Java – How do we freeze an object while constructing an object using JavaBeans pattern

If you insist of having your object to immutable, there is obviously no other way than providing the 20 strings through the constructor. And if you want to be able to leave some of the strings out, you must say which arguments you are providing and which are not, which leads you to some form of named parameters. Of course, besides the possibilities you mentioned by yourself, you can also

• provide the 20 arguments by a list of strings
• provide them by a dictionary (key=>value, where "key" is the attribute name)
• provide them by an object of a helper class, which has the same 20 properties with getters and setters, so this one won't be immutable

It may also be a good idea to implement Equals and GetHashCodeby utilizing reflection, looping over all public string properties of your class.

Your concerns are very much valid and they tell me your original easy caching solution is eventually becoming part of your architecture which naturally brings a new level of issues as you described yourself.

A good architectural solution to caching is to use annotations combined with IoC which solves several problems you described. For example:

• Allow you to better control the life-cycle of your cached objects
• Allow you to replace the caching behavior easily by changing the annotations (instead of changing the implementation)
• Let you easily configure a multi-layered cache where you could be storing in memory then disk cache for example
• Let you define the key (hash) for each method in the annotation itself

In my projects (Java or C#) I use Spring caching annotations. You can find a brief description here.

IoC is a key concept in this solution because it allows you to configure your caching system anyway you want.

In order to implement a similar solution in Python you have to find how to use annotations and search for a IoC container that allows you to build proxies. That's how the annotations work in order to intercept all method calls and provide you this particular solution for caching.