Url Parsing in Squirrel

Here’s the translation of the Go URL parsing example to Java, formatted in Markdown suitable for Hugo:

Our URL parsing program demonstrates how to parse and extract information from URLs 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 u = new URI(s);

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

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

            // The Host contains both the hostname and the port,
            // if present. Use getHost() and getPort() to extract them.
            System.out.println(u.getHost() + ":" + u.getPort());
            System.out.println(u.getHost());
            System.out.println(u.getPort());

            // Here we extract the path and the fragment after
            // the #.
            System.out.println(u.getPath());
            System.out.println(u.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(u.getRawQuery());
            Map<String, String> queryParams = Arrays.stream(u.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 and manipulate URLs. It provides similar functionality to Go’s url.URL struct, allowing us to extract various components of a URL such as scheme, user info, host, port, path, query parameters, and fragment.

Note that Java’s URI class doesn’t provide direct methods for parsing query parameters into a map, so we’ve used Java streams to split the query string and collect it into a Map.

The structure and explanation closely follow the original, adapting the code to Java’s syntax and standard library. This example demonstrates how to work with URLs in Java, which is a common task in network programming and web development.

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