Add JpaCursorItemReader implementation

Issue #901
2020-09-10 13:36:34 +02:00
parent d87588c950
commit 41854008e8
4 changed files with 654 additions and 0 deletions
--- a/spring-batch-infrastructure/src/main/java/org/springframework/batch/item/database/JpaCursorItemReader.java
+++ b/spring-batch-infrastructure/src/main/java/org/springframework/batch/item/database/JpaCursorItemReader.java
@@ -0,0 +1,153 @@
+/*
+ * 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;
+
+import java.util.Iterator;
+import java.util.Map;
+
+import javax.persistence.EntityManager;
+import javax.persistence.EntityManagerFactory;
+import javax.persistence.Query;
+
+import org.springframework.batch.item.ExecutionContext;
+import org.springframework.batch.item.ItemStreamException;
+import org.springframework.batch.item.database.orm.JpaQueryProvider;
+import org.springframework.batch.item.support.AbstractItemCountingItemStreamItemReader;
+import org.springframework.beans.factory.InitializingBean;
+import org.springframework.dao.DataAccessResourceFailureException;
+import org.springframework.util.Assert;
+import org.springframework.util.ClassUtils;
+
+/**
+ * {@link org.springframework.batch.item.ItemStreamReader} implementation based
+ *  on JPA {@link Query#getResultStream()}. It executes the JPQL query when
+ *  initialized and iterates over the result set as {@link #read()} method is called,
+ *  returning an object corresponding to the current row. The query can be set
+ *  directly using {@link #setQueryString(String)}, or using a query provider via
+ *  {@link #setQueryProvider(JpaQueryProvider)}.
+ * 
+ * The implementation is <b>not</b> thread-safe.
+ * 
+ * @author Mahmoud Ben Hassine
+ * @param <T> type of items to read
+ * @since 4.3
+ */
+public class JpaCursorItemReader<T> extends AbstractItemCountingItemStreamItemReader<T>
+		implements InitializingBean {
+
+	private EntityManagerFactory entityManagerFactory;
+	private EntityManager entityManager;
+	private String queryString;
+	private JpaQueryProvider queryProvider;
+	private Map<String, Object> parameterValues;
+	private Iterator<T> iterator;
+
+	/**
+	 * Create a new {@link JpaCursorItemReader}.
+	 */
+	public JpaCursorItemReader() {
+		setName(ClassUtils.getShortName(JpaCursorItemReader.class));
+	}
+
+	/**
+	 * Set the JPA entity manager factory.
+	 *
+	 * @param entityManagerFactory JPA entity manager factory
+	 */
+	public void setEntityManagerFactory(EntityManagerFactory entityManagerFactory) {
+		this.entityManagerFactory = entityManagerFactory;
+	}
+
+	/**
+	 * Set the JPA query provider.
+	 *
+	 * @param queryProvider JPA query provider
+	 */
+	public void setQueryProvider(JpaQueryProvider queryProvider) {
+		this.queryProvider = queryProvider;
+	}
+
+	/**
+	 * Set the JPQL query string.
+	 *
+	 * @param queryString JPQL query string
+	 */
+	public void setQueryString(String queryString) {
+		this.queryString = queryString;
+	}
+
+	/**
+	 * Set the parameter values to be used for the query execution.
+	 *
+	 * @param parameterValues the values keyed by parameter names used in
+	 * the query string.
+	 */
+	public void setParameterValues(Map<String, Object> parameterValues) {
+		this.parameterValues = parameterValues;
+	}
+
+	@Override
+	public void afterPropertiesSet() throws Exception {
+		Assert.notNull(this.entityManagerFactory, "EntityManagerFactory is required");
+		if (this.queryProvider == null) {
+			Assert.hasLength(this.queryString, "Query string is required when queryProvider is null");
+		}
+	}
+
+	@Override
+	@SuppressWarnings("unchecked")
+	protected void doOpen() throws Exception {
+		this.entityManager = this.entityManagerFactory.createEntityManager();
+		if (this.entityManager == null) {
+			throw new DataAccessResourceFailureException("Unable to create an EntityManager");
+		}
+		if (this.queryProvider != null) {
+			this.queryProvider.setEntityManager(this.entityManager);
+		}
+		Query query = createQuery();
+		if (this.parameterValues != null) {
+			this.parameterValues.forEach(query::setParameter);
+		}
+		this.iterator = query.getResultStream().iterator();
+	}
+
+	private Query createQuery() {
+		if (this.queryProvider == null) {
+			return this.entityManager.createQuery(this.queryString);
+		}
+		else {
+			return this.queryProvider.createQuery();
+		}
+	}
+
+	@Override
+	protected T doRead() {
+		return this.iterator.hasNext() ? this.iterator.next() : null;
+	}
+
+	@Override
+	public void update(ExecutionContext executionContext) throws ItemStreamException {
+		super.update(executionContext);
+		this.entityManager.clear();
+	}
+
+	@Override
+	protected void doClose() {
+		if (this.entityManager != null) {
+			this.entityManager.close();
+		}
+	}
+}
--- a/spring-batch-infrastructure/src/main/java/org/springframework/batch/item/database/builder/JpaCursorItemReaderBuilder.java
+++ b/spring-batch-infrastructure/src/main/java/org/springframework/batch/item/database/builder/JpaCursorItemReaderBuilder.java
@@ -0,0 +1,182 @@
+/*
+ * 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.builder;
+
+import java.util.Map;
+
+import javax.persistence.EntityManagerFactory;
+
+import org.springframework.batch.item.ExecutionContext;
+import org.springframework.batch.item.ItemStreamSupport;
+import org.springframework.batch.item.database.JpaCursorItemReader;
+import org.springframework.batch.item.database.orm.JpaQueryProvider;
+import org.springframework.batch.item.support.AbstractItemCountingItemStreamItemReader;
+import org.springframework.util.Assert;
+
+/**
+ * Builder for {@link JpaCursorItemReader}.
+ *
+ * @author Mahmoud Ben Hassine
+ *
+ * @since 4.3
+ */
+public class JpaCursorItemReaderBuilder<T> {
+
+	private EntityManagerFactory entityManagerFactory;
+	private String queryString;
+	private JpaQueryProvider queryProvider;
+	private Map<String, Object> parameterValues;
+	private boolean saveState = true;
+	private String name;
+	private int maxItemCount = Integer.MAX_VALUE;
+	private int currentItemCount;
+
+	/**
+	 * Configure if the state of the {@link ItemStreamSupport}
+	 * should be persisted within the {@link ExecutionContext}
+	 * for restart purposes.
+	 *
+	 * @param saveState defaults to true
+	 * @return The current instance of the builder.
+	 */
+	public JpaCursorItemReaderBuilder<T> saveState(boolean saveState) {
+		this.saveState = saveState;
+
+		return this;
+	}
+
+	/**
+	 * The name used to calculate the key within the {@link ExecutionContext}.
+	 * Required if {@link #saveState(boolean)} is set to true.
+	 *
+	 * @param name name of the reader instance
+	 * @return The current instance of the builder.
+	 * @see ItemStreamSupport#setName(String)
+	 */
+	public JpaCursorItemReaderBuilder<T> name(String name) {
+		this.name = name;
+
+		return this;
+	}
+
+	/**
+	 * Configure the max number of items to be read.
+	 *
+	 * @param maxItemCount the max items to be read
+	 * @return The current instance of the builder.
+	 * @see AbstractItemCountingItemStreamItemReader#setMaxItemCount(int)
+	 */
+	public JpaCursorItemReaderBuilder<T> maxItemCount(int maxItemCount) {
+		this.maxItemCount = maxItemCount;
+
+		return this;
+	}
+
+	/**
+	 * Index for the current item. Used on restarts to indicate where to start from.
+	 *
+	 * @param currentItemCount current index
+	 * @return this instance for method chaining
+	 * @see AbstractItemCountingItemStreamItemReader#setCurrentItemCount(int)
+	 */
+	public JpaCursorItemReaderBuilder<T> currentItemCount(int currentItemCount) {
+		this.currentItemCount = currentItemCount;
+
+		return this;
+	}
+
+	/**
+	 * A map of parameter values to be set on the query. The key of the map is 
+	 * the name of the parameter to be set with the value being the value to be set.
+	 *
+	 * @param parameterValues map of values
+	 * @return this instance for method chaining
+	 * @see JpaCursorItemReader#setParameterValues(Map)
+	 */
+	public JpaCursorItemReaderBuilder<T> parameterValues(Map<String, Object> parameterValues) {
+		this.parameterValues = parameterValues;
+
+		return this;
+	}
+
+	/**
+	 * A query provider. This should be set only if {@link #queryString(String)}
+	 * have not been set.
+	 *
+	 * @param queryProvider the query provider
+	 * @return this instance for method chaining
+	 * @see JpaCursorItemReader#setQueryProvider(JpaQueryProvider)
+	 */
+	public JpaCursorItemReaderBuilder<T> queryProvider(JpaQueryProvider queryProvider) {
+		this.queryProvider = queryProvider;
+
+		return this;
+	}
+
+	/**
+	 * The JPQL query string to execute. This should only be set if
+	 * {@link #queryProvider(JpaQueryProvider)} has not been set.
+	 *
+	 * @param queryString the JPQL query
+	 * @return this instance for method chaining
+	 * @see JpaCursorItemReader#setQueryString(String)
+	 */
+	public JpaCursorItemReaderBuilder<T> queryString(String queryString) {
+		this.queryString = queryString;
+
+		return this;
+	}
+
+	/**
+	 * The {@link EntityManagerFactory} to be used for executing the configured
+	 * {@link #queryString}.
+	 *
+	 * @param entityManagerFactory {@link EntityManagerFactory} used to create
+	 * {@link javax.persistence.EntityManager}
+	 * @return this instance for method chaining
+	 */
+	public JpaCursorItemReaderBuilder<T> entityManagerFactory(EntityManagerFactory entityManagerFactory) {
+		this.entityManagerFactory = entityManagerFactory;
+
+		return this;
+	}
+
+	/**
+	 * Returns a fully constructed {@link JpaCursorItemReader}.
+	 *
+	 * @return a new {@link JpaCursorItemReader}
+	 */
+	public JpaCursorItemReader<T> build() {
+		Assert.notNull(this.entityManagerFactory, "An EntityManagerFactory is required");
+		if (this.saveState) {
+			Assert.hasText(this.name, "A name is required when saveState is set to true");
+		}
+		if (this.queryProvider == null) {
+			Assert.hasLength(this.queryString, "Query string is required when queryProvider is null");
+		}
+
+		JpaCursorItemReader<T> reader = new JpaCursorItemReader<>();
+		reader.setEntityManagerFactory(this.entityManagerFactory);
+		reader.setQueryProvider(this.queryProvider);
+		reader.setQueryString(this.queryString);
+		reader.setParameterValues(this.parameterValues);
+		reader.setCurrentItemCount(this.currentItemCount);
+		reader.setMaxItemCount(this.maxItemCount);
+		reader.setSaveState(this.saveState);
+		reader.setName(this.name);
+		return reader;
+	}
+}