[Hibernate] Failed to lazily initialize a collection

[SimonPM]

Hello,

I'm curruntly building a webapp built on the model of the petclinic sample app.

I am facing an error of initialization of a collection when executing a SimpleFormController. Hibernate says it doesn't find the session. I use HibernateTemplate to manage data access.

Here is the error :

net.sf.hibernate.LazyInitializationException: Failed to lazily initialize a collection - no session or session was closed at net.sf.hibernate.collection.PersistentCollection.initialize(PersistentCollection.java:209) at net.sf.hibernate.collection.PersistentCollection.read(PersistentCollection.java:71) at net.sf.hibernate.collection.Set.toString(Set.java:217) at java.lang.String.valueOf(Unknown Source) at java.lang.StringBuffer.append(Unknown Source) at com.spm.bulletin.Entity.toString(Entity.java:66) at java.lang.String.valueOf(Unknown Source) at java.util.AbstractCollection.toString(Unknown Source) at java.lang.String.valueOf(Unknown Source) at java.lang.StringBuffer.append(Unknown Source) at com.spm.bulletin.web.AddPupilsClassForm.onSubmit(AddPupilsClassForm.java:44) at org.springframework.web.servlet.mvc.SimpleFormController.processFormSubmission(SimpleFormController.java:248) at org.springframework.web.servlet.mvc.AbstractFormController.handleRequestInternal(AbstractFormController.java:243) at org.springframework.web.servlet.mvc.AbstractController.handleRequest(AbstractController.java:128) at org.springframework.web.servlet.mvc.SimpleControllerHandlerAdapter.handle(SimpleControllerHandlerAdapter.java:44) at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:675) at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:623) at org.springframework.web.servlet.FrameworkServlet.serviceWrapper(FrameworkServlet.java:384) at org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:353) at javax.servlet.http.HttpServlet.service(HttpServlet.java:716) at javax.servlet.http.HttpServlet.service(HttpServlet.java:809) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:200) at

Here is the XML declaration of the addClassForm bean :

	<bean id="addClassForm" class="com.spm.bulletin.web.AddPupilsClassForm">
		<property name="formView"><value>classForm</value></property>
		<property name="successView"><value>classRedirect</value></property>
		<property name="validator"><ref local="classValidator"/></property>
		<property name="school"><ref bean="school"/></property>
	</bean>

The Java class extending SimpleFormController :

public class AddPupilsClassForm extends AbstractSchoolForm {

	public AddPupilsClassForm() {
		// OK to start with a blank command object
		setCommandClass(PupilsClass.class);
		// activate session form mode to allow for detection of duplicate submissions
		setSessionForm(true);
	}

	protected Map referenceData(HttpServletRequest request) throws ServletException {
		Map refData = new HashMap();
		refData.put("teachers", getSchool().getTeachers());
		return refData;
	}
	
	/** Method inserts a new <code>PupilsClass</code>. */
	protected ModelAndView onSubmit&#40;HttpServletRequest request, HttpServletResponse response, Object command, BindException arg3&#41; throws ServletException &#123;
		PupilsClass pupilsClass = &#40;PupilsClass&#41; command;
		int mainTeacherId = Integer.parseInt&#40;request.getParameter&#40;"mainTeacherId"&#41;&#41;;
		System.out.println&#40;"mainTeacherId &#58; "+mainTeacherId&#41;;
		if &#40;mainTeacherId != -1&#41; &#123;
			System.out.println&#40;"teachers &#58; " + getSchool&#40;&#41;.getTeachers&#40;&#41;&#41;;
			Teacher teacher = &#40;Teacher&#41;Entity.getById&#40;getSchool&#40;&#41;.getTeachers&#40;&#41;, Teacher.class, mainTeacherId&#41;;
			//System.out.println&#40;"pupilsClass &#58; "+pupilsClass&#41;;
			pupilsClass.setMainTeacher&#40;teacher&#41;;
		&#125;
		System.out.println&#40;"pupilsClass &#58; " + pupilsClass&#41;;
		//pupilsClass.setMainTeacher&#40;getSchool&#40;&#41;.loadTeacher&#40;pupilsClass.getMainTeacher&#40;&#41;.getId&#40;&#41;&#41;&#41;;
		// delegate the insert to the Business layer
		getSchool&#40;&#41;.storePupilsClass&#40;pupilsClass&#41;;
		return new ModelAndView&#40;getSuccessView&#40;&#41;, "pupilsClassId", Integer.toString&#40;pupilsClass.getId&#40;&#41;&#41;&#41;;
	&#125;

	protected ModelAndView handleInvalidSubmit&#40;HttpServletRequest request, HttpServletResponse response&#41;
			throws Exception &#123;
		return disallowDuplicateFormSubmission&#40;request, response&#41;;
	&#125;

&#125;

The error is thrown when calling the getSchool().getTeachers() method in the onSubmit(...).

And the class managing data access :

public class HibernateSchool extends HibernateDaoSupport implements School {

	public Collection getTeachers() throws DataAccessException {
		return getHibernateTemplate().find("from Teacher teacher order by teacher.lastName, teacher.firstName");
	}
[...]

[Costin Leau]

This is more of a Data Access problem. Your objects are lazy-init and I assume you are not using OpenSessionInViewFilter/Interceptor.
I am not familiar with the PetClinit application on Spring but a quick fix would be disable the lazy functionality of your objects - ofc, this thing has it's consequences.