Java之反射機制一：獲取及其操做類的屬性

1.實體類

public class Dog {
    private String color;

    public boolean hasTail;

    public boolean isHasTail() {
        return hasTail;
    }

    public void setHasTail(boolean hasTail) {
        this.hasTail = hasTail;
    }

    public String getColor() {
        return color;
    }

    public void setColor(String color) {
        this.color = color;
    }

    @Override
    public String toString() {
        return "Dog{" +
                "color='" + color + '\'' +
                '}';
    }
}

2.經過java反射機制獲取類的屬性的值

@Test
public void test1(){
    Dog dog = new Dog();
    dog.setColor("白");
    Class clazz = dog.getClass();
    try {
        Field color = clazz.getDeclaredField("color");
        //設置即便該屬性是private，也能夠進行訪問(默認是false)
        color.setAccessible(true);
        String c = color.get(dog).toString();
        System.out.println(dog);
    }catch (Exception e){
        e.printStackTrace();
    }
}

運行結果:

 

3.經過java反射機制設置類的屬性

@Test
    public void test2(){
        Dog dog = new Dog();
        Class clazz = dog.getClass();
        try{
            Field color = clazz.getDeclaredField("color");
            color.setAccessible(true);
            color.set(dog,"黑");
            System.out.println(dog);
        }catch (Exception e){
            e.printStackTrace();
        }

    }

　運行結果:

 4.getField方法和getDeclaredField方法二者區別(getFields和getDeclaredFields同理)

getField：只能獲取類和其父類的public屬性

getDeclaredField：該方法只能夠獲取類自己的屬性（private public protected default）,但不包括父類

實體類BigDog.java繼承於Dog.java

public class BigDog extends Dog {
    private Integer age;

    public String name;

    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;
    }

    @Override
    public String toString() {
        return "BigDog{" +
                "age=" + age +
                '}';
    }
}

測試getFields方法：

@Test
    public void test(){
        BigDog dog  = new BigDog();
        Class dogClass = dog.getClass();
        //只能獲取類及其父類的公有屬性
        Field[] fields = dogClass.getFields();
        for (Field field : fields) {
            System.out.println(field);
        }
    }

　運行截圖：

 測試getDeclaredFields方法：

@Test
    public void test3(){
        BigDog dog  = new BigDog();
        Class dogClass = dog.getClass();
        //能獲取該類中全部的屬性，可是不能獲取父類的屬性
        Field[] fields = dogClass.getDeclaredFields();
        for (Field field : fields) {
            System.out.println(field);
        }
    }

運行截圖：