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MyBatis-Plus 逻辑删除与唯一索引

IT利刃出鞘 人气:3

简介

说明

本文用示例介绍MyBatis-Plus如何解决逻辑删除与唯一索引的问题。

物理删除与逻辑删除

数据是很重要的，数据库里的数据在删除时一般不会用DELETE语句直接物理删除。

通常的做法是使用逻辑删除，也就是：新加一个标记是否删除的字段，在删除时不是真的删除，而是使用UPDATE语句将某个字段设置为删除状态。例如："deleted_flag"，0表示未删除，其他表示已删除。

MyBatis-Plus默认的逻辑删除

MyBatis-Plus里可以将某个字段标记为逻辑删除字段，方法是：在字段上加@TableLogic注解：

@TableLogicprivate 
Long deletedFlag;

这样一来，操作数据时会自动操作：

查询时：自动加"AND deletedFlag = 0"

删除时：UPDATE SET deletedFlag = 1 ... WHERE ... AND deleted_flag = 0

其对应的默认配置为：

mybatis-plus:
  global-config:
    db-config:
      logic-delete-value: 1 # 逻辑已删除值(默认为 1)
      logic-not-delete-value: 0 # 逻辑未删除值(默认为 0)

MyBatis-Plus默认逻辑删除的问题

假设有一张用户表，有user_name和deleted_flag字段，想给user_name加唯一索引（提高查询速度、确保用户名不重复），这时有如下两种方案：

将user_name设置为唯一索引

将user_name和deleted_flag设置为联合唯一索引

这样也是不行的，比如：

问题复现

依赖

pom.xml

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.3.1.RELEASE</version>
<!--        <version>2.0.0.RELEASE</version>-->
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>com.example</groupId>
    <artifactId>MyBatis-Plus_Simple</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>MyBatis-Plus_Simple</name>
    <description>Demo project for Spring Boot</description>
 
    <properties>
        <java.version>1.8</java.version>
    </properties>
 
    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
 
        <dependency>
            <groupId>com.baomidou</groupId>
            <artifactId>mybatis-plus-boot-starter</artifactId>
            <version>3.3.2</version>
        </dependency>
 
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
 
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
        </dependency>
 
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
        </dependency>
 
        <dependency>
            <groupId>com.github.xiaoymin</groupId>
            <artifactId>knife4j-spring-boot-starter</artifactId>
            <version>3.0.3</version>
        </dependency>
 
    </dependencies>
 
    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>
 
</project>

建库建表

DROP DATABASE IF EXISTS mp;
CREATE DATABASE mp DEFAULT CHARACTER SET utf8;
USE mp;
 
DROP TABLE IF EXISTS `t_user`;
SET NAMES utf8mb4;
 
CREATE TABLE `t_user`
(
    `id`              BIGINT(0) NOT NULL AUTO_INCREMENT,
    `user_name`       VARCHAR(64) NOT NULL COMMENT '用户名（不能重复）',
    `nick_name`       VARCHAR(64) NULL COMMENT '昵称（可以重复）',
    `email`           VARCHAR(64) COMMENT '邮箱',
    `create_time`  DATETIME(0) NULL DEFAULT CURRENT_TIMESTAMP COMMENT '创建时间',
    `update_time` DATETIME(0) NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP COMMENT '修改时间',
    `deleted_flag` BIGINT(0) NOT NULL DEFAULT 0 COMMENT '0：未删除 其他：已删除',
    PRIMARY KEY (`id`) USING BTREE,
    UNIQUE KEY `index_user_name_deleted_flag` (`user_name`, `deleted_flag`),
    KEY `index_create_time`(`create_time`)
) ENGINE = InnoDB COMMENT = '用户';
 
INSERT INTO `t_user` VALUES (1, 'knife', '刀刃', 'abc@qq.com', '2021-01-23 09:33:36', '2021-01-23 09:33:36', 0);
INSERT INTO `t_user` VALUES (2, 'sky', '天蓝', '123@qq.com', '2021-01-24 18:12:21', '2021-01-24 18:12:21', 0);

代码

Entity

package com.example.demo.user.entity;
 
import com.baomidou.mybatisplus.annotation.IdType;
import com.baomidou.mybatisplus.annotation.TableId;
import com.baomidou.mybatisplus.annotation.TableLogic;
import com.baomidou.mybatisplus.annotation.TableName;
import com.baomidou.mybatisplus.extension.activerecord.Model;
import lombok.Data;
 
import java.time.LocalDateTime;
 
@Data
@TableName(value = "t_user")
public class User {
    @TableId(value = "id", type = IdType.AUTO)
    private Long id;
 
    /**
     * 用户名（不能重复）
     */
    private String userName;
 
    /**
     * 昵称（可以重复）
     */
    private String nickName;
 
    /**
     * 邮箱
     */
    private String email;
 
    /**
     * 创建时间
     */
    private LocalDateTime createTime;
 
    /**
     * 修改时间
     */
    private LocalDateTime updateTime;
 
    /**
     * 0：未删除 其他：已删除
     */
    @TableLogic
    private Long deletedFlag;
}

Service

接口

package com.example.demo.user.service;
 
import com.baomidou.mybatisplus.extension.service.IService;
import com.example.demo.user.entity.User;
 
public interface UserService extends IService<User> {
}

实现类

package com.example.demo.user.service.impl;
 
import com.baomidou.mybatisplus.extension.service.impl.ServiceImpl;
import com.example.demo.user.entity.User;
import com.example.demo.user.mapper.UserMapper;
import com.example.demo.user.service.UserService;
import org.springframework.stereotype.Service;
 
@Service
public class UserServiceImpl extends ServiceImpl<UserMapper, User> implements UserService {
}

Controller

package com.example.demo.user.controller;
 
import com.example.demo.user.entity.User;
import com.example.demo.user.service.UserService;
import io.swagger.annotations.Api;
import io.swagger.annotations.ApiOperation;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
 
@Api(tags = "测试")
@RestController
@RequestMapping("test")
public class TestController {
 
    @Autowired
    private UserService userService;
 
    @ApiOperation("删除")
    @PostMapping("delete")
    public String delete(Long id) {
        userService.removeById(id);
        return "remove success";
    }
 
    @ApiOperation("添加")
    @PostMapping("add")
    public User add() {
        User user = new User();
        user.setUserName("sky");
        userService.save(user);
        return user;
    }
}

测试

打开测试页面：http://localhost:8080/doc.html

1. 查看原始数据

2. 删除user_name为“sky”的数据

数据库结果（成功删除）

后端结果

==>  Preparing: UPDATE t_user SET deleted_flag=1 WHERE id=? AND deleted_flag=0 
==> Parameters: 2(Long)
<==    Updates: 1

3. 添加user_name为“sky”的数据

数据库结果（添加成功）

后端结果（添加成功）

==>  Preparing: INSERT INTO t_user ( user_name ) VALUES ( ? ) 
==> Parameters: sky(String)
<==    Updates: 1

4. 删除user_name为“sky”的数据

数据库结果（删除失败）

后端结果（删除失败）

2022-03-20 16:46:09.895 ERROR 15904 --- [nio-8080-exec-7] o.a.c.c.C.[.[.[/].[dispatcherServlet]    : Servlet.service() for servlet [dispatcherServlet] in context with path [] threw exception [Request processing failed; nested exception is org.springframework.dao.DuplicateKeyException: 
### Error updating database.  Cause: java.sql.SQLIntegrityConstraintViolationException: Duplicate entry 'sky-1' for key 't_user.index_user_name_deleted_flag'
### The error may exist in com/example/demo/user/mapper/UserMapper.java (best guess)
### The error may involve com.example.demo.user.mapper.UserMapper.deleteById-Inline
### The error occurred while setting parameters
### SQL: UPDATE t_user SET deleted_flag=1 WHERE id=?  AND deleted_flag=0
### Cause: java.sql.SQLIntegrityConstraintViolationException: Duplicate entry 'sky-1' for key 't_user.index_user_name_deleted_flag'
; Duplicate entry 'sky-1' for key 't_user.index_user_name_deleted_flag'; nested exception is java.sql.SQLIntegrityConstraintViolationException: Duplicate entry 'sky-1' for key 't_user.index_user_name_deleted_flag'] with root cause
 
java.sql.SQLIntegrityConstraintViolationException: Duplicate entry 'sky-1' for key 't_user.index_user_name_deleted_flag'
    at com.mysql.cj.jdbc.exceptions.SQLError.createSQLException(SQLError.java:117) ~[mysql-connector-java-8.0.20.jar:8.0.20]
    at com.mysql.cj.jdbc.exceptions.SQLError.createSQLException(SQLError.java:97) ~[mysql-connector-java-8.0.20.jar:8.0.20]
    at com.mysql.cj.jdbc.exceptions.SQLExceptionsMapping.translateException(SQLExceptionsMapping.java:122) ~[mysql-connector-java-8.0.20.jar:8.0.20]
    at com.mysql.cj.jdbc.ClientPreparedStatement.executeInternal(ClientPreparedStatement.java:953) ~[mysql-connector-java-8.0.20.jar:8.0.20]
    at com.mysql.cj.jdbc.ClientPreparedStatement.execute(ClientPreparedStatement.java:370) ~[mysql-connector-java-8.0.20.jar:8.0.20]
    at com.zaxxer.hikari.pool.ProxyPreparedStatement.execute(ProxyPreparedStatement.java:44) ~[HikariCP-3.4.5.jar:na]
    at com.zaxxer.hikari.pool.HikariProxyPreparedStatement.execute(HikariProxyPreparedStatement.java) ~[HikariCP-3.4.5.jar:na]
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_201]
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:1.8.0_201]
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_201]
    at java.lang.reflect.Method.invoke(Method.java:498) ~[na:1.8.0_201]
    at org.apache.ibatis.logging.jdbc.PreparedStatementLogger.invoke(PreparedStatementLogger.java:59) ~[mybatis-3.5.4.jar:3.5.4]
    at com.sun.proxy.$Proxy110.execute(Unknown Source) ~[na:na]
    at org.apache.ibatis.executor.statement.PreparedStatementHandler.update(PreparedStatementHandler.java:47) ~[mybatis-3.5.4.jar:3.5.4]
    at org.apache.ibatis.executor.statement.RoutingStatementHandler.update(RoutingStatementHandler.java:74) ~[mybatis-3.5.4.jar:3.5.4]
    at com.baomidou.mybatisplus.core.executor.MybatisSimpleExecutor.doUpdate(MybatisSimpleExecutor.java:54) ~[mybatis-plus-core-3.3.2.jar:3.3.2]
    at org.apache.ibatis.executor.BaseExecutor.update(BaseExecutor.java:117) ~[mybatis-3.5.4.jar:3.5.4]
    at com.baomidou.mybatisplus.core.executor.MybatisCachingExecutor.update(MybatisCachingExecutor.java:83) ~[mybatis-plus-core-3.3.2.jar:3.3.2]
    at org.apache.ibatis.session.defaults.DefaultSqlSession.update(DefaultSqlSession.java:197) ~[mybatis-3.5.4.jar:3.5.4]
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_201]
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:1.8.0_201]
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_201]
    at java.lang.reflect.Method.invoke(Method.java:498) ~[na:1.8.0_201]
    at org.mybatis.spring.SqlSessionTemplate$SqlSessionInterceptor.invoke(SqlSessionTemplate.java:426) ~[mybatis-spring-2.0.4.jar:2.0.4]
    at com.sun.proxy.$Proxy72.update(Unknown Source) ~[na:na]
    at org.mybatis.spring.SqlSessionTemplate.update(SqlSessionTemplate.java:287) ~[mybatis-spring-2.0.4.jar:2.0.4]
    at com.baomidou.mybatisplus.core.override.MybatisMapperMethod.execute(MybatisMapperMethod.java:65) ~[mybatis-plus-core-3.3.2.jar:3.3.2]
    at com.baomidou.mybatisplus.core.override.MybatisMapperProxy.invoke(MybatisMapperProxy.java:96) ~[mybatis-plus-core-3.3.2.jar:3.3.2]
    at com.sun.proxy.$Proxy77.deleteById(Unknown Source) ~[na:na]
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_201]
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:1.8.0_201]
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_201]
    at java.lang.reflect.Method.invoke(Method.java:498) ~[na:1.8.0_201]
    at org.springframework.aop.support.AopUtils.invokeJoinpointUsingReflection(AopUtils.java:344) ~[spring-aop-5.2.7.RELEASE.jar:5.2.7.RELEASE]
    at org.springframework.aop.framework.ReflectiveMethodInvocation.invokeJoinpoint(ReflectiveMethodInvocation.java:198) ~[spring-aop-5.2.7.RELEASE.jar:5.2.7.RELEASE]
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:163) ~[spring-aop-5.2.7.RELEASE.jar:5.2.7.RELEASE]
    at org.springframework.dao.support.PersistenceExceptionTranslationInterceptor.invoke(PersistenceExceptionTranslationInterceptor.java:139) ~[spring-tx-5.2.7.RELEASE.jar:5.2.7.RELEASE]
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186) ~[spring-aop-5.2.7.RELEASE.jar:5.2.7.RELEASE]
    at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:212) ~[spring-aop-5.2.7.RELEASE.jar:5.2.7.RELEASE]
    at com.sun.proxy.$Proxy78.deleteById(Unknown Source) ~[na:na]
    at com.baomidou.mybatisplus.extension.service.IService.removeById(IService.java:104) ~[mybatis-plus-extension-3.3.2.jar:3.3.2]
    at com.baomidou.mybatisplus.extension.service.IService$$FastClassBySpringCGLIB$$f8525d18.invoke(<generated>) ~[mybatis-plus-extension-3.3.2.jar:3.3.2]
    at org.springframework.cglib.proxy.MethodProxy.invoke(MethodProxy.java:218) ~[spring-core-5.2.7.RELEASE.jar:5.2.7.RELEASE]
    at org.springframework.aop.framework.CglibAopProxy$DynamicAdvisedInterceptor.intercept(CglibAopProxy.java:687) ~[spring-aop-5.2.7.RELEASE.jar:5.2.7.RELEASE]
    at com.example.demo.user.service.impl.UserServiceImpl$$EnhancerBySpringCGLIB$$328c22ac.removeById(<generated>) ~[classes/:na]
    at com.example.demo.user.controller.TestController.delete(TestController.java:26) ~[classes/:na]
    ...
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) [na:1.8.0_201]
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) [tomcat-embed-core-9.0.36.jar:9.0.36]
    at java.lang.Thread.run(Thread.java:748) [na:1.8.0_201]

解决方案

@TableLogic注解的源码如下：

//
// Source code recreated from a .class file by IntelliJ IDEA
// (powered by FernFlower decompiler)
//
 
package com.baomidou.mybatisplus.annotation;
 
import java.lang.annotation.Documented;
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
 
@Documented
@Retention(RetentionPolicy.RUNTIME)
@Target({ElementType.FIELD, ElementType.ANNOTATION_TYPE})
public @interface TableLogic {
    String value() default "";
 
    String delval() default "";
}

所以方法就是：将delval设置为一个不会冲突的值就可以了，比如：

将delval设置为：“id”

将delval设置为：“NOW()”

说明

delval所指定的字符串，将会直接作为UPDATE语句的SET值，例如，我将delval指定为“abc”，那么删除时的语句就是：UPDATE SET deleted_flag = abc WHERE ...

方案1：将字段设置为id（推荐）

方案简介

在删除时会将逻辑删除字段设置为id的值。

建库建表

DROP DATABASE IF EXISTS mp;
CREATE DATABASE mp DEFAULT CHARACTER SET utf8;
USE mp;
 
DROP TABLE IF EXISTS `t_user`;
SET NAMES utf8mb4;
 
CREATE TABLE `t_user`
(
    `id`              BIGINT(0) NOT NULL AUTO_INCREMENT,
    `user_name`       VARCHAR(64) NOT NULL COMMENT '用户名（不能重复）',
    `nick_name`       VARCHAR(64) NULL COMMENT '昵称（可以重复）',
    `email`           VARCHAR(64) COMMENT '邮箱',
    `create_time`  DATETIME(0) NULL DEFAULT CURRENT_TIMESTAMP COMMENT '创建时间',
    `update_time` DATETIME(0) NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP COMMENT '修改时间',
    `deleted_flag` BIGINT(0) NOT NULL DEFAULT 0 COMMENT '0：未删除 其他：已删除',
    PRIMARY KEY (`id`) USING BTREE,
    UNIQUE KEY `index_user_name_deleted_flag` (`user_name`, `deleted_flag`),
    KEY `index_create_time`(`create_time`)
) ENGINE = InnoDB COMMENT = '用户';
 
INSERT INTO `t_user` VALUES (1, 'knife', '刀刃', 'abc@qq.com', '2021-01-23 09:33:36', '2021-01-23 09:33:36', 0);
INSERT INTO `t_user` VALUES (2, 'sky', '天蓝', '123@qq.com', '2021-01-24 18:12:21', '2021-01-24 18:12:21', 0);

修改Entity

package com.example.demo.user.entity;
 
import com.baomidou.mybatisplus.annotation.IdType;
import com.baomidou.mybatisplus.annotation.TableId;
import com.baomidou.mybatisplus.annotation.TableLogic;
import com.baomidou.mybatisplus.annotation.TableName;
import com.baomidou.mybatisplus.extension.activerecord.Model;
import lombok.Data;
 
import java.time.LocalDateTime;
 
@Data
@TableName(value = "t_user")
public class User {
    @TableId(value = "id", type = IdType.AUTO)
    private Long id;
 
    /**
     * 用户名（不能重复）
     */
    private String userName;
 
    /**
     * 昵称（可以重复）
     */
    private String nickName;
 
    /**
     * 邮箱
     */
    private String email;
 
    /**
     * 创建时间
     */
    private LocalDateTime createTime;
 
    /**
     * 修改时间
     */
    private LocalDateTime updateTime;
 
    /**
     * 0：未删除 其他：已删除
     */
    @TableLogic(delval = "id")
    private Long deletedFlag;
}

测试

打开测试页面：http://localhost:8080/doc.html

1. 查看原始数据

2. 删除user_name为“sky”的数据

数据库结果（成功删除）

后端结果（成功删除）

==>  Preparing: UPDATE t_user SET deleted_flag=id WHERE id=? AND deleted_flag=0 
==> Parameters: 2(Long)
<==    Updates: 1

3. 添加user_name为“sky”的数据

数据库结果（添加成功）

 后端结果（添加成功）

==>  Preparing: INSERT INTO t_user ( user_name ) VALUES ( ? ) 
==> Parameters: sky(String)
<==    Updates: 1

4. 删除user_name为“sky”的数据

数据库结果（删除成功）

后端结果（删除成功）

==>  Preparing: UPDATE t_user SET deleted_flag=id WHERE id=? AND deleted_flag=0 
==> Parameters: 3(Long)
<==    Updates: 1

方案2：将字段设置为当前时间（不推荐）

方案简介

在删除时会将逻辑删除字段设置为NOW()函数的值。

建库建表

DROP DATABASE IF EXISTS mp;
CREATE DATABASE mp DEFAULT CHARACTER SET utf8;
USE mp;
 
DROP TABLE IF EXISTS `t_user`;
SET NAMES utf8mb4;
 
CREATE TABLE `t_user`
(
    `id`              BIGINT(0) NOT NULL AUTO_INCREMENT,
    `user_name`       VARCHAR(64) NOT NULL COMMENT '用户名（不能重复）',
    `nick_name`       VARCHAR(64) NULL COMMENT '昵称（可以重复）',
    `email`           VARCHAR(64) COMMENT '邮箱',
    `create_time`  DATETIME(0) NULL DEFAULT CURRENT_TIMESTAMP COMMENT '创建时间',
    `update_time` DATETIME(0) NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP COMMENT '修改时间',
    `deleted_flag` DATETIME(0) NULL DEFAULT NULL COMMENT 'null：未删除 其他：已删除',
    PRIMARY KEY (`id`) USING BTREE,
    UNIQUE KEY `index_user_name_deleted_flag` (`user_name`, `deleted_flag`),
    KEY `index_create_time`(`create_time`)
) ENGINE = InnoDB COMMENT = '用户';
 
INSERT INTO `t_user` VALUES (1, 'knife', '刀刃', 'abc@qq.com', '2021-01-23 09:33:36', '2021-01-23 09:33:36', null);
INSERT INTO `t_user` VALUES (2, 'sky', '天蓝', '123@qq.com', '2021-01-24 18:12:21', '2021-01-24 18:12:21', null);

修改Entity

package com.example.demo.user.entity;
 
import com.baomidou.mybatisplus.annotation.IdType;
import com.baomidou.mybatisplus.annotation.TableId;
import com.baomidou.mybatisplus.annotation.TableLogic;
import com.baomidou.mybatisplus.annotation.TableName;
import com.baomidou.mybatisplus.extension.activerecord.Model;
import lombok.Data;
 
import java.time.LocalDateTime;
 
@Data
@TableName(value = "t_user")
public class User {
    @TableId(value = "id", type = IdType.AUTO)
    private Long id;
 
    /**
     * 用户名（不能重复）
     */
    private String userName;
 
    /**
     * 昵称（可以重复）
     */
    private String nickName;
 
    /**
     * 邮箱
     */
    private String email;
 
    /**
     * 创建时间
     */
    private LocalDateTime createTime;
 
    /**
     * 修改时间
     */
    private LocalDateTime updateTime;
 
    /**
     * NULL：未删除 其他：已删除
     */
    @TableLogic(value = "NULL", delval = "NOW()")
    private LocalDateTime deletedFlag;
}

测试

 打开测试页面：http://localhost:8080/doc.html

1. 查看原始数据

2. 删除user_name为“sky”的数据

数据库结果（成功删除）

后端结果（成功删除）

==>  Preparing: UPDATE t_user SET deleted_flag=NOW() WHERE id=? AND deleted_flag IS NULL 
==> Parameters: 2(Long)
<==    Updates: 1

3. 添加user_name为“sky”的数据

数据库结果（添加成功）

后端结果（添加成功）

==>  Preparing: INSERT INTO t_user ( user_name ) VALUES ( ? ) 
==> Parameters: sky(String)
<==    Updates: 1

4. 删除user_name为“sky”的数据

数据库结果（删除成功）

后端结果（删除成功）

==>  Preparing: UPDATE t_user SET deleted_flag=NOW() WHERE id=? AND deleted_flag IS NULL 
==> Parameters: 3(Long)
<==    Updates: 1

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