public static synchronized void join(Mapper mapper) {
        if (Objects.isNull(mapper)) {
            return;
        }
        putMapper(mapper);
        LOGGER.info("[MapperManager] join successfully.");
    }
@Test
    void testJoin() {
        MapperManager.join(new AbstractMapperByMysql() {
            @Override
            public String getTableName() {
                return "test";
            }

            @Override
            public String getDataSource() {
                return DataSourceConstant.MYSQL;
            }
        });
        MapperManager instance = MapperManager.instance(false);
        Mapper mapper = instance.findMapper(DataSourceConstant.MYSQL, "test");
        assertNotNull(mapper);
    }