JDA机器人封禁/踢出用户时即便用户私信开放也无法发送DM问题排查

• 核心为异步任务执行顺序异常：JDA的queue()方法属于异步非阻塞调用，提交私信发送任务后，程序不会等待该任务执行完成，就会立即触发后续的踢人逻辑。绝大多数场景下踢人操作会先执行完毕，此时被操作用户已与机器人无共同服务器，Discord官方策略会直接拒绝机器人的私信发送请求，即便用户此前开放了私信权限也无法成功发送。
• 代码存在非功能性拼写错误：私信内容中he reason缺少首字母T，应为The reason，不影响发送成功率但会导致内容展示异常。

调整异步任务的串联逻辑，将踢人/封禁操作绑定到私信发送任务的执行链路后，确保无论私信发送成功或失败，都会在私信请求处理完成后再执行用户移除操作，避免用户提前被移出服务器导致私信被Discord官方策略拦截。封禁场景的修复逻辑完全一致，仅需将kick方法替换为对应的封禁方法即可。

修复后的代码如下：

public static void kickUser(@NotNull Member member, @NotNull Member author,
                            @NotNull String reason, long userId, @NotNull SlashCommandEvent event) {
    String guildName = event.getGuild().getName();
    // 构造发送私信的RestAction
    RestAction<Message> sendDmAction = event.getJDA()
            .openPrivateChannelById(userId)
            .flatMap(channel -> channel.sendMessage(
                    """
                            Hey there, sorry to tell you but unfortunately you have been kicked from the guild %s.
                            If you think this was a mistake, please contact a moderator or admin of the guild.
                            The reason for the kick is: %s
                            """.formatted(guildName, reason)));

    // 先执行私信发送，无论成功失败都执行踢人逻辑
    sendDmAction
            .onErrorFlatMap(throwable -> {
                logger.info("I could not dm the user '{}' to inform them that they were kicked. {}", userId, throwable);
                // 异常时返回空RestAction，保证后续流程正常执行
                return RestAction.empty();
            })
            // 私信流程处理完成后再执行踢人操作
            .flatMap(ignored -> event.getGuild().kick(member, reason))
            .flatMap(ignored -> event.reply(member.getUser().getAsTag() + " was kicked by "
                    + author.getUser().getAsTag() + " for: " + reason))
            .queue();

    logger.info(" '{} ({})' kicked the user '{} ({})' due to reason being '{}'",
            author.getUser().getAsTag(), author.getIdLong(), member.getUser().getAsTag(),
            userId, reason);
}

内容的提问来源于stack exchange，提问作者Yusuf.I