Java: Convenient way to refactor the application

We have an agile enterprise application built on JSP and Servlet without any design strategy.

This application was built in early 2002 considering 1000 users. After 2002, we received lots of requests from the marketing partners.

Currently, the application has lots of spaghetti code with lots of Ifs and elses. One class has more than 20,000 lines of code with a huge body of functions without abstraction.

Now, we need to support billions of records, what we need to do immediately and gradually?

We have to refactor the application? Which framework, we need to use? How the usage of the framework will be helpful 开发者_Go百科to the end users? How to convince the leaders to do the refactoring? How to gain the faster response time as compare to the current system?

Here is how I would approach this if I had appropriate company resources at my disposal (yeah right):

1. Get a good QA process going, with automated regression testing set up before making significant changes. I don't care how good you are, you can't put a system like that under unit test and reasonably control for regressions.
2. Map out interdependencies, see how much an individual class can be tested as a unit.
3. How do you eat an elephant? One bite at a time. Take a given piece of required functionality (preferably something around the increase load requirements) and refactor the parts of the class or classes that can be worked on in isolation.
4. Learn how do 3 above by reading Working Effectively with Legacy Code.

Convenient way to refactor the application.

There are no "convenient" or "easy" ways to refactor an existing codebase, especially if the codebase looks like spaghetti.

... what we need to do immediately and gradually?

That's impossible to answer without understanding your system's current architecture.

We have to refactor the application?

On the one hand, the fact that you have a lot of poorly designed / maintained code would suggest that it needs some refactoring work.

However, it is not clear that it will be sufficient. It could be that a complete rewrite would be a better idea ... especially if you need to scale up by many orders of magnitude.

Which framework, we need to use?

Impossible to answer without details for your application.

How the usage of the framework will be helpful to the end users?

It might reduce response times. It might improve reliability. It might allow more online users simultaneously. It might do none of the above.

Using a framework won't magically fix a problem of bad design.

How to convince the leaders to do the refactoring?

You need to convince them that the project is going to give a good return on investment (ROV). You / they also need to consider the alternatives:

• what happens if you / they do nothing, or
• is a complete rewrite likely to give a better outcome.

How to gain the faster response time as compare to the current system?

Impossible to answer without understanding why the current system is slow.

The bottom line is that you probably need someone from outside your immediate group (e.g. an external consultant) to do a detailed review your current system and report on your options for fixing it. It sounds like your management don't trust your recommendations.

These are big, big questions. Too broad for one answer really.

My best advice is this: start small, if you can. Refactor piece by piece. And most importantly, before touching the code, write automated tests against the current codebase, so you can be relatively sure you haven't broken anything when you do refactor it.

It may not be possible to write these tests, as the code may not be testable in it's current format. But you should still make this one of your main goals.

By definition refactoring shouldn't show any difference to the users. It's only to help developers work on the code. It sounds like you want to do a more extensive rewrite to modernize the application. Moving to something like JSF will make life a lot easier for developers and will give you access to web component libraries to improve the user experience.

It is a question which needs a lengthy answer. To start with I would suggest that the application is tested well and is working as per the specification. This means there are enough unit, integration and functional tests. The functional tests also have to be automated. Once these are in place, a step by step refactoring can take place. Do you have enough tests to start?