MyBatis-Plus解決邏輯刪除與唯一索引的問題

更新時(shí)間：2022年08月09日 15:47:31 作者：IT利刃出鞘

本文主要介紹了MyBatis-Plus解決邏輯刪除與唯一索引的問題，文中通過示例代碼介紹的非常詳細(xì)，對大家的學(xué)習(xí)或者工作具有一定的參考學(xué)習(xí)價(jià)值，需要的朋友們下面隨著小編來一起學(xué)習(xí)學(xué)習(xí)吧

簡介

說明

本文用示例介紹MyBatis-Plus如何解決邏輯刪除與唯一索引的問題。

物理刪除與邏輯刪除

數(shù)據(jù)是很重要的，數(shù)據(jù)庫里的數(shù)據(jù)在刪除時(shí)一般不會用DELETE語句直接物理刪除。

通常的做法是使用邏輯刪除，也就是：新加一個標(biāo)記是否刪除的字段，在刪除時(shí)不是真的刪除，而是使用UPDATE語句將某個字段設(shè)置為刪除狀態(tài)。例如："deleted_flag"，0表示未刪除，其他表示已刪除。

MyBatis-Plus默認(rèn)的邏輯刪除

MyBatis-Plus里可以將某個字段標(biāo)記為邏輯刪除字段，方法是：在字段上加@TableLogic注解：

@TableLogicprivate 
Long deletedFlag;

這樣一來，操作數(shù)據(jù)時(shí)會自動操作：

查詢時(shí)：自動加"AND deletedFlag = 0"

刪除時(shí)：UPDATE SET deletedFlag = 1 ... WHERE ... AND deleted_flag = 0

其對應(yīng)的默認(rèn)配置為：

mybatis-plus:
  global-config:
    db-config:
      logic-delete-value: 1 # 邏輯已刪除值(默認(rèn)為 1)
      logic-not-delete-value: 0 # 邏輯未刪除值(默認(rèn)為 0)

MyBatis-Plus默認(rèn)邏輯刪除的問題

假設(shè)有一張用戶表，有user_name和deleted_flag字段，想給user_name加唯一索引（提高查詢速度、確保用戶名不重復(fù)），這時(shí)有如下兩種方案：

將user_name設(shè)置為唯一索引

這樣是不行的，比如：有個用戶名為“Tony”，刪除了，又有一個用戶注冊，注冊為“Tony”，這就會報(bào)錯。報(bào)錯的信息是這樣的：Duplicate entry 'Tony' for key 't_user.index_user_name'

將user_name和deleted_flag設(shè)置為聯(lián)合唯一索引

這樣也是不行的，比如：

有個用戶名為“Tony”，刪除了，這樣聯(lián)合索引為“Tony-1”。
又有一個用戶注冊，注冊為“Tony”，這不會報(bào)錯，此時(shí)新用戶聯(lián)合索引為“Tony-0”
新用戶刪除，會報(bào)錯：因?yàn)榇藭r(shí)新用戶聯(lián)合索引為“Tony-1”，數(shù)據(jù)庫已經(jīng)有了。報(bào)錯的信息是這樣的：Duplicate entry 'Tony-1' for key 't_user.index_user_name_deleted_flag'

問題復(fù)現(xiàn)

依賴

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>

建庫建表

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 '用戶名（不能重復(fù)）',
    `nick_name`       VARCHAR(64) NULL COMMENT '昵稱（可以重復(fù)）',
    `email`           VARCHAR(64) COMMENT '郵箱',
    `create_time`  DATETIME(0) NULL DEFAULT CURRENT_TIMESTAMP COMMENT '創(chuàng)建時(shí)間',
    `update_time` DATETIME(0) NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP COMMENT '修改時(shí)間',
    `deleted_flag` BIGINT(0) NOT NULL DEFAULT 0 COMMENT '0：未刪除 其他：已刪除',
    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 = '用戶';
 
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', '天藍(lán)', '123@qq.com', '2021-01-24 18:12:21', '2021-01-24 18:12:21', 0);

代碼

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;
 
    /**
     * 用戶名（不能重復(fù)）
     */
    private String userName;
 
    /**
     * 昵稱（可以重復(fù)）
     */
    private String nickName;
 
    /**
     * 郵箱
     */
    private String email;
 
    /**
     * 創(chuàng)建時(shí)間
     */
    private LocalDateTime createTime;
 
    /**
     * 修改時(shí)間
     */
    private LocalDateTime updateTime;
 
    /**
     * 0：未刪除 其他：已刪除
     */
    @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> {
}

實(shí)現(xiàn)類

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 = "測試")
@RestController
@RequestMapping("test")
public class TestController {
 
    @Autowired
    private UserService userService;
 
    @ApiOperation("刪除")
    @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;
    }
}

測試

打開測試頁面：http://localhost:8080/doc.html

1. 查看原始數(shù)據(jù)

2. 刪除user_name為“sky”的數(shù)據(jù)

數(shù)據(jù)庫結(jié)果（成功刪除）

后端結(jié)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為“sky”的數(shù)據(jù)

數(shù)據(jù)庫結(jié)果（添加成功）

后端結(jié)果（添加成功）

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

4. 刪除user_name為“sky”的數(shù)據(jù)

數(shù)據(jù)庫結(jié)果（刪除失?。?/p>

后端結(jié)果（刪除失?。?/p>

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]

解決方案

@TableLogic注解的源碼如下：

//
// 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 "";
}

value：表示刪除標(biāo)記字段的正常的值（未刪除時(shí)的值）。默認(rèn)為0
delval：表示刪除標(biāo)記字段的刪除時(shí)的值（刪除后的值）。默認(rèn)為1

所以方法就是：將delval設(shè)置為一個不會沖突的值就可以了，比如：

將delval設(shè)置為：“id”

這樣在刪除時(shí)會將deleted_flag設(shè)置為id的值

將delval設(shè)置為：“NOW()”

這樣在刪除時(shí)會將deleted_flag設(shè)置為刪除的時(shí)間

說明

delval所指定的字符串，將會直接作為UPDATE語句的SET值，例如，我將delval指定為“abc”，那么刪除時(shí)的語句就是：UPDATE SET deleted_flag = abc WHERE ...

方案1：將字段設(shè)置為id（推薦）

方案簡介

在刪除時(shí)會將邏輯刪除字段設(shè)置為id的值。

建庫建表

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 '用戶名（不能重復(fù)）',
    `nick_name`       VARCHAR(64) NULL COMMENT '昵稱（可以重復(fù)）',
    `email`           VARCHAR(64) COMMENT '郵箱',
    `create_time`  DATETIME(0) NULL DEFAULT CURRENT_TIMESTAMP COMMENT '創(chuàng)建時(shí)間',
    `update_time` DATETIME(0) NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP COMMENT '修改時(shí)間',
    `deleted_flag` BIGINT(0) NOT NULL DEFAULT 0 COMMENT '0：未刪除 其他：已刪除',
    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 = '用戶';
 
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', '天藍(lán)', '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;
 
    /**
     * 用戶名（不能重復(fù)）
     */
    private String userName;
 
    /**
     * 昵稱（可以重復(fù)）
     */
    private String nickName;
 
    /**
     * 郵箱
     */
    private String email;
 
    /**
     * 創(chuàng)建時(shí)間
     */
    private LocalDateTime createTime;
 
    /**
     * 修改時(shí)間
     */
    private LocalDateTime updateTime;
 
    /**
     * 0：未刪除 其他：已刪除
     */
    @TableLogic(delval = "id")
    private Long deletedFlag;
}

測試

打開測試頁面：http://localhost:8080/doc.html

1. 查看原始數(shù)據(jù)

2. 刪除user_name為“sky”的數(shù)據(jù)

數(shù)據(jù)庫結(jié)果（成功刪除）

后端結(jié)果（成功刪除）

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

3. 添加user_name為“sky”的數(shù)據(jù)

數(shù)據(jù)庫結(jié)果（添加成功）

后端結(jié)果（添加成功）

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

4. 刪除user_name為“sky”的數(shù)據(jù)

數(shù)據(jù)庫結(jié)果（刪除成功）

后端結(jié)果（刪除成功）

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

方案2：將字段設(shè)置為當(dāng)前時(shí)間（不推薦）

方案簡介

在刪除時(shí)會將邏輯刪除字段設(shè)置為NOW()函數(shù)的值。

建庫建表

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 '用戶名（不能重復(fù)）',
    `nick_name`       VARCHAR(64) NULL COMMENT '昵稱（可以重復(fù)）',
    `email`           VARCHAR(64) COMMENT '郵箱',
    `create_time`  DATETIME(0) NULL DEFAULT CURRENT_TIMESTAMP COMMENT '創(chuàng)建時(shí)間',
    `update_time` DATETIME(0) NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP COMMENT '修改時(shí)間',
    `deleted_flag` DATETIME(0) NULL DEFAULT NULL COMMENT 'null：未刪除 其他：已刪除',
    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 = '用戶';
 
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', '天藍(lán)', '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;
 
    /**
     * 用戶名（不能重復(fù)）
     */
    private String userName;
 
    /**
     * 昵稱（可以重復(fù)）
     */
    private String nickName;
 
    /**
     * 郵箱
     */
    private String email;
 
    /**
     * 創(chuàng)建時(shí)間
     */
    private LocalDateTime createTime;
 
    /**
     * 修改時(shí)間
     */
    private LocalDateTime updateTime;
 
    /**
     * NULL：未刪除 其他：已刪除
     */
    @TableLogic(value = "NULL", delval = "NOW()")
    private LocalDateTime deletedFlag;
}

測試

打開測試頁面：http://localhost:8080/doc.html

1. 查看原始數(shù)據(jù)