Master Java Reflection: 5 Essential Techniques for Dynamic Code

Java reflection is a powerful feature widely used by frameworks such as Spring and MyBatis for dependency injection, dynamic proxies, and other core functionalities.

Reflection enables a program to obtain class information (name, constructors, methods, fields) and to create objects or invoke methods at runtime.

Below are five common reflection operations with complete code examples.

1. Invoke a method without parameters

// Get Class object
Class<?> clazz = Class.forName("com.mikechen.MyClass");

// Invoke no‑arg method
Method method1 = clazz.getDeclaredMethod("testMethod1");
Object result1 = method1.invoke(clazz.newInstance());
System.out.println(result1);

2. Invoke a method with parameters

// Get Class object
Class<?> clazz = Class.forName("com.mikechen.MyClass");

// Invoke method with a String argument
Method method2 = clazz.getDeclaredMethod("testMethod2", String.class);
Object result2 = method2.invoke(clazz.newInstance(), "Hello World");
System.out.println(result2);

3. Invoke a static method

First obtain the Class object, then retrieve the static method and invoke it with null as the instance.

Class<?> clazz = Class.forName("com.mikechen.MyClass");
Method method = clazz.getMethod("myStaticMethod", String.class, int.class);
Object result = method.invoke(null, "Hello", 123);

4. Invoke a private method

Use getDeclaredMethod and setAccessible(true) to bypass access checks.

Method method = clazz.getDeclaredMethod("myPrivateMethod", String.class);
method.setAccessible(true);
method.invoke(obj, "John");

5. Invoke a superclass method

Obtain the superclass Class object, then retrieve and invoke the desired method.

Class<?> superClass = clazz.getSuperclass();
Method method = superClass.getDeclaredMethod("parentMethod");
method.invoke(obj);