如何使用正则表达式获取此URL参数

Question

String url = "mysite.com/index.php?name=john&id=432"

How can I extract the id parameter (432)?

it can be in any position in the url and the length of the id varies too

Answer 1

You can use Apache URLEncodedUtils from HttpClient package:

import org.apache.http.NameValuePair;
import org.apache.http.client.utils.URLEncodedUtils;
import java.nio.charset.Charset;
import java.util.List;

public class UrlParsing {
    public static void main(String[] a){
        String url="http://mysite.com/index.php?name=john&id=42";
        List<NameValuePair> args= URLEncodedUtils.parse(url, Charset.defaultCharset());
        for (NameValuePair arg:args)
            if (arg.getName().equals("id"))
                System.out.println(arg.getValue());
    }
}

This print 42 to the console.

If you have the url stored in a URI object, you may find useful an overload of URLEncodedUtils.parse that accept directly an URI instance. If you use this overloaded version, you have to give the charset as a string:

URI uri = URI.create("http://mysite.com/index.php?name=john&id=42");
List<NameValuePair> args= URLEncodedUtils.parse(uri, "UTF-8");

Answer 2

I just give an abstract regex. add anything you don't want in id after [^&

Pattern pattern = Pattern.compile("id=([^&]*?)$|id=([^&]*?)&");

Matcher matcher = pattern.matcher(url);

if (matcher.matches()) {
    int idg1   = Integer.parseInt(matcher.group(1));
    int idg2   = Integer.parseInt(matcher.group(2));
}

either idg1 or idg2 has value.

Answer 3

您可以使用：

String id = url.replaceAll("^.*?(?:\\?|&)id=(\\d+)(?:&|$).*$", "$1");

Answer 4

The regex has already been given, but you can do it with some simple splitting too:

public static String getId(String url) {
        String[] params = url.split("\\?");
        if(params.length==2) {
                String[] keyValuePairs = params[1].split("&");
                for(String kvp : keyValuePairs) {
                        String[] kv = kvp.split("=");
                        if(kv[0].equals("id")) {
                                return kv[1];
                        }
                }
        }
        throw new IllegalStateException("id not found");
}