反射注解的方式

package 反射与注解;

import jdk.management.resource.internal.inst.SocketOutputStreamRMHooks;

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

public class 反射注解 {
    public static void main(String[] args) throws ClassNotFoundException, NoSuchFieldException {
        Class<?> c1 = Class.forName("反射与注解.Student");
        Annotation[] declaredAnnotations = c1.getDeclaredAnnotations();

        //获得类注解
        for (Annotation declaredAnnotation : declaredAnnotations) {
            System.out.println(declaredAnnotation);
        }

        // 获取value的值
        dbChris annotation = c1.getAnnotation(dbChris.class);
        System.out.println(annotation.value());


        //获取指定列的注解
        Field age = c1.getDeclaredField("age");
        columnChris annotation1 = age.getAnnotation(columnChris.class);
        System.out.println(annotation1.colName());
        System.out.println(annotation1.type());
        System.out.println(annotation1.length());

    }
}


@dbChris("tStudent")
class Student {
    @columnChris(colName = "dId", type = "int", length = 10)
    private int id;
    @columnChris(colName = "dAge", type = "int", length = 10)
    private int age;
    @columnChris(colName = "dName", type = "varchar", length = 20)
    private String name;

    public int getId() {
        return id;
    }

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

    public int getAge() {
        return age;
    }

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

    public String getName() {
        return name;
    }

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

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

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


@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@interface dbChris {
    String value();
}

@Target(ElementType.FIELD)
@Retention(RetentionPolicy.RUNTIME)
@interface columnChris {
    String colName();

    String type();

    int length() default 10;
}

输出结果