20. パスが深い理由: 15階層を分解する

// 深いパスを / で分け、各段を「誰が決めたか」で分類して出す
import java.util.ArrayList;
import java.util.List;

class Main {
    record Part(String segment, String decidedBy) {}

    public static void main(String[] args) {
        String path = "repo/backend/order-service/src/main/java/"
                    + "jp/co/example/shop/order/application/service/impl/OrderServiceImpl.java";
        String sourceRoot = "src/main/java/";            // ビルドツール(Maven / Gradle)の規約
        // ファイルの1行目に書く package 宣言
        String packageName = "jp.co.example.shop.order.application.service.impl";
        String reverseDomain = "jp.co.example";          // example.co.jp を逆順にした接頭辞

        String[] seg = path.split("/");
        int rootStart = path.substring(0, path.indexOf(sourceRoot)).split("/").length;   // 3
        int pkgStart = rootStart + 3;
        int domainLen = reverseDomain.split("\\.").length;

        List<Part> parts = new ArrayList<>();
        for (int i = 0; i < seg.length; i++) {
            String who;
            if (i < rootStart)                     who = "team: repository / module split";
            else if (i < pkgStart)                 who = "build tool: source root convention";
            else if (i < pkgStart + domainLen)     who = "naming convention: reversed domain name";
            else if (i < pkgStart + domainLen + 2) who = "team: product / feature name";
            else if (i < seg.length - 1)           who = "team: layer naming habit";
            else                                   who = "Java: public class name = file name";
            parts.add(new Part(seg[i], who));
        }

        for (int i = 0; i < parts.size(); i++) {
            System.out.printf("%2d  %-22s %s%n", i + 1, parts.get(i).segment(), parts.get(i).decidedBy());
        }
        System.out.println();
        System.out.println("package declared in the file : " + packageName);
        // package 宣言の . を / に置き換えると、パスの 7〜14 段目になる
        System.out.println("package as a directory       : " + packageName.replace('.', '/'));
        System.out.println("segments in the path         : " + seg.length);
        System.out.println("segments that are the package: " + packageName.split("\\.").length);
        // 上の分類に Spring の枝は無い。決めた主体が Spring で始まる段を数えると 0 になる
        long bySpring = parts.stream().filter(p -> p.decidedBy().startsWith("Spring")).count();
        System.out.println("segments decided by Spring   : " + bySpring);
    }
}