The concept of Java Reflection API has been discussed here in the presentation. Some code snippets have also been introduces to illustrate the different interfaces and use cases. http://bd.linkedin.com/in/imranhasanhira https://www.facebook.com/KonaSoftware https://www.linkedin.com/company/kona-software-lab-ltd-

1. Java Reflection API
@KonaTechAdda
Md Imran Hasan Hira
Software Engineer
Kona Software Lab Ltd.
http://bd.linkedin.com/in/imranhasanhira
https://www.facebook.com/KonaSoftware
https://www.linkedin.com/company/kona-software-lab-ltd-

2. Outlines
• Design of reflection API
• Getting class
• Encoding class names
• Examples
• Modifiers
• Drawbacks
What & Why
• Logics vs configurations
• Dependency Injections
• Methods param suggestion
• Build tools
• Spring…
• Runtime Code generation
• Bytecode Manipulation

3. Java Reflection
JavaObject

4. Basic Idea
• Accessing a field in runtime
• Find a class
• Instantiate a object form the class
• Find it’s field
• Set value of the field on that object
• Calling a method in runtime
• Find a class
• Instantiate a object form the class
• Find it’s method
• Invoke the method (with/without parameter)
• Get the returned value

5. Necessary Classes
java.lang.Class
java.lang.reflection.Method
java.lang.reflection.Field
java.lang.reflection.Constructor
java.lang.reflection.Modifier
java.lang.reflection.Parameter

6. “Class” ক্লাশের public methods
Class
Including private
Including Inherited
Own + private, no inherited
Own + inherited, except private

7. “Constructor” & “Method”
Constructor
Method

8. “Field” & “Modifier”
Field
Modifier

9. Ways to get class
1. With the static field*
2. Providing full class path
3. getClass() method

10. Classpath encoding schema*
byte
char
MyClass
MyClass[]
byte[]
“B”
“C”
“Lcom.mypackage.MyClass;”
“[Lcom.myPackage.MyClass;”
“[B”
byte[][] “[[B”

11. Finding fields upto superclass
new Manager();

12. Data Parsing

13. Data Parsing (Dynamic)

14. Method Calling
Name: Default name, Age: 0
Name: Dynamic name, Age: 0

15. JavaObject

16. Reflection Drawbacks
• Performance overhead
• Dynamically type resolutions occlude JVM optimizations.
• Should be avoided in parts of code in performance sensitive applications
*Taken from a article of Dennis Sosnoski,

17. Reflection Drawbacks
• Performance overhead
• Dynamically type resolutions occlude JVM optimizations.
• Should be avoided in parts of code in performance sensitive applications
• Security Restrictions
• Requires a runtime permission, so your code may not run in a restricted
security context.
• Exposure of Internals
• Accessing private fields and methods
• Reflective code breaks abstractions*

18. References
Article from Oracle -
https://docs.oracle.com/javase/tutorial/reflect/
http://docs.oracle.com/javase/8/docs/api/index.html?java/lang/Class.
html
Dennis Sosnoski’s Article on Reflection -
http://www.ibm.com/developerworks/java/library/j-
dyn0603/index.html
Source Code Snippets -
https://github.com/imranhasanhira/java-reflection-annotation-test

19. Thank You 