我们在日常开发中，一般会在表里面增加创建人(create_by)、创建时间(create_time)、修改人(update_by)、修改时间(update_time)四个字段。
创建人：新增时，通过上下文获取用户信息。
创建时间：新增时，获取系统当前时间。
修改人：修改时，通过上下文获取用户信息。
修改时间：修改时，获取系统当前时间。
对于这种公共的字段，如果每次都在Sql中进行处理，那是相当繁琐也是没必要的。如果你用的是MyBatis-Plus那么一切就变的简单了。

继承mybatis的Interceptor拦截器

/**
 * Description: mybatis拦截器，自动注入创建人、创建时间、修改人、修改时间
 *
 * @author : laughing
 * DateTime: 2021-05-06 17:13
 */
@Intercepts({@Signature(type = Executor.class, method = "update", args = {MappedStatement.class, Object.class})})
@Slf4j
@SuppressWarnings("all")
public class MybatisSqlInterceptor implements Interceptor {

    @Override
    public Object intercept(Invocation invocation) throws Throwable {
        MappedStatement mappedStatement = (MappedStatement) invocation.getArgs()[0];
        String sqlId = mappedStatement.getId();
        SqlCommandType sqlCommandType = mappedStatement.getSqlCommandType();
        Object parameter = invocation.getArgs()[1];
        if (parameter == null) {
            return invocation.proceed();
        }
        if(SysOperateLog.class.isAssignableFrom(parameter.getClass()) || SysLoginInfo.class.isAssignableFrom(parameter.getClass())){
            return invocation.proceed();
        }
        if (SqlCommandType.INSERT == sqlCommandType) {
            Field[] fields = ConvertUtils.getAllFields(parameter);
            Long userId = SecurityUtils.getUserId();
            for (Field field : fields) {
                try {
                    if ("createBy".equals(field.getName())) {
                        field.setAccessible(true);
                        Object local_createBy = field.get(parameter);
                        field.setAccessible(false);
                        if (local_createBy == null || local_createBy.equals("")) {
                            // 登录人账号
                            field.setAccessible(true);
                            field.set(parameter, userId);
                            field.setAccessible(false);

                        }
                    }
                    // 注入创建时间
                    if ("createTime".equals(field.getName())) {
                        field.setAccessible(true);
                        Object local_createDate = field.get(parameter);
                        field.setAccessible(false);
                        if (local_createDate == null || local_createDate.equals("")) {
                            field.setAccessible(true);
                            field.set(parameter, new Date());
                            field.setAccessible(false);
                        }
                    }
                } catch (Exception e) {
                }
            }
        }
        if (SqlCommandType.UPDATE == sqlCommandType) {
            Long userId = SecurityUtils.getUserId();
            Field[] fields = null;
            if (parameter instanceof MapperMethod.ParamMap) {
                MapperMethod.ParamMap<?> p = (MapperMethod.ParamMap<?>) parameter;
                if (p.containsKey("et")) {
                    parameter = p.get("et");
                } else {
                    parameter = p.get("param1");
                }
                if (parameter == null) {
                    return invocation.proceed();
                }
                fields = ConvertUtils.getAllFields(parameter);
            } else {
                fields = ConvertUtils.getAllFields(parameter);
            }

            for (Field field : fields) {
                try {
                    if ("updateBy".equals(field.getName())) {
                        //获取登录用户信息
                        // 登录账号
                        field.setAccessible(true);
                        field.set(parameter, userId);
                        field.setAccessible(false);

                    }
                    if ("updateTime".equals(field.getName())) {
                        field.setAccessible(true);
                        field.set(parameter, new Date());
                        field.setAccessible(false);
                    }
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        }
        return invocation.proceed();
    }

    @Override
    public Object plugin(Object target) {
        return Plugin.wrap(target, this);
    }

    @Override
    public void setProperties(Properties properties) {
        // TODO Auto-generated method stub
    }

}

通过SqlSessionFactory加载插件

/**
 * Mybatis-Plus配置
 *
 * @author leeframe
 */
@Configuration
@EnableTransactionManagement
public class MyBatisPlusConfig {

    @javax.annotation.Resource
    private Environment env;

    static final String DEFAULT_RESOURCE_PATTERN = "**/*.class";

    private final Logger logger = LoggerFactory.getLogger(MyBatisPlusConfig.class);

    @Bean
    public MybatisPlusInterceptor mybatisPlusInterceptor() {
        MybatisPlusInterceptor interceptor = new MybatisPlusInterceptor();
        // 如果用了分页插件注意先 add TenantLineInnerInterceptor 再 add PaginationInnerInterceptor
        // 用了分页插件必须设置 MybatisConfiguration#useDeprecatedExecutor = false
        // interceptor.addInnerInterceptor(new PaginationInnerInterceptor());

        interceptor.addInnerInterceptor(new TenantLineInnerInterceptor(
                new TenantLineHandler() {
                    // manager_id = 1088248166370832385

                    // 获取租户 ID 值表达式，只支持单个 ID 值
                    @Override
                    public Expression getTenantId() {
                        return new StringValue(SecurityUtils.getOrgCode());
                    }

                    // 这是 default 方法,默认返回 false 表示所有表都需要拼多租户条件,
                    // 这里设置 role表不需要该条件
                    @Override
                    public boolean ignoreTable(String tableName) {
                        return StringUtils.isEmpty(SecurityUtils.getOrgCode()) || LeeFrameConfig.getFilterTableList().stream().anyMatch(e -> e.equalsIgnoreCase(tableName));
                    }

                    @Override
                    public String getTenantIdColumn() {
                        return "org_code";
                    }

                }));
        interceptor.addInnerInterceptor(new PaginationInnerInterceptor(DbType.MYSQL));
        return interceptor;
    }

    @Bean
    public ConfigurationCustomizer configurationCustomizer() {
        return configuration -> configuration.setUseDeprecatedExecutor(false);
    }

    public static String setTypeAliasesPackage(String typeAliasesPackage) {
        ResourcePatternResolver resolver = (ResourcePatternResolver) new PathMatchingResourcePatternResolver();
        MetadataReaderFactory metadataReaderFactory = new CachingMetadataReaderFactory(resolver);
        List<String> allResult = new ArrayList<String>();
        try {
            for (String aliasesPackage : typeAliasesPackage.split(",")) {
                List<String> result = new ArrayList<String>();
                aliasesPackage = ResourcePatternResolver.CLASSPATH_ALL_URL_PREFIX
                        + ClassUtils.convertClassNameToResourcePath(aliasesPackage.trim()) + "/" + DEFAULT_RESOURCE_PATTERN;
                Resource[] resources = resolver.getResources(aliasesPackage);
                if (resources != null && resources.length > 0) {
                    MetadataReader metadataReader = null;
                    for (Resource resource : resources) {
                        if (resource.isReadable()) {
                            metadataReader = metadataReaderFactory.getMetadataReader(resource);
                            try {
                                result.add(Class.forName(metadataReader.getClassMetadata().getClassName()).getPackage().getName());
                            } catch (ClassNotFoundException e) {
                                e.printStackTrace();
                            }
                        }
                    }
                }
                if (result.size() > 0) {
                    HashSet<String> hashResult = new HashSet<String>(result);
                    allResult.addAll(hashResult);
                }
            }
            if (allResult.size() > 0) {
                typeAliasesPackage = String.join(",", (String[]) allResult.toArray(new String[0]));
            } else {
                throw new RuntimeException("mybatis typeAliasesPackage 路径扫描错误,参数typeAliasesPackage:" + typeAliasesPackage + "未找到任何包");
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
        return typeAliasesPackage;
    }

    public Resource[] resolveMapperLocations(String[] mapperLocations) {
        ResourcePatternResolver resourceResolver = new PathMatchingResourcePatternResolver();
        List<Resource> resources = new ArrayList<Resource>();
        if (mapperLocations != null) {
            for (String mapperLocation : mapperLocations) {
                try {
                    Resource[] mappers = resourceResolver.getResources(mapperLocation);
                    resources.addAll(Arrays.asList(mappers));
                } catch (IOException e) {
                    // ignore
                }
            }
        }
        return resources.toArray(new Resource[resources.size()]);
    }

    @Bean
    public SqlSessionFactory sqlSessionFactory(DataSource dataSource) throws Exception {
        String typeAliasesPackage = env.getProperty("mybatisPlus.typeAliasesPackage");
        String mapperLocations = env.getProperty("mybatisPlus.mapperLocations");
        String configLocation = env.getProperty("mybatisPlus.configLocation");
        typeAliasesPackage = setTypeAliasesPackage(typeAliasesPackage);
        VFS.addImplClass(SpringBootVFS.class);
        final MybatisSqlSessionFactoryBean sessionFactory = new MybatisSqlSessionFactoryBean();
        sessionFactory.setDataSource(dataSource);
        sessionFactory.setTypeAliasesPackage(typeAliasesPackage);
        sessionFactory.setMapperLocations(resolveMapperLocations(StringUtils.split(mapperLocations, ",")));
        sessionFactory.setConfigLocation(new DefaultResourceLoader().getResource(configLocation));
        sessionFactory.setPlugins(mybatisSqlInterceptor());
        return sessionFactory.getObject();
    }


    @Bean
    public MybatisSqlInterceptor mybatisSqlInterceptor() {
        MybatisSqlInterceptor mybatisSqlInterceptor = new MybatisSqlInterceptor();
        Properties properties = new Properties();
        mybatisSqlInterceptor.setProperties(properties);
        return mybatisSqlInterceptor;
    }

}