public class SessionAttributesHandler {

    private final Set<String> attributeNames = new HashSet<String>();

    private final Set<Class<?>> attributeTypes = new HashSet<Class<?>>();

    private final Set<String> knownAttributeNames = Collections.synchronizedSet(new
 
 HashSet<String>(4));

    private final SessionAttributeStore sessionAttributeStore;

    public SessionAttributesHandler(Class<?> handlerType, SessionAttributeStore sessionAttributeStore) {
        Assert.notNull(sessionAttributeStore, "SessionAttributeStore may not be null.");
        
 
this.sessionAttributeStore = sessionAttributeStore;

        SessionAttributes annotation = AnnotationUtils.findAnnotation(handlerType, SessionAttributes.class);
        if (annotation != null) {
            this.attributeNames.addAll(Arrays.asList(annotation.value()));
            this.attributeTypes.addAll(Arrays.<Class<?>>asList(annotation.types()));
        }

        
 
this.knownAttributeNames.addAll(this.attributeNames);
    }


    public boolean hasSessionAttributes() {
        return ((this.attributeNames.size() > 0) || (this.attributeTypes.size() > 0));
    }


    public boolean isHandlerSessionAttribute(String attributeName, Class<?> attributeType) {
        Assert.notNull(attributeName, "Attribute name must not be null");
        if (this.attributeNames.contains(attributeName) || this.attributeTypes.contains(attributeType)) {
            this.knownAttributeNames.add(attributeName);
            return true;
        }
        else {
            return false;
        }
    }


    public void storeAttributes(WebRequest request, Map<String, ?> attributes) {
        for (String name : attributes.keySet()) {
            Object value = attributes.get(name);
            Class<?> attrType = (value != null) ? value.getClass() : null;

            if (isHandlerSessionAttribute(name, attrType)) {
                this.sessionAttributeStore.storeAttribute(request, name, value);
            }
        }
    }

    public Map<String, Object> retrieveAttributes(WebRequest request) {
        Map<String, Object> attributes = new HashMap<String, Object>();
        for (String name : this.knownAttributeNames) {
            Object value = this.sessionAttributeStore.retrieveAttribute(request, name);
            if (value != null) {
                attributes.put(name, value);
            }
        }
        return attributes;
    }


    public void cleanupAttributes(WebRequest request) {
        for (String attributeName : this.knownAttributeNames) {
            this.sessionAttributeStore.cleanupAttribute(request, attributeName);
        }
    }


    Object retrieveAttribute(WebRequest request, String attributeName) {
        return this.sessionAttributeStore.retrieveAttribute(request, attributeName);
    }

}