Url Parsing in CLIPS

Our URL parsing program demonstrates how to parse and extract information from a URL string in Java.

import java.net.URI;
import java.net.URISyntaxException;
import java.util.Arrays;
import java.util.Map;
import java.util.stream.Collectors;

public class URLParsing {
    public static void main(String[] args) {
        // We'll parse this example URL, which includes a
        // scheme, authentication info, host, port, path,
        // query params, and query fragment.
        String s = "postgres://user:pass@host.com:5432/path?k=v#f";

        try {
            // Parse the URL and ensure there are no errors.
            URI uri = new URI(s);

            // Accessing the scheme is straightforward.
            System.out.println(uri.getScheme());

            // UserInfo contains all authentication info; we need to split it
            // to get individual username and password.
            System.out.println(uri.getUserInfo());
            String[] userInfo = uri.getUserInfo().split(":");
            System.out.println(userInfo[0]);
            System.out.println(userInfo[1]);

            // The Host contains both the hostname and the port,
            // if present. We can access them separately.
            System.out.println(uri.getHost() + ":" + uri.getPort());
            System.out.println(uri.getHost());
            System.out.println(uri.getPort());

            // Here we extract the path and the fragment after the #.
            System.out.println(uri.getPath());
            System.out.println(uri.getFragment());

            // To get query params in a string of k=v format,
            // use getRawQuery(). You can also parse query params
            // into a map.
            System.out.println(uri.getRawQuery());
            Map<String, String> queryParams = Arrays.stream(uri.getQuery().split("&"))
                .map(param -> param.split("="))
                .collect(Collectors.toMap(param -> param[0], param -> param[1]));
            System.out.println(queryParams);
            System.out.println(queryParams.get("k"));

        } catch (URISyntaxException e) {
            e.printStackTrace();
        }
    }
}

Running our URL parsing program shows all the different pieces that we extracted.

$ javac URLParsing.java
$ java URLParsing
postgres
user:pass
user
pass
host.com:5432
host.com
5432
/path
f
k=v
{k=v}
v

This Java program uses the java.net.URI class to parse the URL. It provides methods to access various components of the URL. For query parameter parsing, we use Java 8 streams to split the query string and create a map.

Note that Java’s URI class handles the parsing slightly differently from Go’s url.Parse(). For example, it doesn’t provide a direct method to get the password, so we split the UserInfo string manually. Also, the query parameters are handled as a single string by default, so we implement custom parsing for demonstration purposes.

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Url Parsing in CLIPS