Add support for Named Query in JpaPagingItemReader

Issue #1667

spring-batch-infrastructure/src/main/java/org/springframework/batch/item/database/orm/JpaNamedQueryProvider.java

@@ -0,0 +1,64 @@
+/*
+ * Copyright 2020 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
+ * @author Parikshit Dutta
+ * @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);
+	}
+
+	/**
+	 * @param namedQuery name of a jpa named query
+	 */
+	public void setNamedQuery(String namedQuery) {
+		this.namedQuery = namedQuery;
+	}
+
+	/**
+	 * @param entityClazz name of a jpa entity class
+	 */
+	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");
+	}
+}