Java Reflection - Getters and Setters

Jakob Jenkov
Last update: 2024-01-18

Using Java Reflection you can inspect the methods of classes and invoke them at runtime. This can be used to detect what getters and setters a given Java class has. You cannot ask for getters and setters explicitly, so you will have to scan through all the methods of a class and check if each method is a getter or setter yourself - by checking if the method signature matches what you would expect from a getter or setter.

First let's establish the rules that characterizes getters and setters:

Getter
A getter method have its name start with "get", take 0 parameters, and returns a value.
Setter
A setter method have its name start with "set", and takes 1 parameter.

Setters may or may not return a value. Some setters return void, some the value set, others the object the setter were called on for use in method chaining. Therefore you should make no assumptions about the return type of a setter.

Here is a code example that finds getter and setters of a class:

public static void printGettersSetters(Class aClass){
  Method[] methods = aClass.getMethods();

  for(Method method : methods){
    if(isGetter(method)) System.out.println("getter: " + method);
    if(isSetter(method)) System.out.println("setter: " + method);
  }
}

public static boolean isGetter(Method method){
  if(!method.getName().startsWith("get"))      return false;
  if(method.getParameterTypes().length != 0)   return false;  
  if(void.class.equals(method.getReturnType()) return false;
  return true;
}

public static boolean isSetter(Method method){
  if(!method.getName().startsWith("set")) return false;
  if(method.getParameterTypes().length != 1) return false;
  return true;
}

Next: Java Reflection - Private Fields and Methods

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	Jakob Jenkov