How can I make Spring load classes from a given URL (for bean instantiation)?

Question

Is there a way to tell Spring to load classes from a given URL while instantiating the beans? I need to load classes from a location that is not in the classpath. If I were using pure Java, I could use URLClassLoader but how can I achieve this in Spring? I am using Spring 3.0

Answer 1

All Spring classes that extend DefaultResourceLoader can have an explicit ClassLoader reference set (via DefaultResourceLoader.setClassLoader(ClassLoader).

AbstractApplicationContext happens to be one of those classes. So all ApplicationContext implementations that extend it (like ClassPathXmlApplicationContext and FileSystemXmlApplicationContext) can use an injected ClassLoader reference.

Answer 2

public class Main {

    public static void main(String[] args) throws Exception {  
        AnnotationConfigApplicationContext ctx = new AnnotationConfigApplicationContext(AutodeployConfiguration.class);

        URL[] files = {
            new File("C:\\module1.jar").toURL(),
            new File("C:\\propertiesdirectory\\").toURL()
        };

        URLClassLoader plugin = new URLClassLoader(files, Main.class.getClassLoader());
        Thread.currentThread().setContextClassLoader(plugin);

        Class startclass = plugin.loadClass("de.module1.YourModule");
        ExternalModule start = (ExternalModule) startclass.newInstance();
        AnnotationConfigApplicationContext ivr = start.onDeploy(plugin, ctx);
    }
}


public class YourModule implements ExternalModule {

    @Override
    public AnnotationConfigApplicationContext onDeploy(ClassLoader classloader, GenericApplicationContext parent) {      
        AnnotationConfigApplicationContext applicationContext = new AnnotationConfigApplicationContext();
        applicationContext.setClassLoader(classloader);
        applicationContext.setParent(parent);
        applicationContext.register(ModuleConcreteConfiguration.class);
        applicationContext.refresh();


        // other code

        return applicationContext;
    }
}