATCH-1926 and commented

The Hibernate ItemReaders support queryName as an alternative to queryString allowing the reader to use a named query.

JpaPagingItemReader needs to support this option as well. When queryName is set, the javax.persistence.Query should be created using entityManager.createNamedQuery(queryName);

---

Affects: 2.1.9

[spring-projects-issues]

Mahmoud Ben Hassine commented

It is possible to use a namedQuery by providing a custom JpaQueryProvider. Similar to the JpaNativeQueryProvider for native queries, you can create a JpaNamedQueryProvider for named queries. Or using an inner class for example:

JpaPagingItemReader<Foo> reader = new JpaPagingItemReaderBuilder<Foo>()
		.name("fooReader")
		.queryProvider(new AbstractJpaQueryProvider() {
			@Override
			public Query createQuery() {
				return getEntityManager().createNamedQuery("your named query");
			}

			@Override
			public void afterPropertiesSet() throws Exception {

			}
		})
		// set other properties on the reader
		.build();

So support for named queries on JpaPagingItemReader is already provided through the JpaQueryProvider API.

@David Zeigler Do you agree?

[spring-projects-issues]

Mahmoud Ben Hassine commented

After re-reading this issue, I believe Spring Batch can provide the class to free the user from doing it as in my previous comment. The new JpaNamedQueryProvider could look like this (inspired by JpaNativeQueryProvider):

/*
 * Copyright 2019 the original author or authors.
 *
 * 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
 *
 *      https://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 org.springframework.batch.item.database.orm;

import javax.persistence.Query;

import org.springframework.util.Assert;
import org.springframework.util.StringUtils;

/**
 * <p>
 * This query provider creates JPA named {@link Query}s.
 * </p>
 * 
 * @author Mahmoud Ben Hassine
 * @since 4.3
 * 
 * @param <E> entity returned by executing the query
 */
public class JpaNamedQueryProvider<E> extends AbstractJpaQueryProvider {

	private Class<E> entityClass;

	private String namedQuery;

    @Override
	public Query createQuery() {
		return getEntityManager().createNamedQuery(namedQuery, entityClass);
	}

	public void setNamedQuery(String namedQuery) {
		this.namedQuery = namedQuery;
	}

	public void setEntityClass(Class<E> entityClazz) {
		this.entityClass = entityClazz;
	}

    @Override
	public void afterPropertiesSet() throws Exception {
		Assert.isTrue(StringUtils.hasText(namedQuery), "Named query cannot be empty");
		Assert.notNull(entityClass, "Entity class cannot be NULL");
	}
}

I will open a PR with corresponding test (contributions are welcome).

[parikshitdutta]

Hi @benas, would you like to assign this to me?

Thank you.

[parikshitdutta]

Hi @benas, as you find time, please review the PR #3726. I will look forward to your feedback.

Thank you.

[fmbenhassine]

Resolved with #3726 .