注意事项

一：如果插入时有设置的值就使用之前设置的值，不带时才自动赋值。

二：xml文件中必须带有需要自动赋值的字段，否则无法知道赋值（如id、create_time、update_time）
在这里插入图片描述

代码详解

注解：

@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.FIELD)
public @interface AutoId {
    IdType type() default IdType.SNOWFLAKE;
    enum IdType{
        UUID,
        SNOWFLAKE,
    }
}

@Retention(RetentionPolicy.RUNTIME)
@Target({ElementType.FIELD})
public @interface CreateTime {
    String value() default "";
}

@Retention(RetentionPolicy.RUNTIME)
@Target({ElementType.FIELD})
public @interface UpdateTime {
    String value() default "";
}

拦截器配置：

@Slf4j
@Component
@Intercepts({@Signature(type = Executor.class, method = "update", args = {MappedStatement.class, Object.class})})
public class MybatisAutoFillingInterceptor implements Interceptor {

    @Override
    public Object intercept(Invocation invocation) throws Throwable {
        MappedStatement mappedStatement = (MappedStatement) invocation.getArgs()[0];
        // 获取 SQL 命令
        SqlCommandType sqlCommandType = mappedStatement.getSqlCommandType();
        //只判断新增和修改
        if (SqlCommandType.INSERT.equals(sqlCommandType) || SqlCommandType.UPDATE.equals(sqlCommandType)) {
            // 获取参数
            Object parameter = invocation.getArgs()[1];
            //批量操作时
            if (parameter instanceof MapperMethod.ParamMap) {
                MapperMethod.ParamMap map = (MapperMethod.ParamMap) parameter;
                Object obj = map.get("list");
                List<?> list = (List<?>) obj;
                if (list != null) {
                    for (Object o : list) {
                        setParameter(o, sqlCommandType);
                    }
                }
            } else {
                setParameter(parameter, sqlCommandType);
            }
        }
        return invocation.proceed();
    }

    public void setParameter(Object parameter, SqlCommandType sqlCommandType) throws Throwable {
        Class<?> aClass = parameter.getClass();
        Field[] declaredFields;
        declaredFields = aClass.getDeclaredFields();
        for (Field field : declaredFields) {
            LocalDateTime now = LocalDateTime.now();
            if (SqlCommandType.INSERT.equals(sqlCommandType)) {
                if (field.getAnnotation(CreateTime.class) != null) {
                    field.setAccessible(true);
                    if (field.get(parameter) == null) {
                        field.set(parameter, now);
                    }
                }
                if (field.getAnnotation(UpdateTime.class) != null) {
                    field.setAccessible(true);
                    if (field.get(parameter) == null) {
                        field.set(parameter, now);
                    }
                }
                if (field.getAnnotation(AutoId.class) != null ) {
                    field.setAccessible(true);
                    if (field.get(parameter) == null) {
                        if (Objects.equals(field.getAnnotation(AutoId.class).type(), AutoId.IdType.SNOWFLAKE)) {
                            field.set(parameter, IdUtil.getSnowflakeNextId());
                        } else if (Objects.equals(field.getAnnotation(AutoId.class).type(), AutoId.IdType.UUID)) {
                            field.set(parameter, IdUtil.simpleUUID());
                        }
                    }
                }
            }
            if (SqlCommandType.UPDATE.equals(sqlCommandType)) {
                if (field.getAnnotation(UpdateTime.class) != null) {
                    field.setAccessible(true);
                    if (field.get(parameter) == null) {
                        field.set(parameter, now);
                    }
                }
            }
        }
    }
}

测试：

@Data
public class Temp implements Serializable {

    @AutoId
    private Long id;

    private String name;

    @CreateTime
    private LocalDateTime createTime;

    @UpdateTime
    private LocalDateTime updateTime;
}

@SpringBootTest
class MyBatisPlusApplicationTests {

    @Resource
    private TempMapper tempMapper;

    @Test
    void mapper() {
        Temp temp = new Temp();
        temp.setName("自动ID222");
        temp.setCreateTime(LocalDateTime.now().plusYears(11L));
        tempMapper.insert(temp);
    }
}