Java Reflection API Tutorial

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This is a complete beginner to expert in-depth Java Reflection API Tutorial. Reflection is commonly used by programs which require the ability to examine or modify the runtime behavior of applications running in the Java virtual machine. This is a relatively advanced feature and should be used only by developers who have a strong grasp of the fundamentals of the language.

Check out java.lang.reflect package on Java Lang Reflect Package Tutorial

The source code examples of this tutorial are well tested with our local development environment and you can use these code examples as bug-free. The complete core java reference guide available on Core Java Guide.

>> Overview of Java Reflection API

>> Java Reflection for Classes

In this article, we will discuss Java Class and it's methods which entry point for all the reflection operations For every type of object, JVM instantiates an immutable instance of java.lang.Class that provides methods to examine the runtime properties of the object and create new objects, invoke its method and get/set object fields.

• Get Class Object
• Get Super Class
• Get Public Member Classes
• Get Declared Classes
• Get Declaring Class
• Getting Package Name
• Getting Class Modifiers
• Get Type Parameters
• Get Implemented Interfaces
• Get All Public Methods
• Get All Public Constructors
• Get All Public Fields
• Get All Annotations

>> Java Reflection for Methods

The java.lang.reflect.Method class provides APIs to access information about a method's modifiers, return type, parameters, annotations, and thrown exceptions. It also is used to invoke methods.

• Obtaining Method Type Information
• Obtaining Names of Method Parameters
• Retrieving and Parsing Method Modifiers
• Get Public Method
• Invoking Public Method
• Get All Public Methods

>> Java Reflection for Fields

Reflection API provides several methods to analyze Class fields and modify their values at runtime, in this guide, we will look into some of the commonly used reflection functions for methods.

• Get All Public Fields
• Get Public Field
• Field Declaring Class
• Get Field Type
• Get/Set Public Field Value
• Get/Set Private Field Value

>> Java Reflection for Constructors

A Constructor is used in the creation of an object that is an instance of a class. Typically it performs operations required to initialize the class before methods are invoked or fields are accessed. Constructors are never inherited.

• Finding Constructors
• Retrieving and Parsing Constructor Modifiers
• Creating New Class Instances
• Get Constructor
• Get Constructor Information

>> Java Reflection for Arrays

This article describes how to determine if a class member is a field of array type, illustrates how to create new instances of arrays with simple and complex component types and shows how to access fields of type array and individually access array elements with examples.

• Identifying Array-Types
• Creating New Arrays
• Getting and Setting Arrays and Their Components

>> Java Reflection for Enums 

In this article, we will discuss how to use Class and java.lang.reflect.Field with enums with examples.

• Examining Enums
• Getting and Setting Fields with Enum Types 

Java Reflection Utilities

1. Top Reflection Utility Methods
2. Java Reflection Utility Class 

GitHub Repository

1. https://github.com/RameshMF/java-reflection-guide