[Item62] 타입 안전 제일

Item62에서는 적절한 타입이 있다면 문자열 사용을 피하라 말한다

책에서는 예제로 ThreadLocal을 들었고, 제네릭을 버무려 type-safe한 모습으로 만들어냈다

이 보다 더 와닿을 예제로 웹개발 시에 모든 값을 타입과 상관없이 String 타입으로 받아버리는 것이 있다

자바 스프링을 사용한다면 ConversionService에 의해 대부분의 타입이 변환이 되는데도 불구하고

String으로 받아버리고 필요하다면 개발자가 직접 형변환을 때려주는 코드를 본 적이 있다

상당한 레거시 프로젝트였는데 자바17까지 깔짝이며 최첨단으로 공부하던 신입 개발자 눈에는 당최 이해할 수가 없는 형태였다

 

DefaultConversionService.addScalarConverters

 

ConversionService 문서를 보면 3.0부터 지원이 됐다고 하는데 그럼에도 안 쓴 이유를 추측해보자면 아래와 같을 것이다

1. 스프링을 신뢰하지 못 해서

2. 예전부터 String으로 받던 걸 리팩토링하기 귀찮아서

 

35세 때까지 여전히 가난하다면 누구도 탓할 수 없다. 그건 당신 자신의 탓이다

마윈이 했던 말이라고 한다

소프트웨어에서도 마찬가지로 초반엔 성장을 위해 어쩔 수 없이 개판을 쳐놨더라도

어느 정도 성숙기에 접어들고도 레거시가 그득하다면 개발팀의 잘못이라 할 수밖에 없다

이직한 후 실무 코드를 보고 깜짝 놀랐는데

10년이 넘은 코드인데도 불구하고 계속된 리팩토링이 있었고, 이해할 수 없을 정도의 퀄리티는 보지 못 했다는 점이다

일감이 주어지기 전까지 기존 코드를 사람이 이해하기 쉬운 형태로 바꿔나가는 리팩토링을 조금 진행했는데

애초에 깔끔하게 작성되어 있었으니 건드릴 부분도 많지 않았고 진행하면서도 신기했다

몇몇 코드는 deprecated API를 사용하기도 했고 라이브러리 버전도 최신은 아니지만

개발자가 신경 쓰면서 꾸준히 리팩토링 한다면 이렇게도 만들어질 수 있구나 싶었다

 

이 외에도 레거시에서 이해할 수 없던 것이 하나 더 있는데 멀쩡히 Enum이나 문자로 전달할 수 있는 형태인 것 같은데도

상수로 지정해놓고 0, 1, 2로 전달하는 것이었는데 바이트를 하나라도 아껴서 지구를 보호하고자 하는 마음은 정말 가상하다

그럼에도 굳이 이렇게 해야 할까 라는 생각이 들었다

 

이런 노력을 무산케 하는 대기업의 횡포를 살펴보자, Github의 Issue 관련 API를 참고해보면 아래와 같이 살포시 찔러줄 시

curl \
  -H "Accept: application/vnd.github+json" \ 
  -H "Authorization: token <TOKEN>" \
  https://api.github.com/issues

 

조선시대 상소문과 같은 response가 온다 (스압 주의)

[
  {
    "id": 1,
    "node_id": "MDU6SXNzdWUx",
    "url": "https://api.github.com/repos/octocat/Hello-World/issues/1347",
    "repository_url": "https://api.github.com/repos/octocat/Hello-World",
    "labels_url": "https://api.github.com/repos/octocat/Hello-World/issues/1347/labels{/name}",
    "comments_url": "https://api.github.com/repos/octocat/Hello-World/issues/1347/comments",
    "events_url": "https://api.github.com/repos/octocat/Hello-World/issues/1347/events",
    "html_url": "https://github.com/octocat/Hello-World/issues/1347",
    "number": 1347,
    "state": "open",
    "title": "Found a bug",
    "body": "I'm having a problem with this.",
    "user": {
      "login": "octocat",
      "id": 1,
      "node_id": "MDQ6VXNlcjE=",
      "avatar_url": "https://github.com/images/error/octocat_happy.gif",
      "gravatar_id": "",
      "url": "https://api.github.com/users/octocat",
      "html_url": "https://github.com/octocat",
      "followers_url": "https://api.github.com/users/octocat/followers",
      "following_url": "https://api.github.com/users/octocat/following{/other_user}",
      "gists_url": "https://api.github.com/users/octocat/gists{/gist_id}",
      "starred_url": "https://api.github.com/users/octocat/starred{/owner}{/repo}",
      "subscriptions_url": "https://api.github.com/users/octocat/subscriptions",
      "organizations_url": "https://api.github.com/users/octocat/orgs",
      "repos_url": "https://api.github.com/users/octocat/repos",
      "events_url": "https://api.github.com/users/octocat/events{/privacy}",
      "received_events_url": "https://api.github.com/users/octocat/received_events",
      "type": "User",
      "site_admin": false
    },
    "labels": [
      {
        "id": 208045946,
        "node_id": "MDU6TGFiZWwyMDgwNDU5NDY=",
        "url": "https://api.github.com/repos/octocat/Hello-World/labels/bug",
        "name": "bug",
        "description": "Something isn't working",
        "color": "f29513",
        "default": true
      }
    ],
    "assignee": {
      "login": "octocat",
      "id": 1,
      "node_id": "MDQ6VXNlcjE=",
      "avatar_url": "https://github.com/images/error/octocat_happy.gif",
      "gravatar_id": "",
      "url": "https://api.github.com/users/octocat",
      "html_url": "https://github.com/octocat",
      "followers_url": "https://api.github.com/users/octocat/followers",
      "following_url": "https://api.github.com/users/octocat/following{/other_user}",
      "gists_url": "https://api.github.com/users/octocat/gists{/gist_id}",
      "starred_url": "https://api.github.com/users/octocat/starred{/owner}{/repo}",
      "subscriptions_url": "https://api.github.com/users/octocat/subscriptions",
      "organizations_url": "https://api.github.com/users/octocat/orgs",
      "repos_url": "https://api.github.com/users/octocat/repos",
      "events_url": "https://api.github.com/users/octocat/events{/privacy}",
      "received_events_url": "https://api.github.com/users/octocat/received_events",
      "type": "User",
      "site_admin": false
    },
    "assignees": [
      {
        "login": "octocat",
        "id": 1,
        "node_id": "MDQ6VXNlcjE=",
        "avatar_url": "https://github.com/images/error/octocat_happy.gif",
        "gravatar_id": "",
        "url": "https://api.github.com/users/octocat",
        "html_url": "https://github.com/octocat",
        "followers_url": "https://api.github.com/users/octocat/followers",
        "following_url": "https://api.github.com/users/octocat/following{/other_user}",
        "gists_url": "https://api.github.com/users/octocat/gists{/gist_id}",
        "starred_url": "https://api.github.com/users/octocat/starred{/owner}{/repo}",
        "subscriptions_url": "https://api.github.com/users/octocat/subscriptions",
        "organizations_url": "https://api.github.com/users/octocat/orgs",
        "repos_url": "https://api.github.com/users/octocat/repos",
        "events_url": "https://api.github.com/users/octocat/events{/privacy}",
        "received_events_url": "https://api.github.com/users/octocat/received_events",
        "type": "User",
        "site_admin": false
      }
    ],
    "milestone": {
      "url": "https://api.github.com/repos/octocat/Hello-World/milestones/1",
      "html_url": "https://github.com/octocat/Hello-World/milestones/v1.0",
      "labels_url": "https://api.github.com/repos/octocat/Hello-World/milestones/1/labels",
      "id": 1002604,
      "node_id": "MDk6TWlsZXN0b25lMTAwMjYwNA==",
      "number": 1,
      "state": "open",
      "title": "v1.0",
      "description": "Tracking milestone for version 1.0",
      "creator": {
        "login": "octocat",
        "id": 1,
        "node_id": "MDQ6VXNlcjE=",
        "avatar_url": "https://github.com/images/error/octocat_happy.gif",
        "gravatar_id": "",
        "url": "https://api.github.com/users/octocat",
        "html_url": "https://github.com/octocat",
        "followers_url": "https://api.github.com/users/octocat/followers",
        "following_url": "https://api.github.com/users/octocat/following{/other_user}",
        "gists_url": "https://api.github.com/users/octocat/gists{/gist_id}",
        "starred_url": "https://api.github.com/users/octocat/starred{/owner}{/repo}",
        "subscriptions_url": "https://api.github.com/users/octocat/subscriptions",
        "organizations_url": "https://api.github.com/users/octocat/orgs",
        "repos_url": "https://api.github.com/users/octocat/repos",
        "events_url": "https://api.github.com/users/octocat/events{/privacy}",
        "received_events_url": "https://api.github.com/users/octocat/received_events",
        "type": "User",
        "site_admin": false
      },
      "open_issues": 4,
      "closed_issues": 8,
      "created_at": "2011-04-10T20:09:31Z",
      "updated_at": "2014-03-03T18:58:10Z",
      "closed_at": "2013-02-12T13:22:01Z",
      "due_on": "2012-10-09T23:39:01Z"
    },
    "locked": true,
    "active_lock_reason": "too heated",
    "comments": 0,
    "pull_request": {
      "url": "https://api.github.com/repos/octocat/Hello-World/pulls/1347",
      "html_url": "https://github.com/octocat/Hello-World/pull/1347",
      "diff_url": "https://github.com/octocat/Hello-World/pull/1347.diff",
      "patch_url": "https://github.com/octocat/Hello-World/pull/1347.patch"
    },
    "closed_at": null,
    "created_at": "2011-04-22T13:33:48Z",
    "updated_at": "2011-04-22T13:33:48Z",
    "repository": {
      "id": 1296269,
      "node_id": "MDEwOlJlcG9zaXRvcnkxMjk2MjY5",
      "name": "Hello-World",
      "full_name": "octocat/Hello-World",
      "owner": {
        "login": "octocat",
        "id": 1,
        "node_id": "MDQ6VXNlcjE=",
        "avatar_url": "https://github.com/images/error/octocat_happy.gif",
        "gravatar_id": "",
        "url": "https://api.github.com/users/octocat",
        "html_url": "https://github.com/octocat",
        "followers_url": "https://api.github.com/users/octocat/followers",
        "following_url": "https://api.github.com/users/octocat/following{/other_user}",
        "gists_url": "https://api.github.com/users/octocat/gists{/gist_id}",
        "starred_url": "https://api.github.com/users/octocat/starred{/owner}{/repo}",
        "subscriptions_url": "https://api.github.com/users/octocat/subscriptions",
        "organizations_url": "https://api.github.com/users/octocat/orgs",
        "repos_url": "https://api.github.com/users/octocat/repos",
        "events_url": "https://api.github.com/users/octocat/events{/privacy}",
        "received_events_url": "https://api.github.com/users/octocat/received_events",
        "type": "User",
        "site_admin": false
      },
      "private": false,
      "html_url": "https://github.com/octocat/Hello-World",
      "description": "This your first repo!",
      "fork": false,
      "url": "https://api.github.com/repos/octocat/Hello-World",
      "archive_url": "https://api.github.com/repos/octocat/Hello-World/{archive_format}{/ref}",
      "assignees_url": "https://api.github.com/repos/octocat/Hello-World/assignees{/user}",
      "blobs_url": "https://api.github.com/repos/octocat/Hello-World/git/blobs{/sha}",
      "branches_url": "https://api.github.com/repos/octocat/Hello-World/branches{/branch}",
      "collaborators_url": "https://api.github.com/repos/octocat/Hello-World/collaborators{/collaborator}",
      "comments_url": "https://api.github.com/repos/octocat/Hello-World/comments{/number}",
      "commits_url": "https://api.github.com/repos/octocat/Hello-World/commits{/sha}",
      "compare_url": "https://api.github.com/repos/octocat/Hello-World/compare/{base}...{head}",
      "contents_url": "https://api.github.com/repos/octocat/Hello-World/contents/{+path}",
      "contributors_url": "https://api.github.com/repos/octocat/Hello-World/contributors",
      "deployments_url": "https://api.github.com/repos/octocat/Hello-World/deployments",
      "downloads_url": "https://api.github.com/repos/octocat/Hello-World/downloads",
      "events_url": "https://api.github.com/repos/octocat/Hello-World/events",
      "forks_url": "https://api.github.com/repos/octocat/Hello-World/forks",
      "git_commits_url": "https://api.github.com/repos/octocat/Hello-World/git/commits{/sha}",
      "git_refs_url": "https://api.github.com/repos/octocat/Hello-World/git/refs{/sha}",
      "git_tags_url": "https://api.github.com/repos/octocat/Hello-World/git/tags{/sha}",
      "git_url": "git:github.com/octocat/Hello-World.git",
      "issue_comment_url": "https://api.github.com/repos/octocat/Hello-World/issues/comments{/number}",
      "issue_events_url": "https://api.github.com/repos/octocat/Hello-World/issues/events{/number}",
      "issues_url": "https://api.github.com/repos/octocat/Hello-World/issues{/number}",
      "keys_url": "https://api.github.com/repos/octocat/Hello-World/keys{/key_id}",
      "labels_url": "https://api.github.com/repos/octocat/Hello-World/labels{/name}",
      "languages_url": "https://api.github.com/repos/octocat/Hello-World/languages",
      "merges_url": "https://api.github.com/repos/octocat/Hello-World/merges",
      "milestones_url": "https://api.github.com/repos/octocat/Hello-World/milestones{/number}",
      "notifications_url": "https://api.github.com/repos/octocat/Hello-World/notifications{?since,all,participating}",
      "pulls_url": "https://api.github.com/repos/octocat/Hello-World/pulls{/number}",
      "releases_url": "https://api.github.com/repos/octocat/Hello-World/releases{/id}",
      "ssh_url": "git@github.com:octocat/Hello-World.git",
      "stargazers_url": "https://api.github.com/repos/octocat/Hello-World/stargazers",
      "statuses_url": "https://api.github.com/repos/octocat/Hello-World/statuses/{sha}",
      "subscribers_url": "https://api.github.com/repos/octocat/Hello-World/subscribers",
      "subscription_url": "https://api.github.com/repos/octocat/Hello-World/subscription",
      "tags_url": "https://api.github.com/repos/octocat/Hello-World/tags",
      "teams_url": "https://api.github.com/repos/octocat/Hello-World/teams",
      "trees_url": "https://api.github.com/repos/octocat/Hello-World/git/trees{/sha}",
      "clone_url": "https://github.com/octocat/Hello-World.git",
      "mirror_url": "git:git.example.com/octocat/Hello-World",
      "hooks_url": "https://api.github.com/repos/octocat/Hello-World/hooks",
      "svn_url": "https://svn.github.com/octocat/Hello-World",
      "homepage": "https://github.com",
      "language": null,
      "forks_count": 9,
      "stargazers_count": 80,
      "watchers_count": 80,
      "size": 108,
      "default_branch": "master",
      "open_issues_count": 0,
      "is_template": true,
      "topics": [
        "octocat",
        "atom",
        "electron",
        "api"
      ],
      "has_issues": true,
      "has_projects": true,
      "has_wiki": true,
      "has_pages": false,
      "has_downloads": true,
      "archived": false,
      "disabled": false,
      "visibility": "public",
      "pushed_at": "2011-01-26T19:06:43Z",
      "created_at": "2011-01-26T19:01:12Z",
      "updated_at": "2011-01-26T19:14:43Z",
      "permissions": {
        "admin": false,
        "push": false,
        "pull": true
      },
      "allow_rebase_merge": true,
      "template_repository": null,
      "temp_clone_token": "ABTLWHOULUVAXGTRYU7OC2876QJ2O",
      "allow_squash_merge": true,
      "allow_auto_merge": false,
      "delete_branch_on_merge": true,
      "allow_merge_commit": true,
      "subscribers_count": 42,
      "network_count": 0,
      "license": {
        "key": "mit",
        "name": "MIT License",
        "url": "https://api.github.com/licenses/mit",
        "spdx_id": "MIT",
        "node_id": "MDc6TGljZW5zZW1pdA==",
        "html_url": "https://github.com/licenses/mit"
      },
      "forks": 1,
      "open_issues": 1,
      "watchers": 1
    },
    "author_association": "COLLABORATOR"
  }
]

 

이런 개발 방식에 익숙하지 않은 사람이라면 (정확히는 내가) 왜 번거로운 변환 과정을 직접 수행하는지,

왜 연관 없는 것처럼 보이는 상수로 매핑받는지를 이해할 수 없다

경제적인 관점으로 DB에서 저장할 바이트를 아끼기 위해 그럴 수도 있겠구나 싶다

빅 테크들은 어떻게 저장하는지를 본 적이 없어 이만 말을 줄여야겠다