Question

I am trying to write a framework where plugins can be dynamically loaded. One step in this loading process is to load in a properties file “properties.plugin” I would like to load this into a PropertyPlaceholderConfigurer however it appears that this uses a different Classloader than the one the GenericApplicationContext has been set to use.

My code for creating the context:

GenericApplicationContext ctx = new GenericApplicationContext();
    if(classLoader !=null)
        ctx.setClassLoader(classLoader);
    ctx.getDefaultListableBeanFactory().setAllowBeanDefinitionOverriding(false);

    XmlBeanDefinitionReader xmlReader = new XmlBeanDefinitionReader(ctx);
    xmlReader.setBeanClassLoader(classLoader);
    int totalBeanCount = 0;
    List<Resource> processedResources = new ArrayList<Resource>(resources.length);
    for(Resource r:resources)
    {
        try
        {
            int loadedBeanCount = xmlReader.loadBeanDefinitions(r);
            totalBeanCount += loadedBeanCount;
            processedResources.add(r);

        }
        catch(BeanDefinitionStoreException e)
        {

            throw e;
        }
    }

classLoader in the above code gets set at start up.

The bean is setup as follows:

<bean name="ReloadedPropertiesPlaceholderConfigurer" class="myProject.MyPropertyPlaceholderConfigurer" >
    <property name="locationNames" ref="locationNamesList" />
    <property name="ignoreUnresolvablePlaceholders" value="true"/>
</bean>

<bean name="locationNamesList" class="java.util.ArrayList">
    <constructor-arg>
        <list>
            <value>properties/properties.plugin</value>
        </list>
    </constructor-arg>
</bean>

myProject.MyPropertyPlaceholderConfigurer simply extends PropertyPlaceholderConfigurer

When I call ctx.refresh() later in the code i see a log message saying could not find properties/properties.plugin

The following code

classLoader.getResource("properties/properties.plugin");

Works if i add it just before setting the class loader on the context.

I have also tried classpath:properties/properties.plugin, properties.plugin, classpath*:properties.plugin.

Is it the case that this PropertyPlaceholderConfigurer is using a different classloader than the one set on ctx and if so is there a way to set the class loader it uses?

I don’t see a setClassLoader method.

Answer 1

 Thread.currentThread().setContextClassLoader(classLoader);

Seems to make it work so it must be using this class loader instead of the one set on the context.