Hibernate session is null when executing SQL query

Question

When executing a SQL native query with SQLQuery q = session.createSQLQuery(query).addEntity("edu", StudentEduPojo.class); JVM throws a null pointer exception.

DBConnectionDao.class

package com.ms.avalon.master.dao.rdbms;

import javax.sql.DataSource;

import org.apache.commons.dbcp.BasicDataSource;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.jdbc.core.namedparam.NamedParameterJdbcTemplate;
import org.springframework.orm.hibernate3.HibernateTemplate;
import org.springframework.stereotype.Repository;

@Repository
public class DBConnectionDao {

    protected Session session;
    protected DataSource dataSource;
    protected SessionFactory sessionFactory;
    protected HibernateTemplate hibernateTemplate=null;
    protected NamedParameterJdbcTemplate namedJdbcTemplate=null;

    @Autowired
    public void setDataSource(DataSource dataSource) {
        this.dataSource = dataSource;
        namedJdbcTemplate=new NamedParameterJdbcTemplate(dataSource);
    }

    @Autowired
    public void setSessionFactory(SessionFactory sessionFactory) {
        System.out.println("session created");
        this.sessionFactory = sessionFactory;
        session = sessionFactory.getCurrentSession();
        hibernateTemplate=new HibernateTemplate(sessionFactory);
    }
}

PlacementDaoRdbms.class

package com.ms.avalon.master.dao.rdbms;

import java.util.ArrayList;
import java.util.List;

import org.hibernate.SQLQuery;
import org.hibernate.criterion.DetachedCriteria;
import com.ms.avalon.master.beans.PlacementCaseBean;
import com.ms.avalon.master.dao.PlacementDao;
import com.ms.avalon.master.formbeans.PlacementFormBean;
import com.ms.avalon.master.pojos.studentpojos.StudentEduPojo;
import com.ms.avalon.master.pojos.studentpojos.StudentTestPojo;

public class PlacementDaoRdbms extends DBConnectionDao implements PlacementDao {

    @Override
    public List<StudentEduPojo> searchWithCases(PlacementCaseBean caseBean, PlacementFormBean placementBean) {

        String query = "Some complicated SQL query";

        SQLQuery q = session.createSQLQuery(query)
        .addEntity("edu", StudentEduPojo.class);

        List<StudentEduPojo> list = q.list();

        return list;
    }

}

When using the function createSqlQuery on session in PlacementDaoRdbms, I get a NPE.

Following is the stack trace:

May 11, 2016 8:52:17 PM org.apache.catalina.core.StandardWrapperValve invoke SEVERE: Servlet.service() for servlet [dispatcher] in context with path [/Avalon-1.0] threw exception [Request processing failed; nested exception is java.lang.NullPointerException] with root cause java.lang.NullPointerException at com.ms.avalon.master.dao.rdbms.PlacementDaoRdbms.searchWithCases(PlacementDaoRdbms.java:108) at com.ms.avalon.master.business.TalentCaseHandler.searchForCases(TalentCaseHandler.java:61) at com.ms.avalon.master.service.impl.PlacementServiceImpl.searchForTalent(PlacementServiceImpl.java:26) at com.ms.avalon.master.controllers.PlacementController.searchForTalent(PlacementController.java:29) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source) at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) at java.lang.reflect.Method.invoke(Unknown Source) at org.springframework.web.bind.annotation.support.HandlerMethodInvoker.invokeHandlerMethod(HandlerMethodInvoker.java:176) at org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter.invokeHandlerMethod(AnnotationMethodHandlerAdapter.java:427) at org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter.handle(AnnotationMethodHandlerAdapter.java:415) at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:788) at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:717) at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:644) at org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:560) at javax.servlet.http.HttpServlet.service(HttpServlet.java:646) at javax.servlet.http.HttpServlet.service(HttpServlet.java:727) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:303) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208) at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208) at com.opensymphony.module.sitemesh.filter.PageFilter.parsePage(PageFilter.java:119) at com.opensymphony.module.sitemesh.filter.PageFilter.doFilter(PageFilter.java:55) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208) at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:220) at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:122) at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:504) at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:170) at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:103) at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:950) at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:116) at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:421) at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1074) at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:611) at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:316) at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source) at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source) at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) at java.lang.Thread.run(Unknown Source)

Also, is this the correct way to use session from the parent class?

Thanks for the help :)

Answer 1

The method searchWithCases in PlacementDaoRdbms was being called from another class (let's call that A). I was creating A's object using new keyword, which was causing DI and @Autowired to not work. I know I should have posted the full code but still, thanks for the help and advice. Let me know if you've got a similar problem :)