java.net.URI 获取带下划线的主机 [英] java.net.URI get host with underscores

问题描述

我对那个方法有一个奇怪的行为:

I got a strange behavior of that method:

导入 java.net.URI

    URI url = new URI("https://pmi_artifacts_prod.s3.amazonaws.com");
    System.out.println(url.getHost()); /returns NULL
    URI url2 = new URI("https://s3.amazonaws.com");
    System.out.println(url2.getHost());  //returns s3.amazonaws.com

`

我希望第一个 url.getHost() 是 pmi_artifacts_prod.s3.amazonaws.com，但它给了我 NULL.原来问题出在域名中的下划线，它是一个已知的错误，但仍然可以做些什么，因为我需要完全使用该主机?

i want first url.getHost() to be pmi_artifacts_prod.s3.amazonaws.com, but it gives me NULL. Turned out that problem is with underscores in domain name, its a known bug, but still what can be done as I need to work with this host exactly?

推荐答案

该错误不在 Java 中，而在于命名主机，因为下划线在主机名中不是一个有效字符.尽管被广泛错误地使用，Java 拒绝处理此类主机名.

The bug is not in Java but in naming the host, since an underscore is not a valid character in a hostname. Although widely used incorrectly, Java refuses to handle such hostnames.

https://en.wikipedia.org/wiki/Hostname#Restrictions_on_valid_hostnames

一种可能的解决方法:

public static void main(String...a) throws URISyntaxException, NoSuchFieldException, SecurityException, IllegalArgumentException, IllegalAccessException {
    URI url = new URI("https://pmi_artifacts_prod.s3.amazonaws.com");
    System.out.println(url.getHost()); //NULL


    URI uriObj = new URI("https://pmi_artifacts_prod.s3.amazonaws.com");
    if (uriObj.getHost() == null) {
        final Field hostField = URI.class.getDeclaredField("host");
        hostField.setAccessible(true);
        hostField.set(uriObj, "pmi_artifacts_prod.s3.amazonaws.com");
    }
    System.out.println(uriObj.getHost()); //pmi_artifacts_prod.s3.amazonaws.com


    URI url2 = new URI("https://s3.amazonaws.com");
    System.out.println(url2.getHost());  //s3.amazonaws.com
}

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