OPEN - issue BATCH-1422: HibernateCursorItemReader causes OutOfMemoryError when skipping large sets of data

Javadocs.

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

@@ -35,8 +35,10 @@ import org.springframework.util.ClassUtils;
  * executes the HQL query when initialized iterates over the result set as
  * {@link #read()} method is called, returning an object corresponding to
  * current row. The query can be set directly using
- * {@link #setQueryString(String)} or a named query can be used by
- * {@link #setQueryName(String)}.
+ * {@link #setQueryString(String)}, a named query can be used by
+ * {@link #setQueryName(String)}, or a query provider strategy can be supplied
+ * via {@link #setQueryProvider(HibernateQueryProvider)}.
+ * 
  * 
  * <p>
  * The reader can be configured to use either {@link StatelessSession}
@@ -165,7 +167,7 @@ public class HibernateCursorItemReader<T> extends AbstractItemCountingItemStream
 		cursor = helper.getForwardOnlyCursor();
 		initialized = true;
 	}
-	
+
 	/**
 	 * Update the context and clear the session if stateful.
 	 * 

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

@@ -26,16 +26,18 @@ import org.hibernate.Session;
 import org.hibernate.SessionFactory;
 import org.hibernate.StatelessSession;
 import org.springframework.batch.item.database.support.AbstractHibernateQueryProvider;
+import org.springframework.beans.factory.InitializingBean;
 import org.springframework.util.Assert;
 import org.springframework.util.StringUtils;
 
 /**
- * Internal shared state helper for hibernate readers.
+ * Internal shared state helper for hibernate readers managing sessions and
+ * queries.
  * 
  * @author Dave Syer
  * 
  */
-class HibernateItemReaderHelper<T> {
+class HibernateItemReaderHelper<T> implements InitializingBean {
 
 	private SessionFactory sessionFactory;
 
@@ -170,7 +172,7 @@ class HibernateItemReaderHelper<T> {
 			}
 		}
 
-		// if queryProvider is set use it to create a query
+		// If queryProvider is set use it to create a query
 		return queryProvider.createQuery();
 
 	}
@@ -203,8 +205,11 @@ class HibernateItemReaderHelper<T> {
 	}
 
 	/**
-	 * @param page the page to read
-	 * @param pageSize the size of the page
+	 * Read a page of data, clearing the existing session (if necessary) first,
+	 * and creating a new session before executing the query.
+	 * 
+	 * @param page the page to read (starting at 0)
+	 * @param pageSize the size of the page or maximum number of items to read
 	 * @return a collection of items
 	 */
 	public Collection<? extends T> readPage(int page, int pageSize) {
@@ -225,7 +230,7 @@ class HibernateItemReaderHelper<T> {
 	 * Clear the session if stateful.
 	 */
 	public void clear() {
-		if (statefulSession!=null) {
+		if (statefulSession != null) {
 			statefulSession.clear();
 		}
 	}

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

@@ -28,12 +28,13 @@ import org.springframework.beans.factory.InitializingBean;
 import org.springframework.util.ClassUtils;
 
 /**
- * {@link ItemReader} for reading database records built on top of Hibernate. It
- * executes the HQL query when initialized iterates over the result set as
- * {@link #read()} method is called, returning an object corresponding to
- * current row. The query can be set directly using
- * {@link #setQueryString(String)} or a named query can be used by
- * {@link #setQueryName(String)}.
+ * {@link ItemReader} for reading database records built on top of Hibernate and
+ * reading only up to a fixed number of items at a time. It executes an HQL
+ * query when initialized is paged as the {@link #read()} method is called. The
+ * query can be set directly using {@link #setQueryString(String)}, a named
+ * query can be used by {@link #setQueryName(String)}, or a query provider
+ * strategy can be supplied via
+ * {@link #setQueryProvider(HibernateQueryProvider)}.
  * 
  * <p>
  * The reader can be configured to use either {@link StatelessSession}
@@ -63,11 +64,6 @@ public class HibernatePagingItemReader<T> extends AbstractPagingItemReader<T> im
 		setName(ClassUtils.getShortName(HibernatePagingItemReader.class));
 	}
 
-	public void afterPropertiesSet() throws Exception {
-		super.afterPropertiesSet();
-		helper.afterPropertiesSet();
-	}
-
 	/**
 	 * The parameter values to apply to a query (map of name:value).
 	 * 
@@ -131,6 +127,11 @@ public class HibernatePagingItemReader<T> extends AbstractPagingItemReader<T> im
 		helper.setUseStatelessSession(useStatelessSession);
 	}
 
+	public void afterPropertiesSet() throws Exception {
+		super.afterPropertiesSet();
+		helper.afterPropertiesSet();
+	}
+
 	@Override
 	protected void doOpen() throws Exception {
 		super.doOpen();
@@ -145,7 +146,7 @@ public class HibernatePagingItemReader<T> extends AbstractPagingItemReader<T> im
 		else {
 			results.clear();
 		}
-		
+
 		results.addAll(helper.readPage(getPage(), getPageSize()));
 
 	}