Using Cookies with Servant Locators
Occasionally, it can be useful for a servant locator to pass information between locate and finished. For example, the implementation of locate could choose among a number of alternative database backends, depending on load or availability and, to properly finalize state, the implementation of finished might need to know which database was used by locate. To support such scenarios, you can create a cookie in your locate implementation; the Ice run time passes the value of the cookie to finished after the operation invocation has completed. The cookie must derive from Ice::LocalObject and can contain whatever state and member functions are useful to your implementation:
class MyCookie
{
public:
// Whatever is useful here...
};
class MyServantLocator : public Ice::ServantLocator
{
public:
virtual std::shared_ptr<Ice::Object> locate(const Ice::Current& current, std::shared_ptr<void>& cookie) override
{
// Code as before...
// Allocate and initialize a cookie.
//
cookie = std::make_shared<MyCookie>(...);
return std::make_shared<PhoneEntryI>();
}
virtual void finished(const Ice::Current& current, const std::shared_ptr<Ice::Object>& servant, const std::shared_ptr<void>& cookie) override
{
// Down-cast cookie to actual type.
//
auto mc = std::static_pointer_cast<MyCookie>(cookie);
// Use information in cookie to clean up...
//
// ...
}
virtual void deactivate(const std::string& category) override
{
}
};
class MyCookie : public Ice::LocalObject
{
public:
// Whatever is useful here...
};
typedef IceUtil::Handle<MyCookie> MyCookiePtr;
class MyServantLocator : public Ice::ServantLocator
{
public:
virtual Ice::ObjectPtr locate(const Ice::Current& current, Ice::LocalObjectPtr& cookie)
{
// Code as before...
// Allocate and initialize a cookie.
//
cookie = new MyCookie(...);
return new PhoneEntryI;
}
virtual void finished(const Ice::Current& current, const Ice::ObjectPtr& servant, const Ice::LocalObjectPtr& cookie)
{
// Down-cast cookie to actual type.
//
MyCookiePtr mc = MyCookiePtr::dynamicCast(cookie);
// Use information in cookie to clean up...
//
// ...
}
virtual void deactivate(const std::string& category)
{
}
};