public Class getCommonPropertyType(ELContext context,
    Object base) 
{
        if (base == null) {
            return String.class;
        }
        return null;
}

If the base object is null, returns String.class. Otherwise, returns null.

 public Iterator getFeatureDescriptors(ELContext context,
    Object base) 
{
        Enumeration attrs;
        ArrayList< FeatureDescriptor > list = new ArrayList< FeatureDescriptor >();
        PageContext ctxt = (PageContext) context.getContext(JspContext.class);
        attrs = ctxt.getAttributeNamesInScope(PageContext.PAGE_SCOPE);
        while (attrs.hasMoreElements()) {
            String name = (String) attrs.nextElement();
            Object value = ctxt.getAttribute(name, PageContext.PAGE_SCOPE);
            FeatureDescriptor descriptor = new FeatureDescriptor();
            descriptor.setName(name);
            descriptor.setDisplayName(name);
            descriptor.setShortDescription("page scope attribute");
            descriptor.setExpert(false);
            descriptor.setHidden(false);
            descriptor.setPreferred(true);
            descriptor.setValue("type", value.getClass());
            descriptor.setValue("resolvableAtDesignTime", Boolean.TRUE);
            list.add(descriptor);
        }
        attrs = ctxt.getAttributeNamesInScope(PageContext.REQUEST_SCOPE);
        while (attrs.hasMoreElements()) {
            String name = (String) attrs.nextElement();
            Object value = ctxt.getAttribute(name, PageContext.REQUEST_SCOPE);
            FeatureDescriptor descriptor = new FeatureDescriptor();
            descriptor.setName(name);
            descriptor.setDisplayName(name);
            descriptor.setShortDescription("request scope attribute");
            descriptor.setExpert(false);
            descriptor.setHidden(false);
            descriptor.setPreferred(true);
            descriptor.setValue("type", value.getClass());
            descriptor.setValue("resolvableAtDesignTime", Boolean.TRUE);
            list.add(descriptor);
        }
        attrs = ctxt.getAttributeNamesInScope(PageContext.SESSION_SCOPE);
        while (attrs.hasMoreElements()) {
            String name = (String) attrs.nextElement();
            Object value = ctxt.getAttribute(name, PageContext.SESSION_SCOPE);
            FeatureDescriptor descriptor = new FeatureDescriptor();
            descriptor.setName(name);
            descriptor.setDisplayName(name);
            descriptor.setShortDescription("session scope attribute");
            descriptor.setExpert(false);
            descriptor.setHidden(false);
            descriptor.setPreferred(true);
            descriptor.setValue("type", value.getClass());
            descriptor.setValue("resolvableAtDesignTime", Boolean.TRUE);
            list.add(descriptor);
        }
        attrs = ctxt.getAttributeNamesInScope(PageContext.APPLICATION_SCOPE);
        while (attrs.hasMoreElements()) {
            String name = (String) attrs.nextElement();
            Object value = ctxt.getAttribute(name, PageContext.APPLICATION_SCOPE);
            FeatureDescriptor descriptor = new FeatureDescriptor();
            descriptor.setName(name);
            descriptor.setDisplayName(name);
            descriptor.setShortDescription("application scope attribute");
            descriptor.setExpert(false);
            descriptor.setHidden(false);
            descriptor.setPreferred(true);
            descriptor.setValue("type", value.getClass());
            descriptor.setValue("resolvableAtDesignTime", Boolean.TRUE);
            list.add(descriptor);
        }
        return list.iterator();
}

If the base object is null, returns an Iterator containing FeatureDescriptor objects with information about each scoped attribute resolved by this resolver. Otherwise, returns null.

The Iterator returned must contain one instance of java.beans.FeatureDescriptor for each scoped attribute found in any scope. Each info object contains information about a single scoped attribute, and is initialized as follows:

displayName - The name of the scoped attribute.

name - Same as displayName property.

shortDescription - A suitable description for the scoped attribute. Should include the attribute's current scope (page, request, session, application). Will vary by implementation.

expert - false

hidden - false

preferred - true

In addition, the following named attributes must be set in the returned FeatureDescriptors:

ELResolver#TYPE - The current runtime type of the scoped attribute.

ELResolver#RESOLVABLE_AT_DESIGN_TIME - true.

 public Class getType(ELContext context,
    Object base,
    Object property) 
{
        if (context == null) {
            throw new NullPointerException();
        }
        if (base == null) {
            context.setPropertyResolved(true);
            return Object.class;
        }
        return null;
}

If the base object is null, returns Object.class to indicate that any type is valid to set for a scoped attribute.

The propertyResolved property of the ELContext object must be set to true by this resolver before returning if base is null. If this property is not true after this method is called, the caller should ignore the return value.

 public Object getValue(ELContext context,
    Object base,
    Object property) 
{
        if (context == null) {
            throw new NullPointerException();
        }
        if (base == null) {
            context.setPropertyResolved(true);
            if (property instanceof String) {
                String attribute = (String) property;
                PageContext ctxt = (PageContext)
                                       context.getContext(JspContext.class);
                return ctxt.findAttribute(attribute);
            }
        }
        return null;
}

If the base object is null, searches the page, request, session and application scopes for an attribute with the given name and returns it, or null if no attribute exists with the current name.

The propertyResolved property of the ELContext object must be set to true by this resolver before returning if base is null. If this property is not true after this method is called, the caller should ignore the return value.

 public boolean isReadOnly(ELContext context,
    Object base,
    Object property) 
{
        if (context == null) {
            throw new NullPointerException();
        }
        if (base == null) {
            context.setPropertyResolved(true);
        }
        return false;
}

If the base object is null, returns false to indicate that scoped attributes are never read-only.

The propertyResolved property of the ELContext object must be set to true by this resolver before returning if base is null. If this property is not true after this method is called, the caller should ignore the return value.

 public  void setValue(ELContext context,
    Object base,
    Object property,
    Object val) 
{
        if (context == null) {
            throw new NullPointerException();
        }
        if (base == null) {
            context.setPropertyResolved(true);
            if (property instanceof String) {
                PageContext ctxt = (PageContext)
                                       context.getContext(JspContext.class);
                String attr = (String) property;
                if (ctxt.getAttribute(attr, PageContext.REQUEST_SCOPE) != null)
                    ctxt.setAttribute(attr, val, PageContext.REQUEST_SCOPE);
                else if (ctxt.getAttribute(attr, PageContext.SESSION_SCOPE) != null)
                    ctxt.setAttribute(attr, val, PageContext.SESSION_SCOPE);
                else if (ctxt.getAttribute(attr, PageContext.APPLICATION_SCOPE) != null)
                    ctxt.setAttribute(attr, val, PageContext.APPLICATION_SCOPE);
                else {
                    ctxt.setAttribute(attr, val, PageContext.PAGE_SCOPE);
                }
            }
        }
}

If the base object is null, sets an existing scoped attribute to the new value, or creates a new scoped attribute if one does not exist by this name.

If the provided attribute name matches the key of an attribute in page scope, request scope, session scope, or application scope, the corresponding attribute value will be replaced by the provided value. Otherwise, a new page scope attribute will be created with the given name and value.

The propertyResolved property of the ELContext object must be set to true by this resolver before returning if base is null. If this property is not true after this method is called, the caller should ignore the return value.