Java 无法通过 URLConnection 或 HttpsURLConnection 访问 maven repo (403)

Purpose, just a POC (for now) to automatically and periodically find some CVE tags in the maven repository.

我可以通过浏览器和mvn很好地访问maven，但无法通过Java访问maven，我缺少什么？我try 过UrlConnection、HttpsURLConnection、有无GET、Content type、User Agent和Accept，对于我try 的所有地址，它总是返回403，同样的代码在其他网站(如"cve.mitre.org"或"nvd.nist.gov")上运行良好，但在以下情况下失败:https://mvnrepository.com/artifact/log4j/apache-log4j-extras/1.2.17".

我的URL是动态构建的，以"**https://mvnrepository.com/artifact/**""开头，然后添加组、名称和版本，将其转换为有效地址，如https://mvnrepository.com/artifact/log4j/apache-log4j-extras/1.2.17"

    System.setProperty("https.proxyHost", "xxxx");
    System.setProperty("https.proxyPort", "xxxx");

    String content = null;
    try {
        URL obj = new URL(address);
        HttpsURLConnection con = (HttpsURLConnection) obj.openConnection();
        con.setRequestMethod("GET");
        con.setRequestProperty("Content-Type", "application/json");
        con.setRequestProperty("User-Agent", "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/65.0.3325.181 Safari/537.36");
        con.setRequestProperty("Accept", "*/*");

        con.connect();
        
        BufferedReader br;
        
        if (con.getResponseCode() < 300) {
            br = new BufferedReader(new InputStreamReader(con.getInputStream(), StandardCharsets.UTF_8));
        } else {
            br = new BufferedReader(new InputStreamReader(con.getErrorStream(), StandardCharsets.UTF_8));
        }            

        final StringBuilder sb = new StringBuilder();
        String line;
        while ((line = br.readLine()) != null) {
            sb.append(line);
        }
        br.close();