Error when building LineMessagingClient ( Local server running on Docker)

Question

### 前提・実現したいこと
I want to build LineMessagingClient with channel_token which is saved inside my local DB.

### 発生している問題・エラーメッセージ
When I test API with Postman, it only returned 502 Bad gateway and [log.debug("Build LineMessagingClient");] couldn't be reached when I check app log.

### 該当のソースコード
```
private LineMessagingClient getLineMessagingClient() {
        LineMessagingClient client = LineMessagingClient.builder(channel_token)
                .build();
        log.debug("Build LineMessagingClient");
        return client;
    }
```
channel_token get from local DB.

### 試したこと
I try to create another method with connect to LINE by HttpURLConnection and it worked.
But I want to use SDK instead.

### 補足情報（FW/ツールのバージョンなど）
Java: JDK1.8.0_321.jdk
LINE Messaging API SDK : v.4.8.0
Refer:
https://github.com/line/line-bot-sdk-java/tree/master/line-bot-api-client
Synopsis
I'm running my server on Docker.

Please help me.
Thanks!

TheoFin · Accepted Answer

I figured that beside LINE Messaging API SDK, I need to add okhttp3, retrofit, okio, etc ( about 17 additional libraries).
After included all of additional libraries, it works.

TheoFin · Answer

@ksyt:
Thank for reply me.

1. what happens if you write channel-access-token directly in the code?
It is same result. There is still 502 error.

2. did you read error message?
I cannot see any error message except 502 error of nginx.
Is there any way to catch error when run build()?
`LineMessagingClient.builder(channel_token).build();`
Is that enough if I config only channel_token for connect to LINE server?

ksyt · Answer

1. what happens if you write channel-access-token directly in the code?
2. did you read error message?

Q&A

Error when building LineMessagingClient ( Local server running on Docker)

前提・実現したいこと

発生している問題・エラーメッセージ

該当のソースコード

試したこと

補足情報（FW/ツールのバージョンなど）