[Springframework-developer] ApplicationContext custom classloader problems

[Rich G. <ric...@sr...>]

Hi all,

org.springframework.core.io.DefaultResourceLoader has the method 
"setClassLoader" to set the class loader used to load resources. I have 
a FileSystemXmlApplicationContext and I set the class loader on it 
before the context refreshes.

The problem is that certain default beans always use the thread context 
class loader even when they are specified in the XML file loaded with my 
FileSystemXmlApplicationContext. For example, here are 2 bean 
declarations which fail to use the class loader I specified:

<bean id="rexaService" 
class="org.springframework.remoting.caucho.HessianProxyFactoryBean">
    <property name="serviceUrl" 
value="http://localhost:8081/RexaRetrieval"/>
    <property name="serviceInterface" 
value="com.sri.iris.plugins.rexa.IDataRetrievalAgent"/>
</bean>

and

<bean 
class="org.springframework.beans.factory.config.FieldRetrievingFactoryBean" 
autowire="no" dependency-check="none">
    <property name="staticField" 
value="com.sri.iris.store.pojo.IFormDefinitionPojo.SUMMARY_VIEW_IS"/>
</bean>

These fail if the class name given only resides in the custom class 
loader and not the thread context class loader.

A workaround is to set the thread context class loader to the 
DefaultResourceLoader's class loader using a BeanPostProcessor (the 
"postProcessBeforeInitialization" method). For example:
        public Object postProcessBeforeInitialization(Object bean, 
String beanName) throws BeansException {
            // XXX Make sure the ClassLoader of the ApplicationContext 
is set as the thread context class loader...
            boolean clSet = false;
            if (applicationContext instanceof DefaultResourceLoader) {
                ClassLoader cl = 
((DefaultResourceLoader)applicationContext).getClassLoader();
                if (cl != null) {
                    Thread.currentThread().setContextClassLoader(cl);
                    clSet = true;
                }
            }
            if (!clSet) {
                
Thread.currentThread().setContextClassLoader(bean.getClass().getClassLoader());
            }
This workaround fixes the problem and the above bean definitions can 
find classes in the custom class loader..

My main question is: should this be supported in Spring? It seems to be 
an ambiguity because Spring allows the class laoder to be set, but then 
doesn't set it to the thread context class loader before initializing beans.

Thanks,
Rich