Introduce a builder for the HibernatePagingItemReader

This commit creates a builder for the HibernatePagingItemReader.

Resolves BATCH-2588

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

@@ -49,7 +49,7 @@ public class HibernateItemReaderHelper<T> implements InitializingBean {
 
 	private String queryName = "";
 
-	private HibernateQueryProvider<T> queryProvider;
+	private HibernateQueryProvider<? extends T> queryProvider;
 
 	private boolean useStatelessSession = true;
 
@@ -74,7 +74,7 @@ public class HibernateItemReaderHelper<T> implements InitializingBean {
 	/**
 	 * @param queryProvider Hibernate query provider
 	 */
-	public void setQueryProvider(HibernateQueryProvider<T> queryProvider) {
+	public void setQueryProvider(HibernateQueryProvider<? extends T> queryProvider) {
 		this.queryProvider = queryProvider;
 	}
 
@@ -108,11 +108,6 @@ public class HibernateItemReaderHelper<T> implements InitializingBean {
 			Assert.state(StringUtils.hasText(queryString) ^ StringUtils.hasText(queryName),
 					"queryString or queryName must be set");
 		}
-		// making sure that the appropriate (Hibernate) query provider is set
-		else {
-			Assert.state(queryProvider != null, "Hibernate query provider must be set");
-		}
-
 	}
 
 	/**

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

@@ -60,7 +60,7 @@ import org.springframework.util.ClassUtils;
 public class HibernatePagingItemReader<T> extends AbstractPagingItemReader<T> 
                 implements InitializingBean {
 
-	private HibernateItemReaderHelper<T> helper = new HibernateItemReaderHelper<T>();
+	private HibernateItemReaderHelper<T> helper = new HibernateItemReaderHelper<>();
 
 	private Map<String, Object> parameterValues;
 
@@ -108,7 +108,7 @@ public class HibernatePagingItemReader<T> extends AbstractPagingItemReader<T>
 	 *
 	 * @param queryProvider Hibernate query provider
 	 */
-	public void setQueryProvider(HibernateQueryProvider<T> queryProvider) {
+	public void setQueryProvider(HibernateQueryProvider<? extends T> queryProvider) {
 		helper.setQueryProvider(queryProvider);
 	}
 

spring-batch-infrastructure/src/main/java/org/springframework/batch/item/database/builder/HibernateCursorItemReaderBuilder.java

@@ -148,7 +148,7 @@ public class HibernateCursorItemReaderBuilder<T> {
 	/**
 	 * The Hibernate {@link SessionFactory} to execute the query against.
 	 *
-	 * @param sessionFactory the session factorry
+	 * @param sessionFactory the session factory
 	 * @return this instance for method chaining
 	 * @see HibernateCursorItemReader#setSessionFactory(SessionFactory)
 	 */

spring-batch-infrastructure/src/main/java/org/springframework/batch/item/database/builder/HibernatePagingItemReaderBuilder.java

@@ -0,0 +1,268 @@
+/*
+ * Copyright 2017 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
+ *
+ *      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 org.springframework.batch.item.database.builder;
+
+import java.util.Map;
+
+import org.hibernate.SessionFactory;
+
+import org.springframework.batch.item.database.HibernatePagingItemReader;
+import org.springframework.batch.item.database.orm.HibernateQueryProvider;
+import org.springframework.util.Assert;
+import org.springframework.util.StringUtils;
+
+/**
+ * A builder for the {@link HibernatePagingItemReader}.  When configuring, only one of the
+ * following should be provided:
+ * <ul>
+ *     <li>{@link #queryString(String)}</li>
+ *     <li>{@link #queryName(String)}</li>
+ *     <li>{@link #queryProvider(HibernateQueryProvider)}</li>
+ * </ul>
+ *
+ * @author Michael Minella
+ * @since 4.0
+ * @see HibernatePagingItemReader
+ */
+public class HibernatePagingItemReaderBuilder<T> {
+
+	private String name;
+
+	private int currentItem = 0;
+
+	private int maxItemCount = Integer.MAX_VALUE;
+
+	private boolean saveState = true;
+
+	private int pageSize = 10;
+
+	private Map<String, Object> parameterValues;
+
+	private String queryName;
+
+	private int fetchSize;
+
+	private HibernateQueryProvider<? extends T> queryProvider;
+
+	private String queryString;
+
+	private SessionFactory sessionFactory;
+
+	private boolean statelessSession = true;
+
+	/**
+	 * A name used to prevent key collisions while saving the state in the
+	 * {@link org.springframework.batch.item.ExecutionContext}
+	 *
+	 * @param name unique name for this reader instance
+	 * @return this instance for method chaining
+	 * @see HibernatePagingItemReader#setName(String)
+	 */
+	public HibernatePagingItemReaderBuilder<T> name(String name) {
+		this.name = name;
+
+		return this;
+	}
+
+	/**
+	 * Index for the current item.  Used on restarts to indicate where to start from.
+	 *
+	 * @param currentItem current index
+	 * @return this instance for method chaining
+	 * @see HibernatePagingItemReader#setCurrentItemCount(int)
+	 */
+
+	public HibernatePagingItemReaderBuilder<T> currentItem(int currentItem) {
+		this.currentItem = currentItem;
+
+		return this;
+	}
+
+	/**
+	 * The index of the max item to be read.
+	 *
+	 * @param maxItemCount max index
+	 * @return this instance for method chaining
+	 * @see HibernatePagingItemReader#setMaxItemCount(int)
+	 */
+	public HibernatePagingItemReaderBuilder<T> maxItemCount(int maxItemCount) {
+		this.maxItemCount = maxItemCount;
+
+		return this;
+	}
+
+	/**
+	 * Indicates if the state should be saved.  If set to false, restarts will begin at
+	 * the beginning of the dataset.  Defaults to true
+	 *
+	 * @param saveState indicator
+	 * @return this instance for method chaining
+	 * @see HibernatePagingItemReader#setSaveState(boolean)
+	 */
+	public HibernatePagingItemReaderBuilder<T> saveState(boolean saveState) {
+		this.saveState = saveState;
+
+		return this;
+	}
+
+	/**
+	 * The number of records to request per page/query.  Defaults to 10.  Must be greater
+	 * than zero.
+	 *
+	 * @param pageSize number of items
+	 * @return this instance for method chaining
+	 * @see HibernatePagingItemReader#setPageSize(int)
+	 */
+	public HibernatePagingItemReaderBuilder<T> pageSize(int pageSize) {
+		this.pageSize = pageSize;
+
+		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 HibernatePagingItemReader#setParameterValues(Map)
+	 */
+	public HibernatePagingItemReaderBuilder<T> parameterValues(Map<String, Object> parameterValues) {
+		this.parameterValues = parameterValues;
+
+		return this;
+	}
+
+	/**
+	 * The name of the Hibernate named query to be executed for this reader.
+	 *
+	 * @param queryName name of the query to execute
+	 * @return this instance for method chaining
+	 * @see HibernatePagingItemReader#setQueryName(String)
+	 */
+	public HibernatePagingItemReaderBuilder<T> queryName(String queryName) {
+		this.queryName = queryName;
+
+		return this;
+	}
+
+	/**
+	 * Fetch size used internally by Hibernate to limit amount of data fetched
+	 * from database per round trip.
+	 *
+	 * @param fetchSize number of records
+	 * @return this instance for method chaining
+	 * @see HibernatePagingItemReader#setFetchSize(int)
+	 */
+	public HibernatePagingItemReaderBuilder<T> fetchSize(int fetchSize) {
+		this.fetchSize = fetchSize;
+
+		return this;
+	}
+
+	/**
+	 * A query provider.  This should be set only if {@link #queryString(String)} and
+	 * {@link #queryName(String)} have not been set.
+	 *
+	 * @param queryProvider the query provider
+	 * @return this instance for method chaining
+	 * @see HibernatePagingItemReader#setQueryProvider(HibernateQueryProvider)
+	 */
+	public HibernatePagingItemReaderBuilder<T> queryProvider(HibernateQueryProvider queryProvider) {
+		this.queryProvider = queryProvider;
+
+		return this;
+	}
+
+	/**
+	 * The HQL query string to execute.  This should only be set if
+	 * {@link #queryProvider(HibernateQueryProvider)} and {@link #queryName(String)} have
+	 * not been set.
+	 *
+	 * @param queryString the HQL query
+	 * @return this instance for method chaining
+	 * @see HibernatePagingItemReader#setQueryString(String)
+	 */
+	public HibernatePagingItemReaderBuilder<T> queryString(String queryString) {
+		this.queryString = queryString;
+
+		return this;
+	}
+
+	/**
+	 * The Hibernate {@link SessionFactory} to execute the query against.
+	 *
+	 * @param sessionFactory the session factory
+	 * @return this instance for method chaining
+	 * @see HibernatePagingItemReader#setSessionFactory(SessionFactory)
+	 */
+	public HibernatePagingItemReaderBuilder<T> sessionFactory(SessionFactory sessionFactory) {
+		this.sessionFactory = sessionFactory;
+
+		return this;
+	}
+
+	/**
+	 * Indicator for whether to use a {@link org.hibernate.StatelessSession}
+	 * (<code>true</code>) or a {@link org.hibernate.Session} (<code>false</code>).
+	 *
+	 * @param useStatelessSession Defaults to false
+	 * @return this instance for method chaining
+	 * @see HibernatePagingItemReader#setUseStatelessSession(boolean)
+	 */
+	public HibernatePagingItemReaderBuilder<T> useSatelessSession(boolean useStatelessSession) {
+		this.statelessSession = useStatelessSession;
+
+		return this;
+	}
+
+	/**
+	 * Returns a fully constructed {@link HibernatePagingItemReader}.
+	 *
+	 * @return a new {@link HibernatePagingItemReader}
+	 */
+	public HibernatePagingItemReader<T> build() {
+		Assert.notNull(this.sessionFactory, "A SessionFactory must be provided");
+		Assert.state(this.fetchSize >= 0, "fetchSize must not be negative");
+
+		if(this.saveState) {
+			Assert.hasText(this.name,
+					"A name is required when saveState is set to true");
+		}
+
+		if(this.queryProvider == null) {
+			Assert.state(StringUtils.hasText(queryString) ^ StringUtils.hasText(queryName),
+					"queryString or queryName must be set");
+		}
+
+		HibernatePagingItemReader<T> reader = new HibernatePagingItemReader<>();
+
+		reader.setSessionFactory(this.sessionFactory);
+		reader.setSaveState(this.saveState);
+		reader.setMaxItemCount(this.maxItemCount);
+		reader.setCurrentItemCount(this.currentItem);
+		reader.setName(this.name);
+		reader.setFetchSize(this.fetchSize);
+		reader.setParameterValues(this.parameterValues);
+		reader.setQueryName(this.queryName);
+		reader.setQueryProvider(this.queryProvider);
+		reader.setQueryString(this.queryString);
+		reader.setPageSize(this.pageSize);
+		reader.setUseStatelessSession(this.statelessSession);
+
+		return reader;
+	}
+}