Object Oriented Language has very powerful feature of Polymorphism, it is used to remove if/else or switch case in code.
Code without condition is easy to read. There are some places where you have to put them and one of such example is Factory/ServiceProvider class.
I am sure you have seen factory class with IF-ELSEIF which keeps on getting big.
In this blog i will share some techniques that you can be used to remove condition in factory class.
I will use below code snippet as example
Reflection
This is first thing that comes to mind when you want to remove conditions. You get the feeling of framework developer!
This looks very simple but only problem is caller has to remember fully qualified class name and some time it could be issue.
Map
Map can be used to to map actual class instance to some user friendly name
This also looks neat without overhead of reflection.
Enum
This is interesting one
This method is using enum method to remove condition, one of the issue is that you need Enum for each type. You don't want to create tons of them!
I personally like this method.
Conclusion
If-else or switch case makes code difficult to understand, we should try to avoid them as much as possible. Language construct should be used to avoid some of switch case.
We should try to code without IF-ELSE and that will force us to come up with better solution.
This is first thing that comes to mind when you want to remove conditions. You get the feeling of framework developer!
This looks very simple but only problem is caller has to remember fully qualified class name and some time it could be issue.
Map
Map can be used to to map actual class instance to some user friendly name
This also looks neat without overhead of reflection.
Enum
This is interesting one
This method is using enum method to remove condition, one of the issue is that you need Enum for each type. You don't want to create tons of them!
I personally like this method.
Conclusion
If-else or switch case makes code difficult to understand, we should try to avoid them as much as possible. Language construct should be used to avoid some of switch case.
We should try to code without IF-ELSE and that will force us to come up with better solution.
I think Java Service Loader would be a good option.
ReplyDeleteCode will be something like this...
ReplyDeletepublic T getService(final Class clazz) {
ServiceLoader serviceLoader = ServiceLoader.load(clazz);
final Iterator iter = serviceLoader.iterator();
Object impl = null;
while (iter.hasNext()) {
impl = iter.next();
}
return (T) impl;
}