MyBatis-利用切面实现公有字段自动填充(非MyBatisPlus方式)

需求：

在MyBatis框架中，如何对createBy，createTime，updateBy等这些公有字段实现自动填充呢？

网上搜了很多，实现的方案全是采用集成MyBatisPlus，利用其封装好的方法来实现的。。。。。

数据准备：

1、准备一张数据库表

CREATE TABLE `user` (
  `id` varchar(36) NOT NULL,
  `username` varchar(64) NOT NULL,
  `password` varchar(64) NOT NULL,
  `create_by` varchar(32) DEFAULT NULL,
  `create_time` datetime DEFAULT NULL,
  `update_by` varchar(32) DEFAULT NULL,
  `update_time` datetime DEFAULT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_0900_ai_ci;

2、新建一个SpringBoot工程

3、引入依赖：

        <dependency>
			<groupId>com.baomidou</groupId>
			<artifactId>mybatis-plus-boot-starter</artifactId>
			<version>3.5.2</version>
		</dependency>

		<dependency>
			<groupId>com.mysql</groupId>
			<artifactId>mysql-connector-j</artifactId>
			<version>8.0.33</version>
		</dependency>

		<!--切面-->
		<dependency>
			<groupId>org.aspectj</groupId>
			<artifactId>aspectjweaver</artifactId>
			<version>1.9.7</version>
		</dependency>

4、公有字段实体类准备：

自定义注解

package com.example.domain;

import com.example.annoation.createAt;
import com.example.annoation.createDate;
import com.example.annoation.updateAt;
import com.example.annoation.updateDate;

import java.util.Date;

public class BaseEntity {

    @createAt
    private String createBy;

    @createDate
    private Date createTime;

    @updateAt
    private String updateBy;

    @updateDate
    private Date updateTime;


    public String getCreateBy() {
        return createBy;
    }

    public void setCreateBy(String createBy) {
        this.createBy = createBy;
    }

    public Date getCreateTime() {
        return createTime;
    }

    public void setCreateTime(Date createTime) {
        this.createTime = createTime;
    }

    public String getUpdateBy() {
        return updateBy;
    }

    public void setUpdateBy(String updateBy) {
        this.updateBy = updateBy;
    }

    public Date getUpdateTime() {
        return updateTime;
    }

    public void setUpdateTime(Date updateTime) {
        this.updateTime = updateTime;
    }


}

package com.example.domain;

public class User extends BaseEntity{
    private String id;

    private String username;

    private String password;

    public String getId() {
        return id;
    }

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

    public String getUsername() {
        return username;
    }

    public void setUsername(String username) {
        this.username = username;
    }

    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }
}

切面实现：

1、自定义注解

/**
 * 创建人
 */
@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.FIELD)
public @interface createAt {
}

/**
 * 创建时间
 */
@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.FIELD)
public @interface createDate {
}

/**
 * 更新人
 */
@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.FIELD)
public @interface updateAt {
}

/**
 * 更新时间
 */
@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.FIELD)
public @interface updateDate {
}

2、利用反射以及切面编程来实现

package com.example.aspect;

import com.example.annoation.createAt;
import com.example.annoation.createDate;
import com.example.annoation.updateAt;
import com.example.annoation.updateDate;
import org.aspectj.lang.annotation.Aspect;
import org.aspectj.lang.annotation.Before;
import org.springframework.stereotype.Component;

import java.lang.reflect.Field;
import java.util.Date;

@Aspect
@Component
public class SqlAspect {

    @Before("execution(* com.example..*(..)) && args(entity,..)")
    public void beforeSaveOrUpdate(Object entity) throws IllegalAccessException {
        if (entity != null) {
            // 获取所有字段，包括继承的字段
            Class<?> clazz = entity.getClass();
            while (clazz != null) {
                Field[] fields = clazz.getDeclaredFields();
                for (Field field : fields) {
                    field.setAccessible(true); // 设置可访问私有字段
                    if (field.isAnnotationPresent(createAt.class)) {
                        // 当前登录用户ID
                        field.set(entity, "login_user_id");
                    } else if (field.isAnnotationPresent(createDate.class)) {
                        // 当前时间
                        field.set(entity, new Date());
                    } else if (field.isAnnotationPresent(updateAt.class)) {
                        // 当前登录用户ID
                        field.set(entity, "login_user_id");
                    } else if (field.isAnnotationPresent(updateDate.class)) {
                        // 当前时间
                        field.set(entity, new Date());
                    }
                }
                clazz = clazz.getSuperclass();
            }
        }
    }

}

最终效果：