哪位高手能解释下SpringFactory里每个方法具体的作用

package com.base;import flex.messaging.*;import flex.messaging.config.ConfigMap;import flex.messaging.services.ServiceException;import javax.servlet.ServletConfig;import org.springframework.beans.BeansException;import org.springframework.beans.factory.NoSuchBeanDefinitionException;import org.springframework.context.ApplicationContext;import org.springframework.web.context.support.WebApplicationContextUtils;public class SpringFactory implements FlexFactory {    static class SpringFactoryInstance extends FactoryInstance {        public String toString() {            return (new StringBuilder("SpringFactory instance for id="))                    .append(getId()).append(" source=").append(getSource())                    .append(" scope=").append(getScope()).toString();        }        public Object lookup() {            ApplicationContext appContext;            String beanName;            appContext = WebApplicationContextUtils                    .getWebApplicationContext(FlexContext.getServletConfig()                            .getServletContext());            beanName = getSource();            return appContext.getBean(beanName);        }        SpringFactoryInstance(SpringFactory factory, String id,                ConfigMap properties) {            super(factory, id, properties);        }    }    private static final String SOURCE = "source";    public SpringFactory() {    }    public void initialize(String s, ConfigMap configmap) {    }    public FactoryInstance createFactoryInstance(String id, ConfigMap properties) {        SpringFactoryInstance instance = new SpringFactoryInstance(this, id,                properties);        instance.setSource(properties.getPropertyAsString("source", instance                .getId()));        return instance;    }    public Object lookup(FactoryInstance inst) {        SpringFactoryInstance factoryInstance = (SpringFactoryInstance) inst;        return factoryInstance.lookup();    }}