关于反射与自定义注解的一些使用

Posted 2021-03-16 yrjns

 

对实体类的属性进行校验，等处理。

 

自定义注解

import java.lang.annotation.Documented;
import java.lang.annotation.ElementType;
import java.lang.annotation.Inherited;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.FIELD)
@Documented
@Inherited
public @interface OrderAnnotation {

    int length();

    int sort();

}

实体类

public class Merchandise {

    @OrderAnnotation(sort=1,length=10)
    private String id;

    @OrderAnnotation(sort=2,length=50)
    private String name;

    @OrderAnnotation(sort=3,length=100)
    private String desc;

    ... getset 方法和toString 方法

}

 

import java.beans.IntrospectionException;
import java.beans.PropertyDescriptor;
import java.lang.reflect.Field;
import java.lang.reflect.Method;

import org.springframework.util.ReflectionUtils;

public class Main {

    public static void main(String[] args) throws IntrospectionException, IllegalArgumentException, IllegalAccessException {
        Merchandise merchandise = new Merchandise();
        merchandise.setId("11");
        merchandise.setName("sanye");
        merchandise.setDesc("descdesc...中");
        re(merchandise);
        System.out.println(merchandise.toString());
    }

    public static void re(Object o) throws IntrospectionException, IllegalArgumentException, IllegalAccessException{
        Class c = o.getClass();
        Field[] fields = c.getDeclaredFields();
        for (Field field : fields) {
            // 得到注解
            if(field.isAnnotationPresent(OrderAnnotation.class)) {
                OrderAnnotation orderAnnotation = field.getAnnotation(OrderAnnotation.class);
                int sort = orderAnnotation.sort();
                int length = orderAnnotation.length();
                System.out.println("顺序："+sort+"   长度："+length);

            }

            //获取字段值
            PropertyDescriptor pd = new PropertyDescriptor(field.getName(), c);
            Method getMethod = pd.getReadMethod();
            Object valueObj = ReflectionUtils.invokeMethod(getMethod, o);//执行方法
            System.out.println(field.getName() + "  "+String.valueOf(valueObj));

            //设置字段值
            field.setAccessible(true);
            field.set(o, "aaaaaaaaa");
            field.setAccessible(false);

        }

    }

}

 

结果：

顺序：1   长度：10
id  11
顺序：2   长度：50
name  sanye
顺序：3   长度：100
desc  descdesc...中
Merchandise [id=aaaaaaaaa, name=aaaaaaaaa, desc=aaaaaaaaa]