Exception from HttpRequest :

Exception in thread "main" java.lang.IllegalArgumentException: unsupported URI https://148-87-19-194_s-23-63-75-42_ts-1589834696-clienttons-s.akamaihd.net/eum/results.txt
at java.net.http/jdk.internal.net.http.common.Utils.newIAE(Utils.java:282)
at java.net.http/jdk.internal.net.http.HttpRequestBuilderImpl.checkURI(HttpRequestBuilderImpl.java:85)
at java.net.http/jdk.internal.net.http.HttpRequestBuilderImpl.uri(HttpRequestBuilderImpl.java:71)
at java.net.http/jdk.internal.net.http.HttpRequestBuilderImpl.uri(HttpRequestBuilderImpl.java:43)
at JavaHTTP/NetRequest.NetRequest.main(NetRequest.java:14)

Please use attached simplified java application "NetRequest.java" to re-produce the exception.

--Original Description--
To reproduce this, run HelloWebView with the attached file:

$ java HelloWebView file:///SOME-DIR/akamai.html

Then click on the "Click me" hyperlink. You will see the following exception:

Exception in thread "JavaFX Application Thread" java.lang.IllegalArgumentException: unsupported URI https://148-87-19-194_s-23-63-75-42_ts-1589834696-clienttons-s.akamaihd.net/eum/results.txt
        at java.net.http/jdk.internal.net.http.common.Utils.newIAE(Utils.java:282)
        at java.net.http/jdk.internal.net.http.HttpRequestBuilderImpl.checkURI(HttpRequestBuilderImpl.java:85)
        at java.net.http/jdk.internal.net.http.HttpRequestBuilderImpl.uri(HttpRequestBuilderImpl.java:71)
        at java.net.http/jdk.internal.net.http.HttpRequestBuilderImpl.uri(HttpRequestBuilderImpl.java:43)
        at javafx.web/com.sun.webkit.network.HTTP2Loader.<init>(HTTP2Loader.java:397)
        at javafx.web/com.sun.webkit.network.HTTP2Loader.create(HTTP2Loader.java:135)
        at javafx.web/com.sun.webkit.network.NetworkContext.fwkLoad(NetworkContext.java:166)
        at javafx.web/com.sun.webkit.network.URLLoaderBase.twkWillSendRequest(Native Method)
        at javafx.web/com.sun.webkit.network.HTTP2Loader.lambda$willSendRequest$14(HTTP2Loader.java:497)
        at javafx.web/com.sun.webkit.network.HTTP2Loader.lambda$callBackIfNotCanceled$10(HTTP2Loader.java:437)
        at javafx.graphics/com.sun.javafx.application.PlatformImpl.lambda$runLater$10(PlatformImpl.java:428)
        at java.base/java.security.AccessController.doPrivileged(AccessController.java:391)
        at javafx.graphics/com.sun.javafx.application.PlatformImpl.lambda$runLater$11(PlatformImpl.java:427)
        at javafx.graphics/com.sun.glass.ui.InvokeLaterDispatcher$Future.run(InvokeLaterDispatcher.java:96)
        at javafx.graphics/com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
        at javafx.graphics/com.sun.glass.ui.win.WinApplication.lambda$runLoop$3(WinApplication.java:174)
        at java.base/java.lang.Thread.run(Thread.java:832)

If I force the HTTP/1.x client there is no exception:

$ java -Dcom.sun.webkit.useHTTP2Loader=false HelloWebView file:///SOME-DIR/akamai.html

This might turn out to be a bug in the HTTP/2 client itself rather than WebView.