poniedziałek, 14 listopada 2016

Java - stop reading possibly huge xml once given element found

  Path versionFile = installationPath.resolve("large.xml");

  SAXParserFactory factory = SAXParserFactory.newInstance();
  SAXParser parser = factory.newSAXParser();

  InputStream is = openStream(versionFile);

  class BreakException extends SAXException {
   private String value = null;
   private static final long serialVersionUID = 1L;

  try {
   parser.parse(is, new DefaultHandler() {
    public void startElement(String uri, String localName, String qName, Attributes attributes) throws SAXException {
     if ("InstallType".equals(qName)) {
      String value = attributes.getValue("currentVersion");
      // really dirty way to break sax parsing on demand and return value out of anonymous handle by the way ;)
      BreakException breakException = new BreakException();
      breakException.value = value;
      throw breakException;
  } catch (BreakException be) {
   return be.value;

piątek, 19 sierpnia 2016

Ratpack And Spring Getting Started


Maven dependendencies


Spring initialization

public class WebConsoleConfiguration {

    public ServerConfigBuilder webServerConfig() {
        ServerConfigBuilder embedded = ServerConfig.embedded();
        return embedded;

    public RatpackServer webServer(ServerConfigBuilder config) throws Exception {
        RatpackServer server = RatpackServer.of(b -> b
                .registryOf(r -> r.add(String.class, "world"))
                .handlers(chain -> chain
                        .get("hello", ctx -> {
                            ctx.render(ctx.get(String.class) + " !");
                        .get("metrics", ctx -> {
        return server;


wtorek, 5 kwietnia 2016

git - stucked with modified files due to eol differences

Once you've got * text=auto set in your .gitattribute file all text files stored in repository will be changed into EOL sequence adequate to the host system. But any time checkouting on another system - all eols will be replaced with its specific. Quite nifty, isn't it?

But if for some reason your text file you've got in staging area contains for instance CRLF and you are working on linux machine - git status reporting it as modified. But you cannot reset this as there are no diff in terms of text=auto. Moreover git stash also seems to work badly, as again nothing to stash found. If you faced such a problem here is the solution

  1. Edit the .gitattribute file by commenting out the * text=auto line (with # sign)
  2. Type git status on the command line
  3. Revert .gitattribute file

środa, 24 lutego 2016

Hibernate - relation owner explained

Implementing bi-directional relationship is fairly easy whilst not very obvious for just off the boat hibernate users. Bi-directional relationship means you can navigate from one entity to the another and vice-versa. To do this you need mappedBy property. Lets say we have the following model.
  BrickSet owns many Bricks
  One Brick belongs to many BrickSet

@Table(name = "BrickSet")
public class BrickSet {
@ManyToMany(fetch=FetchType.Lazy, cascade= {CascadeType.ALL}
public Set getBricks() {
  return bricks;


czwartek, 14 stycznia 2016

Ubuntu - disappeared unity windows recovery guide

I found myself really confused that after some operations (eg. switching external displays around) I cannot activate opened applications. I suspected that those apps have to be somewhere on desktop, but apparently not in current view port. There have to be a way to grab and move them.. but how??

After a while of googling wmctrl nifty friend was on my toolbox ready for action.

Lets start from looking at options by typing wmctrl -h for displaying a help.
Now try to figure out what windows are on your desktop:

$ wmctrl -l
0x02e00002  0 krma-laptok XdndCollectionWindowImp
0x02e00005  0 krma-laptok unity-launcher
0x02e00008  0 krma-laptok unity-panel
0x02e0000b  0 krma-laptok unity-dash
0x02e0000c  0 krma-laptok Hud
0x0280000a  0 krma-laptok Desktop
0x0460000b  0 krma-laptok krma@krma-laptok: ~
0x044000b3  0 krma-laptok Inbox - Mozilla Thunderbird
0x0400053b  0 krma-laptok Java - Eclipse 

Lets look at the desktop present on our system
$ wmctrl -d
0  * DG: 3840x1080  VP: 0,0  WA: 45,24 3795x1056  N/A
But how to identify those that are out of viewport?
$ wmctrl -lG
0x02e00002  0 -3940 -1180 3840 1080 krma-laptok XdndCollectionWindowImp
0x02e00005  0 0    24   45   1056 krma-laptok unity-launcher
0x02e00008  0 0    0    1920 24   krma-laptok unity-panel
0x02e0000b  0 -1241 -740 1141 640  krma-laptok unity-dash
0x02e0000c  0 -1060 -164 960  64   krma-laptok Hud
0x0280000a  0 0    0    3840 1080 krma-laptok Desktop
0x0460000b  0 2101 114  1601 844  krma-laptok krma@krma-laptok: ~
0x044000b3  0 70   266  1294 629  krma-laptok Inbox - Mozilla Thunderbird
0x0400053b  0 7655 92   1860 988  krma-laptok Java - Eclipse
Eclipse's x position seems to be a little to high, isn't? Lets move it to (20,20) and leave existing size (1860,988) unchanged:
$ wmctrl -i -r 0x0400053b -e 0,20,20,-1,-1
PS. another nice tool is xdotool. It can
$ xdotool getwindowgeometry 0x0400053b
Window 67110203
  Position: 55,62 (screen: 0)
  Geometry: 1860x988
Note that position is different from (20,20) - moved (35,42)??

poniedziałek, 11 stycznia 2016

How to run javascript script in jvm environment?

Oracle's JDK8 comes with jjs command which runs javascript code agains nashorn build-in engine. Assumming the following piece of code
// script.js
var lines = `ls -lsa`.split("\n");
for each (var line in lines) {
          print("|> " + line);
After running it with the following command:
jjs -scripting script.js
We will be given with a nice listing of working directory