java 用反射获取自定义注解的信息实例

最近看了些spring的源码，回来重新看一下反射和注解的一些文档，写了一个小例子，记录一下。
package com.wbk.annotation;

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

public class ReflectionAndAnnotation {
    public static void main(String[] args) throws ClassNotFoundException {

        //获得类的class对象
        Class c1 = Class.forName("com.wbk.annotation.user");

        //获得class对象的注解列表
        Annotation[] annotations = c1.getAnnotations();

        //打印类注解信息
        for (Annotation annotation : annotations) {
            System.out.println("注解列表:"+annotation);
        }
        //获得class的特定注解信息
        Annotation annotation = c1.getAnnotation(table_name.class);
        System.out.println("user的类注解："+annotation);

        System.out.println("==========================================================");

        //获得class对象的属性列表
        Field[] declaredFields = c1.getDeclaredFields();
        for (Field declaredField : declaredFields) {
            //获得属性的注解列表
            Annotation[] annotations1 = declaredField.getAnnotations();
            for (Annotation annotation1 : annotations1) {
                //属性注解列表信息打印
                System.out.println(declaredField.getName()+":"+annotation1);
            }
        }
    }
}

/**
 * 要映射的user对象，加入自定的类注解和属性注解
 */
@table_name("db_user")
class user {

    @field_data(column="user_id",type = "varchar",length = 10)
    private int id;
    @field_data(column="user_age",type = "varchar",length = 10)
    private  int age;
    @field_data(column="user_name",type = "varchar",length = 10)
    private String name;


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

    public String getName() {
        return name;
    }

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

@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
/**
 * 自定义类注解
 */
@interface table_name{
    String value();
}

@Target(ElementType.FIELD)
@Retention(RetentionPolicy.RUNTIME)
/**
 * 自定义属性注解
 */
@interface field_data{
    String column() default "";
    String type() default "";
    int length() default 0;
}

控制台打印结果：

注解列表:@com.wbk.annotation.table_name(value=db_user)
user的类注解：@com.wbk.annotation.table_name(value=db_user)
==========================================================
id:@com.wbk.annotation.field_data(type=varchar, length=10, column=user_id)
age:@com.wbk.annotation.field_data(type=varchar, length=10, column=user_age)
name:@com.wbk.annotation.field_data(type=varchar, length=10, column=user_name)