Java 8获取没有最后一个段的完整URL路径（带或不带尾部斜杠）

Question

I have URLs as below and need to trim them as follows without the last segment. There may or may not be a trailing slash.

localhost:8080/myapp -> localhost:8080/

https://myapp-dev.myhost.com/app/ -> https://myapp-dev.myhost.com/

https://myapp-dev.myhost.com/app/app2 -> https://myapp-dev.myhost.com/app/

Of course I could try solutions like

String[] tokens = uri.split("/"); // then concatenate previous ones...

or

Path path = Paths.get(uri.getPath());
String secondToLast = path.getName(path.getNameCount() - 2).toString();

But isn't there some more robust utility or method?

Answer 1

Try passing the url string into a URL object and then pulling out the required segments:

URL someURL = new URL("https://myapp-dev.myhost.com/app/");
System.out.println("PATH = " + someURL.getPath());
System.out.println("HOST = " + someURL.getHost());
System.out.println("PROTOCOL = " + someURL.getProtocol());
System.out.println("PORT = " + someURL.getPort());

output:

PATH = /app/

HOST = myapp-dev.myhost.com

PROTOCOL = https

PORT = 8080

Answer 2

If all you need is to trim everything after the last "/" (or the second last if the string ends with "/") may be a simple function could solve this:

public static void main(String[] args){ 

    Function<String,String> trimUrlString = s -> { 
        s = s.endsWith("/") ? s.substring(0, s.length()-1) : s;
        return  s.substring(0, s.lastIndexOf('/')+1);
    };

    String u1 = "localhost:8080/myapp";        
    System.out.println(trimUrlString.apply(u1));
    String u2 = "https://myapp-dev.myhost.com/app/";     
    System.out.println(trimUrlString.apply(u2));        
}
//output: localhost:8080/      https://myapp-dev.myhost.com/

EDIT

Another aproach which might be shorter is to chain two replaceAll calls :

myString.replaceAll("/$", "").replaceAll("/[^/]+$", "/");

The first call will remove a forward slash at the end if any, if there is no slash at the end myString remains the same. The second call will then replace every char after the last / which is not a /

Some test cases with your examples:

    String[] urls = {"localhost:8080/myapp",
                     "https://myapp-dev.myhost.com/app/test.pdf",
                     "http://myapp-dev.host.com/app/", 
                     "http://app.host.com:8080/app/app2"};

    for(String url : urls){
        String s = url.replaceAll("/$", "").replaceAll("/[^/]+$", "/");
        System.out.println(url);
        System.out.println(s); 
        System.out.println();
    }

Answer 3

You can split the string using a regular expression as I have mentioned in the comment. I provide below the Regex.

^https?:\/\/\w+(:[0-9]*)?(\.\w+)?

You can try with the following examples.

https://mydomain:8080

http://localhost:8090

You can also verify in https://rubular.com/ by pasting the regular expression and the example strings.

Answer 4

Use String.lastIndexOf and String.substring to strip off last component.

Something like:

private String stripLastComponent(String path) {
    int n = path.lastIndexOf('/');
    if(n < 0) { // no / in path
        return path;
    }
    String stripped = path.substring(0, n);
    if(n == path.length()) { // '/' was last char, so try stripping again
        stripped = stripLastComponent(stripped);
    }
    return stripped;
}