Simple case of reflection operation annotation

package Reflection;

import java.lang.annotation.*;
import java.lang.reflect.Field;

//练习反射操作注解
public class Test11 {
    
    
    public static void main(String[] args) throws ClassNotFoundException, NoSuchFieldException {
    
    
        Class c1 = Class.forName("Reflection.Student2");

        //通过反射获得注解
        Annotation[]  annotation = c1.getAnnotations();
        for (Annotation annotation1 : annotation) {
    
    
            System.out.println(annotation1);
        }

        //获得注解Value的值
        SSS s = (SSS)c1.getAnnotation(SSS.class);
        String value = s.value();
        System.out.println(value);


        //获得类指定的注解
        Field id = c1.getDeclaredField("id");
        Fields an = id.getAnnotation(Fields.class);
        System.out.println(an.columnName());
        System.out.println(an.type());
        System.out.println(an.length());

    }

}

@SSS("db_student")
class Student2{
    
    
    @Fields(columnName = "db_id",type = "int",length = 10)
    private int id;
    @Fields(columnName = "db_name",type = "varchar",length = 3)
    private String name;
    @Fields(columnName = "db_age",type = "int",length = 10)
    private int age;

    public Student2() {
    
    
    }

    public Student2(int id, String name, int age) {
    
    
        this.id = id;
        this.name = name;
        this.age = age;
    }

    public int getId() {
    
    
        return id;
    }

    public void setId(int id) {
    
    
        this.id = id;
    }

    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;
    }

    @Override
    public String toString() {
    
    
        return "Student{" +
                "id=" + id +
                ", name='" + name + '\'' +
                ", age=" + age +
                '}';
    }
}


//类名的注解
@Target(ElementType.TYPE)   //作用在什么地方
@Retention(RetentionPolicy.RUNTIME)     //什么级别获取
@interface  SSS{
    
    
    String value();
}

//属性的注解
@Target(ElementType.FIELD)   //作用在什么地方
@Retention(RetentionPolicy.RUNTIME)  //什么级别获取
@interface Fields{
    
    
    String columnName();
    String type();
    int length();
}