最も簡単な方法は
WebSession.get().getClientInfo().getUserAgent();
新しいWicketバージョン(6以降)では、以下を使用する必要があります。
WebClientInfo clientInfo = new WebClientInfo(getRequestCycle());
System.out.println("Client: " + clientInfo.getUserAgent());
System.out.println("Navigator: " + clientInfo.getProperties().getNavigatorAppName() + ", version " + clientInfo.getProperties().getNavigatorAppVersion() + ", codName: " + clientInfo.getProperties().getNavigatorAppCodeName() + ", plataform: " + clientInfo.getProperties().getNavigatorPlatform() + ", AppCodName: " + clientInfo.getProperties().getNavigatorAppCodeName());
System.out.println("NavigatorUserAgent: " + clientInfo.getProperties().getNavigatorUserAgent());
System.out.println("Tamanho da tela (Width x Height): " + clientInfo.getProperties().getScreenWidth() + " x " + clientInfo.getProperties().getScreenHeight() );