java.lang.IllegalStateException: Cannot call isReadOnlyBeforeAttachedToSession when isReadOnlySettingAvailable == true
   org.hibernate.proxy.AbstractLazyInitializer.isReadOnlyBeforeAttachedToSession(AbstractLazyInitializer.java:277)
   sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
   sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
   sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
   java.lang.reflect.Method.invoke(Method.java:616)
   flexjson.BeanProperty.getValue(BeanProperty.java:102)
   flexjson.transformer.ObjectTransformer.transform(ObjectTransformer.java:37)
   flexjson.transformer.TransformerWrapper.transform(TransformerWrapper.java:22)
   flexjson.transformer.ObjectTransformer.transform(ObjectTransformer.java:49)
   flexjson.transformer.TransformerWrapper.transform(TransformerWrapper.java:22)
   flexjson.transformer.ObjectTransformer.transform(ObjectTransformer.java:49)
   flexjson.transformer.TransformerWrapper.transform(TransformerWrapper.java:22)
   flexjson.transformer.ObjectTransformer.transform(ObjectTransformer.java:49)
   flexjson.transformer.TransformerWrapper.transform(TransformerWrapper.java:22)
   flexjson.JSONContext.transform(JSONContext.java:73)
   flexjson.transformer.IterableTransformer.transform(IterableTransformer.java:29)
   flexjson.transformer.TransformerWrapper.transform(TransformerWrapper.java:22)
   flexjson.JSONContext.transform(JSONContext.java:73)
   flexjson.JSONSerializer.serialize(JSONSerializer.java:377)
   flexjson.JSONSerializer.serialize(JSONSerializer.java:235)
   org.xxxxx.controller.admin.RecycleBinController.getDeletedDocsJson(RecycleBinController.java:69)
   sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
   sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
   sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
   java.lang.reflect.Method.invoke(Method.java:616)
   org.springframework.web.method.support.InvocableHandlerMethod.invoke(InvocableHandlerMethod.java:212)
   org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:126)
   org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:96)
   org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:617)
   org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:578)
   org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:80)
   org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:900)
   org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:827)
   org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:882)
   org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:778)
   javax.servlet.http.HttpServlet.service(HttpServlet.java:621)
   javax.servlet.http.HttpServlet.service(HttpServlet.java:722)
   org.xxxxx.filter.PagePreviewFilter.doFilter(PagePreviewFilter.java:62)
   net.sf.ehcache.constructs.web.filter.GzipFilter.doFilter(GzipFilter.java:95)
   net.sf.ehcache.constructs.web.filter.Filter.doFilter(Filter.java:86)
   org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:88)
   org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:76)
   org.springframework.web.filter.HiddenHttpMethodFilter.doFilterInternal(HiddenHttpMethodFilter.java:77)
   org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:76)
   org.salvationarmy.commons.filters.HttpHeadFilter.doFilter(HttpHeadFilter.java:47)
   org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:369)
   org.springframework.security.web.access.intercept.FilterSecurityInterceptor.invoke(FilterSecurityInterceptor.java:109)
   org.springframework.security.web.access.intercept.FilterSecurityInterceptor.doFilter(FilterSecurityInterceptor.java:83)
   org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:381)
   org.springframework.security.web.access.ExceptionTranslationFilter.doFilter(ExceptionTranslationFilter.java:97)
   org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:381)
   org.springframework.security.web.savedrequest.RequestCacheAwareFilter.doFilter(RequestCacheAwareFilter.java:35)
   org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:381)
   org.springframework.security.web.authentication.AbstractAuthenticationProcessingFilter.doFilter(AbstractAuthenticationProcessingFilter.java:187)
   org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:381)
   org.springframework.security.web.authentication.logout.LogoutFilter.doFilter(LogoutFilter.java:105)
   org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:381)
   org.springframework.security.web.context.SecurityContextPersistenceFilter.doFilter(SecurityContextPersistenceFilter.java:79)
   org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:381)
   org.springframework.security.web.FilterChainProxy.doFilter(FilterChainProxy.java:168)
   org.springframework.web.filter.DelegatingFilterProxy.invokeDelegate(DelegatingFilterProxy.java:346)
   org.springframework.web.filter.DelegatingFilterProxy.doFilter(DelegatingFilterProxy.java:259)

@FullTextFilterDefs({ @FullTextFilterDef(name = "site", impl = SiteFilterFactory.class),
        @FullTextFilterDef(name = "published", impl = PublishedFilterFactory.class) })
@Entity(name = "document")
@DiscriminatorColumn(name = "DTYPE", discriminatorType = DiscriminatorType.STRING)
@Audited(targetAuditMode = RelationTargetAuditMode.NOT_AUDITED)
public abstract class Document<T extends Document<?>> extends ModelObject implements Serializable, Comparable<T>,
        Versionable {
/* many properties here. All of them work fine */
}

@Indexed(index = "content")
@Entity(name = "webpage")
@DiscriminatorValue("webpage")
@Audited
@Cacheable(true)
@Cache(usage = CacheConcurrencyStrategy.READ_WRITE, region = "modelObjectCache")
public class WebPage extends Document<WebPage> {

    private static final long serialVersionUID = 7045089818690794735L;

    @NotNull
    @ForeignKey(name = "TO_STRUCTURE_FK", inverseName = "TO_DOCUMENT_FK")
    @OneToOne(mappedBy = "document", cascade = CascadeType.ALL, fetch = FetchType.LAZY)
    @Fetch(FetchMode.JOIN)
    @NotAudited
    private Structure structure;
   
/* getters and setters here */
}

@Entity(name = "structure")
@Cacheable(true)
@Cache(usage = CacheConcurrencyStrategy.READ_WRITE, region = "modelObjectCache")
public class Structure extends ModelObject implements Serializable, Comparable<Structure> {

    /* The problem is with this property. If the getter for this property has @JSON(include=false) then the serialization works fine.  */
    @ManyToOne(fetch = FetchType.LAZY)
    @JoinColumn(name = "fkParent")
    @ForeignKey(name = "TO_PARENT_FK", inverseName = "TO_STRUCTURE_FK")
    private WebPage parent;

    @NotNull
    @OneToOne(fetch = FetchType.LAZY)
    @JoinColumn(name = "fkDocument")
    @ForeignKey(name = "TO_DOCUMENT_FK", inverseName = "TO_STRUCTURE_FK")
    @ContainedIn
    private WebPage document;

    /* getters and setters here. */

}

@SuppressWarnings("rawtypes")
    @RequestMapping(value = "recycle_bin/json", method = RequestMethod.GET)
    public @ResponseBody
    String getDeletedDocsJson(@PathVariable("siteUrlAlias") String urlAlias, HttpServletResponse response) {
        Site site = siteService.getSite(urlAlias);
        List<Document> deletedDocs = docService.getDeletedDocs(site);

        /* I have confirmed that deletedDocs is successfully populated */

        JSONSerializer serializer = new JSONSerializer();
        serializer.exclude("*.class");
        serializer.exclude("*.content");
        serializer.transform(new MapTransformer(), Map.class);
        serializer.transform(new DateTransformer("yyyy-MM-dd'T'HH:mm:ssZ"), Date.class);
        response.setContentType("application/json");
        return serializer.serialize(deletedDocs);
    }