getAnnotations

getAnnotation

以後的框架大量的通過註解讀取資訊

package com.zhou.reflection;

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

public class Test07 {
    public static void main(String[] args) throws NoSuchFieldException {
        Class c1 = Comment.class;
        //通過反射獲得註解
        Annotation[] annotations = c1.getAnnotations();
        for (Annotation annotation : annotations) {
            System.out.println(annotation);
        }

        //通過反射獲取value值
        TableZhou annotation = (TableZhou) c1.getAnnotation(TableZhou.class);
        System.out.println(annotation.value());

        //獲取指定屬性的註解
        Field name = c1.getDeclaredField("name");
        FieldZhou annotation1 = name.getAnnotation(FieldZhou.class);
        System.out.println(annotation1.columnName());
        System.out.println(annotation1.length());
        System.out.println(annotation1.type());

    }
}

@TableZhou("db")
class Comment {
    @FieldZhou(columnName = "db_id", type = "int", length = 10)
    private int id;
    @FieldZhou(columnName = "db_age", type = "int", length = 3)
    private int age;
    @FieldZhou(columnName = "db_name", type = "varchar", length = 5)
    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 Comment() {
    }

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

//類註解
@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@interface TableZhou {
    String value();
}

//屬性註解
@Target(ElementType.FIELD)
@Retention(RetentionPolicy.RUNTIME)
@interface FieldZhou {
    String columnName();

    String type();

    int length();
}