「Java/reflection」の版間の差分

2019年6月18日 (火) 18:00時点における版

reflectionとは

privateのプロパティやメソッドにアクセスする

reflectionサンプル

通常アクセス

Animal.java
public class Animal {
    public String name = "animal";
    public int foot = 4;
    public int getFoot() {
        return foot;
    }
}

main.java

Animal animal = new Animal();
Log.i(TAG, "name=" + animal.name); // animal
Log.i(TAG, "foot=" + animal.foot); // 4
Log.i(TAG, "getFoot=" + animal.getFoot()); // 4

reflectionでprivateプロパティアクセス

Animal.java

public class Animal {
    private String name = "animal";
    private int foot = 4;
}

main.java

Animal animal = new Animal();
Class animalClass = animal.getClass();
Field nameField = animalClass.getDeclaredField("name");
Field footField = animalClass.getDeclaredField("foot");
nameField.setAccessible(true);
footField.setAccessible(true);
Log.i(TAG, "nameField=" + (String)nameField.get(animal)); // animal
Log.i(TAG, "footField=" + (int)footField.get(animal)); // 4

Animal.java

public class Animal {
    private String name = "animal";
    private int foot = 4;
    private int getFoot() {
        return foot;
    }
}

main.java

Animal animal = new Animal();
Class animalClass = animal.getClass();
Method method = animalClass.getDeclaredMethod("getFoot");
method.setAccessible(true);
Log.i(TAG, "getFootField=" +  (int)method.invoke(animal)); // 4

参考：https://qiita.com/ohke/items/b096c5cb9d2932764f22