Portlet has throws null portlet bag error when Indexer-class entry is made to liferay-portlet.xml and BaseIndexer class is extended by portlet.

Could you please post server error console log here ?

I have had the same problems before but most of the times it's related to corrupt xml , try and check with some wrong white spaces, line breaks.If it's still there give the complete stack trace here

The portlet in question throws this error when deployed

at com.liferay.portal.kernel.deploy.hot.BaseHotDeployListener.throwHotDeployException(BaseHotDeployListener.java:45)
at com.liferay.portal.deploy.hot.PortletHotDeployListener.invokeDeploy(PortletHotDeployListener.java:104)
at com.liferay.portal.kernel.deploy.hot.HotDeployUtil._doFireDeployEvent(HotDeployUtil.java:109)
at com.liferay.portal.kernel.deploy.hot.HotDeployUtil._fireDeployEvent(HotDeployUtil.java:182)
at com.liferay.portal.kernel.deploy.hot.HotDeployUtil.fireDeployEvent(HotDeployUtil.java:38)
at com.liferay.portal.kernel.servlet.PortletContextListener.doPortalInit(PortletContextListener.java:99)
at com.liferay.portal.kernel.util.BasePortalLifecycle.portalInit(BasePortalLifecycle.java:42)
at com.liferay.portal.kernel.util.PortalLifecycleUtil.register(PortalLifecycleUtil.java:52)
at com.liferay.portal.kernel.util.BasePortalLifecycle.registerPortalLifecycle(BasePortalLifecycle.java:50)
at com.liferay.portal.kernel.servlet.PortletContextListener.contextInitialized(PortletContextListener.java:55)
at org.apache.catalina.core.StandardContext.listenerStart(StandardContext.java:4135)
at org.apache.catalina.core.StandardContext.start(StandardContext.java:4630)
at org.apache.catalina.core.StandardContext.reload(StandardContext.java:3391)
at org.apache.catalina.loader.WebappLoader.backgroundProcess(WebappLoader.java:426)
at org.apache.catalina.core.ContainerBase.backgroundProcess(ContainerBase.java:1309)
at org.apache.catalina.core.ContainerBase$ContainerBackgroundProcessor.processChildren(ContainerBase.java:1601)
at org.apache.catalina.core.ContainerBase$ContainerBackgroundProcessor.processChildren(ContainerBase.java:1610)
at org.apache.catalina.core.ContainerBase$ContainerBackgroundProcessor.processChildren(ContainerBase.java:1610)
at org.apache.catalina.core.ContainerBase$ContainerBackgroundProcessor.run(ContainerBase.java:1590)
at java.lang.Thread.run(Thread.java:619)
Caused by: java.lang.NullPointerException
at com.liferay.portal.kernel.search.IndexerRegistryUtil.register(IndexerRegistryUtil.java:41)
at com.liferay.portlet.PortletBagFactory.newIndexer(PortletBagFactory.java:573)
at com.liferay.portlet.PortletBagFactory.create(PortletBagFactory.java:128)
at com.liferay.portal.deploy.hot.PortletHotDeployListener.initPortlet(PortletHotDeployListener.java:456)
at com.liferay.portal.deploy.hot.PortletHotDeployListener.doInvokeDeploy(PortletHotDeployListener.java:253)
at com.liferay.portal.deploy.hot.PortletHotDeployListener.invokeDeploy(PortletHotDeployListener.java:101)
... 18 more

and when search portlet is used for searching,this error is thrown

09:00:43,252 ERROR [PortletContextFactory:75] Portlet wantportlet_WAR_Wantportlet has a null portlet bag
09:00:43,252 ERROR [IncludeTag:231] Current URL /en_GB/web/guest/home?p_p_id=3&p_p_lifecycle=0&p_p_state=maximized&p_p_mode=view&p_p_col_id=column-1&p_p_col_count=3&_3_struts_action=%2Fsearch%2Fsearch generates exception: An exception occurred processing JSP page /html/portlet/search/search.jsp at line 39

36:
37: List<Portlet> portlets = PortletLocalServiceUtil.getPortlets(company.getCompanyId(), includeSystemPortlets, false);
38:
39: portlets = ListUtil.sort(portlets, new PortletTitleComparator(application, locale));
40:
41: Iterator itr = portlets.iterator();
42:


Stacktrace:
09:00:43,252 ERROR [IncludeTag:154] java.lang.NullPointerException
at com.liferay.portlet.PortletContextFactory._create(PortletContextFactory.java:82)
at com.liferay.portlet.PortletContextFactory.create(PortletContextFactory.java:41)
at com.liferay.portlet.PortletConfigFactoryImpl.create(PortletConfigFactoryImpl.java:53)
at com.liferay.portlet.PortletConfigFactoryUtil.create(PortletConfigFactoryUtil.java:31)
at com.liferay.portal.util.PortalImpl.getPortletTitle(PortalImpl.java:2538)
at com.liferay.portal.util.PortalUtil.getPortletTitle(PortalUtil.java:774)
at com.liferay.portal.util.comparator.PortletTitleComparator.compare(PortletTitleComparator.java:52)
at com.liferay.portal.util.comparator.PortletTitleComparator.compare(PortletTitleComparator.java:1)

I seem to be having this same issue. Where you able to resolve the problem? If so could you be so kind as to explain how?

Seems I'd forgotten to change the null being returned from the getClassNames method that was generated by Eclipse. Now that I'm returning the class names it works.

Can you please explain...
i am facing same erro r while deploying my application.war on liferay 6.1 + jboss 7

7:43:55,841 INFO (MSC service thread 1-4) 07:43:55,841 ERROR [MSC service thread 1-4][PortletContextFactory:73] Portlet youraccount_WAR_clientportal has a null portlet bag

07:43:55,841 INFO (MSC service thread 1-4) 07:43:55,841 ERROR [MSC service thread 1-4][BasePortalLifecycle:45] java.lang.NullPointerException

07:43:55,841 INFO (MSC service thread 1-4) java.lang.NullPointerException

07:43:55,841 INFO (MSC service thread 1-4) at com.liferay.portlet.PortletContextFactory._create(PortletContextFactory.java:80)

07:43:55,841 INFO (MSC service thread 1-4) at com.liferay.portlet.PortletContextFactory.create(PortletContextFactory.java:39)

I got the same error and I've solved it. in my case it was a bug in the portlet action class, where i was taking a parameter declared as a global variable.
If you invoke it within the metod the "null portlet bag" error is fixed. if you declare and inizialize "archivePath" as a global class variable you get the null portlet bag error.
The right way is this:

public void refreshDatabase(ActionRequest actionRequest,
ActionResponse response) throws Exception {

String archivePath = getInitParameter("archive-folder");
logger.info("Refresh Database clicked");
try {
DBUtil.refreshDatabase(archivePath);
SessionMessages.add(actionRequest, "success-db");
SessionMessages.add(actionRequest, "tables-up");
} catch (Exception e) {
SessionErrors.add(actionRequest, "error-db");
}
}

I hope it helps :-)