springboot@注解/小白简单理解

最新推荐文章于 2025-12-18 13:32:52 发布

原创最新推荐文章于 2025-12-18 13:32:52 发布 · 219 阅读

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本文通过一个Java示例程序介绍了枚举类型和注解的使用方法。演示了如何定义枚举类型限制变量的取值，并展示了如何创建自定义注解及通过反射读取这些注解信息。

@Service 在这里插入图片描述
枚举：
让某个类型的变量只能取若干固定值中的一个，不然编译器会报错。可以控制源程序在编译期的赋值的非法不非法。

public enum Color {
    RED,YELLO,GREEN
}

@Retention(RetentionPolicy.RUNTIME)   //运行时有用
public @interface MyAnnotation {
    public String name(); //定义变量,定义完变量后一定要给值。
    public int age() default 2; //给了默认值为2
    public String[] like();   //数组
    public Color color();     //枚举

}

 @Test
    public void t2() throws InstantiationException, IllegalAccessException {
        //反射处理注解
        Class<Cat> catClass = Cat.class;
        MyAnnotation annotation = catClass.getAnnotation(MyAnnotation.class);
        int age = annotation.age();
        Color color = annotation.color();
        String[] like = annotation.like();
        String name = annotation.name();
        Cat cat = catClass.newInstance();
        cat.setAge(age);
        cat.setColor(color);
        cat.setName(name);
        cat.setLike(like);
        System.out.println(cat);
    }

@MyAnnotation(name="bilibili",like = {"fish","beef"},color = Color.GREEN)
public class Cat {
    private String name;
    private int age;
    private String[] like;
    private Color color;

    @Override
    public String toString() {
        return "Cat{" +
                "name='" + name + '\'' +
                ", age=" + age +
                ", like=" + Arrays.toString(like) +
                ", color=" + color +
                '}';
    }

    public String getName() {
        return name;
    }

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

    public int getAge() {
        return age;
    }

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

    public String[] getLike() {
        return like;
    }

    public void setLike(String[] like) {
        this.like = like;
    }

    public Color getColor() {
        return color;
    }

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

    @Deprecated
    public String pringinf() {
        return "Cat{" +
                "name='" + name + '\'' +
                ", age=" + age +
                ", like=" + Arrays.toString(like) +
                ", color=" + color +
                '}';
    }

    public Cat() {
    }

    public Cat(String name, int age, String[] like, Color color) {
        this.name = name;
        this.age = age;
        this.like = like;
        this.color = color;
    }
}