Boot 配置绑定与日志：让运行参数可解释

import java.util.*;
public class Main {
    record Settings(int pageSize, long timeoutMillis) {}
    static long positive(String text) {
        if (text.isEmpty()) throw new IllegalArgumentException("empty");
        long value=0;
        for (int i=0;i<text.length();i++) {
            char c=text.charAt(i);
            if (c<'0'||c>'9') throw new IllegalArgumentException("digit");
            // 每次累积都检查溢出，不能等绕回负数再判断。
            value=Math.addExact(Math.multiplyExact(value,10),c-'0');
        }
        if (value==0) throw new IllegalArgumentException("positive");
        return value;
    }
    static long duration(String text) {
        long factor; int suffix;
        if (text.endsWith("ms")) { factor=1; suffix=2; }
        else if (text.endsWith("s")) { factor=1000; suffix=1; }
        else if (text.endsWith("m")) { factor=60000; suffix=1; }
        else throw new IllegalArgumentException("unit");
        // 先换算为毫秒，再检查统一上界。
        long millis=Math.multiplyExact(positive(text.substring(0,text.length()-suffix)),factor);
        if (millis>120000) throw new IllegalArgumentException("range");
        return millis;
    }
    static Settings parse(Map<String,String> input) {
        if (!Set.of("page-size","request-timeout").containsAll(input.keySet()))
            throw new IllegalArgumentException("unknown key");
        long page=positive(input.getOrDefault("page-size","20"));
        if (page>200) throw new IllegalArgumentException("page range");
        long timeout=duration(input.getOrDefault("request-timeout","2s"));
        // 全部字段成功后才发布不可变配置。
        return new Settings((int)page,timeout);
    }
    static void eq(Object expected,Object actual) {
        if (!Objects.equals(expected,actual)) throw new AssertionError(actual);
    }
    static void reject(Runnable r) {
        try { r.run(); throw new AssertionError("accepted"); }
        catch (IllegalArgumentException | ArithmeticException expected) {}
    }
    public static void main(String[] args) {
        eq(new Settings(20,2000),parse(Map.of()));
        eq(new Settings(30,2000),parse(Map.of("page-size","30","request-timeout","2s")));
        eq(new Settings(200,120000),parse(Map.of("page-size","200","request-timeout","2m")));
        reject(()->parse(Map.of("request-timeout","3m")));
        reject(()->parse(Map.of("request-timeout","1000")));
        reject(()->parse(Map.of("page-size","0")));
        reject(()->parse(Map.of("page_size","20")));
        reject(()->parse(Map.of("request-timeout","999999999999999999999999s")));
        System.out.println("PASS 8 typed configuration tests");
    }
}