![]() ![]() 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. 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. You can find complete code on this Github Repository and please feel free to provide your valuable feedback.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. Class.newInstance() throws any exception (checked or unchecked) thrown by the constructor, Constructor.newInstance() always wraps the thrown exception with an InvocationTargetException.ĭue to above reasons Constructor.newInstance() is preferred over Class.newInstance(), that’s why used by various frameworks and APIs like Spring, Guava, Zookeeper, Jackson, Servlet etc. ![]() Class.newInstance() requires that the constructor should be visible, Constructor.newInstance() can also invoke private constructors under certain circumstances. Class.newInstance() can only invoke the no-arg constructor, Constructor.newInstance() can invoke any constructor, regardless of the number of parameters. It internally use class to get the object, which is Oracle's private API.ĭifference between Class.newInstance() and Constructor.newInstance()īy name, both methods look same but there are differences between them which we are as following 1. In order to use Constructor.newInstance() method we first need to get constructor object for that class and then we can call newInstance() on it to create objects as shown below Constructor constructor = () Įmployee emp3 = constructor.newInstance() Or Employee emp = (Employee) Class.forName(".Employee").newInstance() Class.newInstance() internally itself use the Constructor.newInstance() to create the object as we can see in the source code of Class class, notice line no 430 and 442 in below image. class to it and another is using Class.forName() method, So in below code Employee.class is similar to (Employee) Class.forName(".Employee")īelow code demonstrates how we can create objects using Class.newInstance() Employee emp = () We can do this by two ways one is writing complete name of the class and appending. In order to use Class.newInstance() we first need to get the class level instance of that class for which we want to create objects. However, this class lies in the java.lang package but plays a major role in Reflection API ( .* package). The Class class is the most popular class in Java after the Object class. ![]() Both are not static and we can call earlier one on a class level object while latter one needs constructor level object which we can get by using the class level object. However there are total 5 ways create objects in Java, if you are not aware of them please go through this article 5 Different ways to create objects in Java with Example.īoth Class.newInstance() and .newInstance() are known as reflective methods because these two uses reflection API to create the object.
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