Url Parsing in Scala

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

import java.net.URI
import scala.jdk.CollectionConverters._

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

    // Parse the URL and ensure there are no errors.
    val uri = URI.create(s)

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

    // UserInfo contains all authentication info; we need to split it
    // to get individual username and password.
    val userInfo = uri.getUserInfo
    println(userInfo)
    val Array(username, password) = userInfo.split(":")
    println(username)
    println(password)

    // The Host contains both the hostname and the port,
    // if present. We need to split them manually.
    println(uri.getHost + ":" + uri.getPort)
    println(uri.getHost)
    println(uri.getPort)

    // Here we extract the path and the fragment after
    // the #.
    println(uri.getPath)
    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.
    println(uri.getRawQuery)
    val queryParams = uri.getQuery.split("&")
      .map(_.split("="))
      .map(arr => arr(0) -> arr(1))
      .toMap
    println(queryParams)
    println(queryParams("k"))
  }
}

This Scala program demonstrates URL parsing using the java.net.URI class. Here’s a breakdown of what it does:

We start by importing necessary classes and methods.
We define our example URL string, which includes various components like scheme, authentication info, host, port, path, query parameters, and fragment.
We create a URI object from our string using URI.create(s).
We extract various components of the URL:
- Scheme using getScheme()
- User info using getUserInfo(), which we then split to get username and password
- Host and port using getHost() and getPort()
- Path using getPath()
- Fragment using getFragment()
- Query string using getRawQuery()
For query parameters, we split the query string and convert it into a Map for easy access.

To run this Scala program:

$ scala URLParsing.scala
postgres
user:pass
user
pass
host.com:5432
host.com
5432
/path
f
k=v
Map(k -> v)
v

This output shows all the different pieces that we extracted from the URL.

In Scala, we use the java.net.URI class which provides similar functionality to Go’s url.URL. However, some operations (like splitting the user info and parsing query parameters) need to be done manually in Scala.

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Url Parsing in Scala