Fixing BeanNotOfRequiredTypeException on Spring proxy cast on a non-singleton bean?

Question

I'm having an issue with pulling a Spring bean from an application context.

When I try;

InnerThread instance = (InnerThread) SpringContextFactory.getApplicationContext().getBean("innerThread", InnerThread.class);

I get;

org.springframework.beans.factory.BeanNotOfRequiredTypeException: Bean named 'innerThread' must be of type [com.generic.InnerThread], but was actually of type [$Proxy26]

Without the specified class in the getBean() call I get a ClassCastException (which you can see in detail below).

The InnerThread bean is being initialized as a non-singleton, because I need multiple instances. The InnerThread class also extends Thread. The interesting thing is that this error shows up within OuterThread, which is set up in the exact same way the InnerThread is.

I've tried to include all relevant code listings/stack traces below. Could someone with more Spring experience tell me what is going on here?

---

Code/Configuration Listing

OuterThread.java snippet:

public class OuterThread extends Thread {
    private Queue<InnerThread> createInnerThreads() {
     Queue<InnerThread> threads = new ArrayBlockingQueue();

     ApplicationContext ctx = SpringContextFactory.getApplicationContext();
     int i = 0;
     for (SearchRule search : searches) {
      logger.debug("Number of times looped " + i++);
      //Seprated lines to get a better sense of what is going on
      Object proxy = ctx.getBean("innerThread", InnerThread.class);
      logger.debug(ReflectionToStringBuilder.toString(proxy));
      logger.debug("proxy.getClass(): " + proxy.getClass());
      logger.debug("proxy.getClass().getClassLoader(): " + proxy.getClass().getClassLoader());
      logger.debug("proxy.getClass().getDeclaringClass(): " + proxy.getClass().getDeclaringClass());
      logger.debug("InnerThread.class.getClassLoader(): " + InnerThread.class.getClassLoader());

      //---Exception here---
      InnerThread cst = (InnerThread) proxy;

      threads.add(cst);
     }
     return threads;
    }

    public static void main(String[] args) throws Exception {
     try {
      OuterThread instance = (OuterThread) SpringContextFactory.getApplicationContext().getBean("outerThread", OuterThread.class);
      instance.run();
     } catch (Exception ex) {
      logger.error("Fatal exception.", ex);
      throw ex;
     }
    }
}

SpringContextFactory.java:

public class SpringContextFactory {
    static final Logger logger = LoggerFactory.getLogger(SpringContextFactory.class);
    private static ApplicationContext ctx;
    private static final String DEFAULT_PATH = "META-INF/app-context.xml";

    public static ApplicationContext getApplicationContext() {
        return getApplicationContext(DEFAULT_PATH);
    }

    public static synchronized ApplicationContext getApplicationContext(String path) {
        if (ctx == null) return createApplicationContext(path);
        else return ctx;
    }

    private static ApplicationContext createApplicationContext(String path) {
        if (logger.isDebugEnabled()) logger.debug("Loading Spring Context...");
        ctx = new ClassPathXmlApplicationContext(path);
        if (logger.isDebugEnabled()) logger.debug("Spring Context Loaded");
        return ctx;
    }
}

app-context.xml:

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns:context="http://www.springframework.org/schema/context"
       xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-2.5.xsd"&gt;

    <!-- persistence context from separate jar -->
    <import resource="persistence-context.xml"/>

    <bean id="outerThread" class="com.generic.OuterThread" scope="prototype"/>
    <bean id="innerThread" class="com.generic.InnerThread" scope="prototype"/>

</beans>

Stack Trace

2009-05-08 14:34:37,341 [main] DEBUG com.generic.OuterThread.init(OuterThread.java:59) - Initializing OuterThread object, com.generic.OuterThread@1c8fb4b[em=org.hibernate.ejb.EntityManagerImpl@e2892b,currentTime=java.util.GregorianCalendar[time=1241634874841,areFieldsSet=true,areAllFieldsSet=true,lenient=true,zone=sun.util.calendar.ZoneInfo[id="America/New_York",offset=-18000000,dstSavings=3600000,useDaylight=true,transitions=235,lastRule=java.util.SimpleTimeZone[id=America/New_York,offset=-18000000,dstSavings=3600000,useDaylight=true,startYear=0,startMode=3,startMonth=2,startDay=8,startDayOfWeek=1,startTime=7200000,startTimeMode=0,endMode=3,endMonth=10,endDay=1,endDayOfWeek=1,endTime=7200000,endTimeMode=0]],firstDayOfWeek=1,minimalDaysInFirstWeek=1,ERA=1,YEAR=2009,MONTH=4,WEEK_OF_YEAR=19,WEEK_OF_MONTH=2,DAY_OF_MONTH=6,DAY_OF_YEAR=126,DAY_OF_WEEK=4,DAY_OF_WEEK_IN_MONTH=1,AM_PM=1,HOUR=2,HOUR_OF_DAY=14,MINUTE=34,SECOND=34,MILLISECOND=841,ZONE_OFFSET=-18000000,DST_OFFSET=3600000],maxConcurrentThreads=5,reconId=3,reportUsername=TEST,useOffset=false,username=removed,uuid=bf61494d-ff96-431c-a41f-1e292d0c9fbe,name={T,h,r,e,a,d,-,1},priority=5,threadQ=<null>,eetop=0,single_step=false,daemon=false,stillborn=false,target=<null>,group=java.lang.ThreadGroup[name=main,maxpri=10],contextClassLoader=sun.misc.Launcher$AppClassLoader@11b86e7,inheritedAccessControlContext=java.security.AccessControlContext@1524d43,threadLocals=<null>,inheritableThreadLocals=java.lang.ThreadLocal$ThreadLocalMap@2cbc86,stackSize=0,nativeParkEventPointer=0,tid=9,threadStatus=0,parkBlocker=<null>,blocker=<null>,blockerLock=java.lang.Object@a68fd8,stopBeforeStart=false,throwableFromStop=<null>,uncaughtExceptionHandler=<null>]
2009-05-08 14:34:37,341 [main] DEBUG org.springframework.orm.jpa.ExtendedEntityManagerCreator$ExtendedEntityManagerInvocationHandler.doJoinTransaction(ExtendedEntityManagerCreator.java:385) - No local transaction to join
2009-05-08 14:34:37,529 [main] DEBUG com.generic.OuterThread.createInnerThreads(OuterThread.java:139) - Number of times looped 0
2009-05-08 14:34:37,529 [main] DEBUG org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory$1.run(AbstractAutowireCapableBeanFactory.java:458) - Creating instance of bean 'searchThread' with merged definition [Root bean: class [com.generic.InnerThread]; scope=prototype; abstract=false; lazyInit=false; autowireCandidate=true; autowireMode=0; dependencyCheck=0; factoryBeanName=null; factoryMethodName=null; initMethodName=null; destroyMethodName=null; defined in class path resource [META-INF/app-context.xml]]
2009-05-08 14:34:37,545 [main] DEBUG com.generic.InnerThread.<init>(InnerThread.java:50) - Constructing InnerThread object, com.generic.InnerThread@1080876[em=<null>,coolScheme=<null>,coolUrl=<null>,date=<null>,error=<null>,millisecondsTaken=0,thresholdMet=false,reconId=0,result=-2,searchId=0,username=<null>,uuid=<null>,name={T,h,r,e,a,d,-,2},priority=5,threadQ=<null>,eetop=0,single_step=false,daemon=false,stillborn=false,target=<null>,group=java.lang.ThreadGroup[name=main,maxpri=10],contextClassLoader=sun.misc.Launcher$AppClassLoader@11b86e7,inheritedAccessControlContext=java.security.AccessControlContext@1524d43,threadLocals=<null>,inheritableThreadLocals=java.lang.ThreadLocal$ThreadLocalMap@3aef16,stackSize=0,nativeParkEventPointer=0,tid=10,threadStatus=0,parkBlocker=<null>,blocker=<null>,blockerLock=java.lang.Object@126c6ea,stopBeforeStart=false,throwableFromStop=<null>,uncaughtExceptionHandler=<null>]
2009-05-08 14:34:37,545 [main] DEBUG org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:203) - Returning cached instance of singleton bean 'entityManagerFactory'
2009-05-08 14:34:37,545 [main] DEBUG org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:203) - Returning cached instance of singleton bean 'org.springframework.transaction.config.internalTransactionAdvisor'
2009-05-08 14:34:37,560 [main] DEBUG org.springframework.transaction.interceptor.AbstractFallbackTransactionAttributeSource.getTransactionAttribute(AbstractFallbackTransactionAttributeSource.java:108) - Adding transactional method [report] with attribute [PROPAGATION_REQUIRED,ISOLATION_DEFAULT]
2009-05-08 14:34:37,560 [main] DEBUG org.springframework.aop.framework.autoproxy.AbstractAutoProxyCreator.buildAdvisors(AbstractAutoProxyCreator.java:494) - Creating implicit proxy for bean 'searchThread' with 0 common interceptors and 1 specific interceptors
2009-05-08 14:34:37,560 [main] DEBUG org.springframework.aop.framework.JdkDynamicAopProxy.getProxy(JdkDynamicAopProxy.java:113) - Creating JDK dynamic proxy: target source is SingletonTargetSource for target object [com.generic.InnerThread@1080876]
2009-05-08 14:34:37,591 [main] DEBUG com.generic.OuterThread.createInnerThreads(OuterThread.java:141) - $Proxy26@1594a88[h=org.springframework.aop.framework.JdkDynamicAopProxy@1f0cf51]
2009-05-08 14:34:37,591 [main] DEBUG com.generic.OuterThread.createInnerThreads(OuterThread.java:142) - proxy.getClass(): class $Proxy26
2009-05-08 14:34:37,591 [main] DEBUG com.generic.OuterThread.createInnerThreads(OuterThread.java:143) - proxy.getClass().getClassLoader(): sun.misc.Launcher$AppClassLoader@11b86e7
2009-05-08 14:34:37,591 [main] DEBUG com.generic.OuterThread.createInnerThreads(OuterThread.java:144) - proxy.getClass().getDeclaringClass(): null
2009-05-08 14:34:37,591 [main] DEBUG com.generic.OuterThread.createInnerThreads(OuterThread.java:145) - InnerThread.class.getClassLoader(): sun.misc.Launcher$AppClassLoader@11b86e7
2009-05-08 14:34:37,591 [main] ERROR com.generic.OuterThread.run(OuterThread.java:101) - Exception in OuterThread, ending reconciliation.
java.lang.ClassCastException: $Proxy26 cannot be cast to com.generic.InnerThread
    at com.generic.OuterThread.createInnerThreads(OuterThread.java:148)
    at com.generic.OuterThread.run(OuterThread.java:65)
    at com.generic.OuterThread.main(OuterThread.java:170)

---

Similar questions that do not answer my question

• Auto-cast Spring Beans
• ClassCastException when casting to the same class.

Answer 1

This is just a guess, but try making an interface InnerThreadInterface, then let InnerThread class extend it.

After that you should be able to do:

InnerThreadInterface inner = ctx.getBean("innerThread", InnerThread.class);

Answer 2

Once again, after spending hours trying to debug this I find the answer right after posting on StackOverflow.

A key point that I left out from my question is that InnerThread has a transactional method (sorry thought this was irrelevant). This is the important difference between OuterThread and InnerThread.

From the Spring documentation:

Note

Multiple sections are collapsed into a single unified auto-proxy creator at runtime, which applies the strongest proxy settings that any of the sections (typically from different XML bean definition files) specified. This also applies to the and elements.

To be clear: using 'proxy-target-class="true"' on , or elements will force the use of CGLIB proxies for all three of them.

Adding the above to my configuration (based in persistance-context.xml, which you can see loaded above) line seems to fix the problem. However, I think this may be a quick fix workaround as opposed to real solution.

I think I've got a few deeper issues here, number one being that I find Spring as confusing as expletive deleted. Second I should probably be using Spring's TaskExecutor to kick off my threads. Third my threads should implement Runnable instead of extending Thread (See SO question below).

See Also

• BeanNotOfRequiredTypeException using ServiceLocatorFactoryBean and @Transactional (Nothing better then finding a thread off Google after hours of searching to have a response that says "This has already been answered a million times.")
• Section 6.6 in the Spring Docs.
• Java: “implements Runnable” vs. “extends Thread”

Answer 3

I had this issue even though I referenced CGLIB and used the proxy-target-class="true" setting. I determined ehcache:annotation tag was to blame... Removing the following configuration solved this for me. Fortunately, I was able to use hibernate level 2 caching instead of having to use ehcache declarative caching.

<ehcache:annotations>
 <ehcache:caching id="myCacheModel" cacheName="myCache"/>
 <ehcache:flushing id="myFlushModel" cacheNames="myCache" when="after"/>
</ehcache:annotations>

Answer 4

Another way to handle this problem would be to implement an interface and request the interface from spring, the proxy would fully implement the interface, and the cast shouldn't have a problem.