java反射之Field 獲取對象屬性及設置屬性值

首先先創建一個User

    private String  name;

    private Integer age;

    private Double  height;

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public Integer getAge() {
        return age;
    }

    public void setAge(Integer age) {
        this.age = age;
    }

    public Double getHeight() {
        return height;
    }

    public void setHeight(Double height) {
        this.height = height;
    }

假設現在獲取name這個屬性，並同時給這個User取名爲張三

public static void main(String[] args) {
        User user1 = new User();
        try {
            Field field = User.class.getDeclaredField("name");
            
            //setAccessible這行代碼把對象上的name字段設置爲public訪問屬性.
            field.setAccessible(true);
            
            // 設置該user1的name屬性
            field.set(user1, "zhangsan");
            System.out.println(user.getName());
        } catch (Exception e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }

在這裏能看見

   field.setAccessible(true);

這行代碼，setAccessible的作用是將Field對象上的指定字段訪問值設置爲public，

可以看上面User類，該類下的所有屬性都是private的訪問權限，如果將setAccessible註釋掉，系統將給出

IllegalAccessException: Class test_field.TestField can not access a member of class test_field.User with modifiers "private"