休眠：原因：java.lang.ClassCastException：[Ljava.lang.Object; 无法投射到 <package.Class>

Question

I have problem to fetch data from database and cast it to me needed type.

I try to cheak for the regestered user from database using Spring security. It works like: I insert userName and password and method loadUserByUserName(String userName) from UserDetailsServiceImpl class goes to database and cheaks for is the user exist in DB and if yes(user exist in DB) then fetch it from DB and authorize the user and render for him secure page. But problem is the in my DAO impl class method can't cast it to need me object - App1User my entity class and I see on login page message like this(Reason: [Ljava.lang.Object; cannot be cast to app1.domain.App1User enter code here ):

My method in DAOImpl class:

public App1User findUserByName(String userName) {


        Session session = sessionFactory.openSession();
        Transaction transaction = session.beginTransaction();
        List<App1User>  listUser = null;


        try {

            String stringSQL = "select au.userId, au.firstName, au.lastName, au.middleName, au.username, au.password, au.userPosition from App1User au where au.username = :userNameArg";
            Query query = session.createQuery(stringSQL);
            query.setParameter("userNameArg", userName);

            listUser = (List<App1User>)query.list();

            session.flush();    
            session.clear();
            transaction.commit();

        } catch(HibernateException e) {

            System.err.println(e);

            if(transaction != null)
                transaction.rollback();

        } finally {
            if(session != null)
                session.close();
        }

        return (App1User)listUser.get(0);
    }

My hibernate.hbm.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-configuration SYSTEM 
"http://www.hibernate.org/dtd/hibernate-configuration-3.0.dtd">

<hibernate-configuration>

   <session-factory>

       <property name="hibernate.current_session_context_class">thread</property> 

        <property name="hibernate.default_schema">PUBLIC</property>

        <!-- JDBC connection pool (use the built-in) -->
        <property name="connection.pool_size">1</property>

        <property name="hibernate.transaction.auto_close_session">false</property>

        <!-- SQL dialect -->
        <property name="dialect">org.hibernate.dialect.H2Dialect</property>

        <!-- Disable the second-level cache  -->
        <property name="cache.provider_class">org.hibernate.cache.internal.NoCacheProvider</property>

        <!-- Echo all executed SQL to stdout -->
        <property name="show_sql">true</property>

        <!-- Drop and re-create the database schema on startup -->
        <property name="hbm2ddl.auto">create</property>

        <mapping resource="/WEB-INF/hibernateConf/App1User.hbm.xml"/>

    </session-factory>

</hibernate-configuration>

The exception I have right now:

SEVERE: An internal error occurred while trying to authenticate the user.
org.springframework.security.authentication.InternalAuthenticationServiceException: [Ljava.lang.Object; cannot be cast to app1.domain.App1User
    at org.springframework.security.authentication.dao.DaoAuthenticationProvider.retrieveUser(DaoAuthenticationProvider.java:125)
    at org.springframework.security.authentication.dao.AbstractUserDetailsAuthenticationProvider.authenticate(AbstractUserDetailsAuthenticationProvider.java:143)
    at org.springframework.security.authentication.ProviderManager.authenticate(ProviderManager.java:167)
    at org.springframework.security.authentication.ProviderManager.authenticate(ProviderManager.java:192)
    at org.springframework.security.web.authentication.UsernamePasswordAuthenticationFilter.attemptAuthentication(UsernamePasswordAuthenticationFilter.java:93)
    at org.springframework.security.web.authentication.AbstractAuthenticationProcessingFilter.doFilter(AbstractAuthenticationProcessingFilter.java:217)
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:330)
    at org.springframework.security.web.authentication.logout.LogoutFilter.doFilter(LogoutFilter.java:120)
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:330)
    at org.springframework.security.web.csrf.CsrfFilter.doFilterInternal(CsrfFilter.java:120)
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:330)
    at org.springframework.security.web.header.HeaderWriterFilter.doFilterInternal(HeaderWriterFilter.java:64)
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:330)
    at org.springframework.security.web.context.request.async.WebAsyncManagerIntegrationFilter.doFilterInternal(WebAsyncManagerIntegrationFilter.java:53)
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:330)
    at org.springframework.security.web.context.SecurityContextPersistenceFilter.doFilter(SecurityContextPersistenceFilter.java:91)
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:330)
    at org.springframework.security.web.FilterChainProxy.doFilterInternal(FilterChainProxy.java:213)
    at org.springframework.security.web.FilterChainProxy.doFilter(FilterChainProxy.java:176)
    at org.springframework.web.filter.DelegatingFilterProxy.invokeDelegate(DelegatingFilterProxy.java:344)
    at org.springframework.web.filter.DelegatingFilterProxy.doFilter(DelegatingFilterProxy.java:261)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:239)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:219)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:106)
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:502)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:142)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:79)
    at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:610)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:88)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:518)
    at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1091)
    at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:668)
    at org.apache.coyote.http11.Http11NioProtocol$Http11ConnectionHandler.process(Http11NioProtocol.java:223)
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1517)
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.run(NioEndpoint.java:1474)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
    at java.lang.Thread.run(Thread.java:745)
Caused by: java.lang.ClassCastException: [Ljava.lang.Object; cannot be cast to app1.domain.App1User
    at app1.persistance.UserManageDAOImpl.findUserByName(UserManageDAOImpl.java:102)
    at app1.web.authentification.UserDetailsServiceImpl.loadUserByUsername(UserDetailsServiceImpl.java:36)
    at org.springframework.security.authentication.dao.DaoAuthenticationProvider.retrieveUser(DaoAuthenticationProvider.java:114)
    ... 42 more

And also my UserDetailServiceImpl class:

public UserDetails loadUserByUsername(String userName) 
                                                throws UsernameNotFoundException {


        App1User listUser = userManageDAOIF.findUserByName(userName);
        String password = null;
        Collection<GrantedAuthority> authorities = null;

        if(listUser != null) {

                password = (String)listUser.getPassword();

                authorities = new ArrayList<GrantedAuthority>();

                    authorities.add(new SimpleGrantedAuthority("ROLE_USER"));


                org.springframework.security.core.userdetails.User secureUser = new
                        org.springframework.security.core.userdetails.User(userName, password, authorities);

                return secureUser;

        } else {

            throw new UsernameNotFoundException("No user exist in datbase");
        }

    }

Answer 1

When you select specific columns from DB, the result you get is not the entity object, but an Object[] , with each element of array holding different column values. So, what you're getting from query.list() method is: List<Object[]> . So, certainly when you cast list.get(0) , to App1User , that will result in ClassCastException .

So, either you get the Object[] and build the App1User entity object like this:

// size of this array would be number of columns in select query
Object[] attr = listUser.get(0);
App1User appUser = new App1User(attr[0], attr[1], attr[2], ...);

Certainly not the best way. Better approach is to get a List<App1User> from db. For that just change the query from:

String stringSQL = "select au.userId, au.firstName, au.lastName, au.middleName, au.username, au.password, au.userPosition from App1User au where au.username = :userNameArg";

to:

String stringSQL = "select au from App1User au where au.username = :userNameArg";