All this information is processed using java reflection capability. ORMs like hibernate use the config files (not they use annotations) for defining the relationship between entities and relationship between entity and database schemas. Parsing annotations by ORMs like hibernate entity Annotations are analyzed for dependencies injection using reflection only. Spring 3 onwards, you can define the dependencies using annotations as well, using autowiring. DI framework actually heavily uses reflection for injecting these bean dependencies. Spring framework uses dependency injection (DI) to populate the dependencies into beans defined in config files. The same is valid for unmarshaling as well. They look up all annotated attributes in java bean, analyze their overall attributes and generate XML tags for them. JAXB/Jattison and other marshalling/unmarshaling libraries heavily use reflection for XML (or JSON) to/from java beans code. In fact, reflection is heavily used in plugins for these kind of IDEs be it eclipse, or IntelliJ or any other IDE for that matter.
#Java reflection use case code
And almost 90% of the logic for code generation was written around reflection only. Return value was a JAXB annotated class which was also generated by plugin. It used to create one REST API per interface method, and using wizard you can specify the other REST specific things such as HTTP method (GET, PUT, POST, DELETE), query parameters, path parameters and return values. I have worked in a team which developed an eclipse plugin for generating REST API sourcecode, for methods defined in some interfaces. Clearly, they use reflection to this analysis.Įclipse (Other IDEs) auto completion of method namesĮver stressed your mind, how eclipse is able to provide you method suggestions whenever you hit CTRL+SPACE, even when you are not finished with writing that class. How can they do it without looking inside the class. They are written in a way such that they can analyze any class file passed to them to analyze. They do static analysis of syntax, show optimization tips and even report error conditions, and many more such things. Having talked about need of reflection in real life application programming, it’s time to list down some instances where reflection is used to accomplish certain objectives.Ĭode analyzers tools do lots of different things with your code. Generally, It is said that whenever you don’t know, at compile time, the type that should be instantiated or the method that should invoked, you will need reflection. You can accomplish any task, fulfill any requirement without reflection when you know the classes you are going to use.īut as soon as, you are told to deal with classes which you don’t know at time of writing the code, and you must write code in too general way such that it can handle any class type then you will need reflection to do the job.įor example, you are told to write a code analyzer which is able to look inside any class and list down it’s all private method then you can do this only by reflection. In practical, if you know the classes you are dealing with in your application, you may never ever come across a situation where you will need reflection. Java is strongly typed language with all the “good” features of OOPs. Having said that in one sentence, let me elaborate it further.
#Java reflection use case professional
More than a few professional programmers would answer “ as rarely as possible, maybe even never.” Example uses of reflection for impatients Code analyzer tools Eclipse auto completion of method names Marshalling and unmarshalling Spring Framework for creating the beans Parsing annotations by ORMs like hibernate entity Junit Testcases When somebody would need Reflection? real life practical examples of reflection in java. I promised to come up with my leanings/thoughts on this specific topic, and so here in this post, I will discuss the same i.e. This immediately back-fired me with lots of requests to come up with some real life “good” examples of reflection, and possible scenarios where a developer will be needing it. In my previous tutorial, I discussed basics of annotation in which I discussed the usage of reflection to read the applied annotations on a class or a method. Reflection is one of those things like multi-threading where everyone with experience of it says “Don’t use it unless you absolutely have to”.Ībove quote is absolutely true for all for us alike.
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