注解与反射-蒲公英云

注解与反射

package com.company;
import java.lang.annotation.*;
import java.lang.reflect.Field;
public class test3 { 
    public static void main(String[] args) throws ClassNotFoundException, NoSuchFieldException { 
        Class c1 = Class.forName("com.company.Student2");
        //通过反射获得注解
        Annotation[] annotations = c1.getAnnotations();
        for (Annotation annotation:annotations){ 
            System.out.println(annotation);
        }
        //获得注解的value的植
        annon annotations1 = (annon) c1.getAnnotation(annon.class);
        String value = annotations1.value();
        System.out.println(value);
        //获得id类指定的注解
        Field id = c1.getDeclaredField("id");
        bnnon annotation = id.getAnnotation(bnnon.class);
        System.out.println(annotation.columnName());
        System.out.println(annotation.type());
        System.out.println(annotation.length());
        Field age = c1.getDeclaredField("age");
        bnnon annotationage = age.getAnnotation(bnnon.class);
        System.out.println(annotationage.columnName());
        System.out.println(annotationage.type());
        System.out.println(annotationage.length());
        Field name = c1.getDeclaredField("age");
        bnnon annotationagename = name.getAnnotation(bnnon.class);
        System.out.println(annotationagename.columnName());
        System.out.println(annotationagename.type());
        System.out.println(annotationagename.length());
    }
}
@annon("biaoming")
class Student2{ 
    @bnnon(columnName = "db_id",type = "int",length = "1")
    private int id;
    @bnnon(columnName = "db_age",type = "int",length = "3")
    private int age;
    @bnnon(columnName = "db_name",type = "String",length = "4")
    private String name;
    public Student2(int id, int age, String name) { 
        this.id = id;
        this.age = age;
        this.name = name;
    }
    public Student2() { 
    }
    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;
    }
    @Override
    public String toString() { 
        return "Student2{" +
                "id=" + id +
                ", age=" + age +
                ", name='" + name + '\'' +
                '}';
    }
}
@Target({ ElementType.TYPE,ElementType.METHOD})
@Retention(RetentionPolicy.RUNTIME)
@interface annon{ 
    String value();
}
@Target({ ElementType.FIELD})
@Retention(RetentionPolicy.RUNTIME)
@interface bnnon{ 
    String columnName();
    String type();
    String length();
}