![Example:
// without reflection
Foo foo = new Foo();
foo.hello();
// with reflection
Object foo = Class.forName("complete.classpath.and.Foo").newInstance();
// Alternatively: Object foo = Foo.class.newInstance();
Method m = foo.getClass().getDeclaredMethod("hello", new Class<?>[0]);
m.invoke(foo);](https://image.slidesharecdn.com/javareflection-160527104206/85/Java-reflection-4-320.jpg)
Java reflection
- 2. Agenda What is Reflection? How to get the object Class class Reflection vs Metaprogramming Why do we need reflection? Demo Real Usage Examples
- 3. What is Reflection? Reflection is used for observing and modifying program execution at runtime. A reflection-oriented program component can monitor the execution of an enclosure of code and can modify itself according to a desired goal related to that enclosure. 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”.
- 4. Example: // without reflection Foo foo = new Foo(); foo.hello(); // with reflection Object foo = Class.forName("complete.classpath.and.Foo").newInstance(); // Alternatively: Object foo = Foo.class.newInstance(); Method m = foo.getClass().getDeclaredMethod("hello", new Class<?>[0]); m.invoke(foo);
- 5. How to get the object of Class class forName() method of Class class Class c=Class.forName("Simple") System.out.println(c.getName()) getClass() method of Object class Class c=obj.getClass(); System.out.println(c.getName()); the .class syntax Class c2 = Test.class; System.out.println(c2.getName());
- 6. Reflection vs Metaprogramming Metaprogramming is "programs which write programs". This includes programs that read the text of programs (arguably including themselves but that is rather rare), analyze that code, and make changes. Reflection is the ability for a program to inquire about its own structure.
- 7. Why do we need reflection? Examine an object’s class at runtime Construct an object for a class at runtime Examine a class’s field and method at runtime Invoke any method of an object at runtime
- 8. Demo
- 9. Real Usage Example Code analyzer tools Eclipse (Other IDEs) auto completion of method names Spring Framework for creating the beans Parsing annotations by ORMs like hibernate entity
- 10. Somewhere I read this quote: “When you will need reflection; you will know it”.
- 11. For live project example https://github.com/NexThoughts/ReflectionDemo
- 13. Thanks You