Architecting in Java(!): Planning for Exception

There has always been confusion and debates on what to do with “exception” and how to use it. Now, if you see “exception handling” in context of just a programming practice, or java, or a convention, you are sure to get challenged by both your team members and yourself. During my early years, I have been in turmoil for making right decisions on it. But over the time, I have learned lessons and found the real purpose of exceptions which I am gonna share today:

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Spring multiple configuration classes: Loading beans, components, repositories, configurations from other packages

In the beginning, I had a hundred problems creating beans, and spent hours to understand how spring works. I produce a lot of modules and libraries and separate everything by features. So, my applications don’t have a simple model-view-controller folder-set as I have hundreds or even thousands of classes in enterprise solutions. And, I was facing issues with setting up my libraries which were not in the application package in spring. By application package I mean where the Spring Application class resides in and all the sub-packages.

So, what happens when packages are outside? – the beans are not created, the spring annotations do not work! The solution is pretty easy but hard to find unless you are already familiar with “spring keywords“. But, the only way to get familiar with spring terminology is to become a master of it first! Anyway, so my goal here is to write tutorials which would be easy to find with common keywords like “my beans are not working in spring”.

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Implement Lucene Search in Android App – How to make it work

I created an Android app for World Health Organization long ago. I made different kinds of search engines before with full-text indexing. This time I wanted to do something different. I had only 4 days to make the app. They had different kinds of contents like

  1. html
  2. Plain text files
  3. PDF files

And they needed a search engine to search all the contents and show a unified result set ( Showing results in a same page with relevancy ). Now I could implement it in SQLite, but that would mean a lot of task and the gain would be much lesser than a document-based search engine like Apache Lucene.

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Springboot and MongoDB: Creating indices on inherited properties or fields.

I started writing my first spring and the first springboot application today. The project requires mongodb and mysql as databases. My application’s domain objects are highly hierarchical and we need to make different kinds of search engines for many child classes. So, there needs to be some violations from common patterns like “field shadowing”. Though it’s only for the purpose of data and search layer, it doesn’t affect the object model of the application. So, I needed to change field behavior in subclasses which are different entities or collections in Mongo store. Basically I needed to put a annotation on subclass to enable an index on a field.

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Writing Effective “Special Case Pattern” and “Null Object Pattern”

Handling null can be problematic in code organization and management. So, there are two very common patterns used by experienced developers now and then. One is “Null object pattern”, where you return an object which states a missing object, and another is “Special Case Pattern”. This article is to “How you can write effective objects for those patterns and why you should use them instead of returning null or throwing exceptions”

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Associative Array in Java like PHP?

I don’t know how many times I saw this question asked by many PHP developers. It happens when some developer is not developing in Java actively, need to do some quick codes, and does PHP development regularly. Associative arrays are one of the most used feature (or is it the most?) of PHP.

Though collections are basic java features, and why many of PHP developers cannot readily catch that they can use Maps or Properties collections? It’s mainly because of OOP pattern. Java collections are objects. And many PHP developers are too accustomed to using Non-OOP patterns even if they are coding in a object oriented framework like laravel, or symfony, or zend.