Tutorial Properly use the PlayerCommandPreprocessEvent

Discussion in 'Resources' started by teej107, Dec 27, 2014.

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    teej107

    I started to see too many of these posts involving the PlayerCommandPreprocessEvent and they are using it badly. So I am making this resource so I don't repeat myself over and over again like a crazy person and on the behalf of @SuperOriginal.

    JavaDoc link to PlayerCommandPreprocessEvent

    Whether you want to block a command or change the outcome, this thread applies to every usage of the event.

    ____________________________________________________________
    Steps
    1. Get the message (of course)
    2. Split the String message by whitespaces.
      Code:
      String[] array = message.split(" "); //Single whitespace
    3. Perform the right checks for your desired outcome
      Code:
      if(array[0].equalsIgnoreCase("/command")
      {
          //Your code here
      }
    Other important info:
    _____________________________________________________________________________
    Example
    If you wanted to override/block a command such as /heal <player>, these would be the steps to use.

    Code:
    @EventHandler
    public void onCommandPreprocess(PlayerCommandPreprocessEvent event)
    {
        //Just establishing a context
        // All further code will go inside this method
    }
    1. Code:
      String message = event.getMessage(); // Getting the message
    2. Code:
      String[] array = message.split(" ");
      //Splitting the message
    3. Code:
      //Performing the right checks.
      if(array.length == 2)
      {
          if(array[0].equalsIgnoreCase("/heal") && array[1].equals("teej107"))
          {
              event.setCancelled(true);
              event.getPlayer().sendMessage("Game too hard for ya?");
          }
      }
    _____________________________________________________________________________
    The don'ts and whys
    1. Check the command message directly using .equals() or String#startsWith().​
    a. "/thisCommand" does not equal "/THISCommand" when using .equals(). Players can easily bypass your check.

    b. By checking to see if the message startsWith() a certain String, you are literally changing the outcome of all commands that start with the given String. If you want to change the "/op" command with startsWith(), you are changing commands such as "/open" or "/optimize" which you may not want.
    2.
    To save your self from developing a useless plugin, make sure you revoke the right permissions from the players. I've seen many questions about trying to block the /pl command and its aliases. The best way in that
    scenario is to revoke the permission bukkit.command.plugins as said here: http://wiki.bukkit.org/CraftBukkit_Commands#Additional_Permissions

    3.


    That's it for the tutorial! If you think I forgot something, say so. If I made a dumb mistake with the writing, speak up so we don't have to deal with bad tutorials in the resources section.


     
    Last edited: Oct 28, 2015
  2. Offline

    SuperOriginal

    Thank you! ;)
     
    teej107 likes this.
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    Experminator

    @teej107 Nice tutorial. A little bit easy, but super useful for beginners!
    I speak for all: Thank you!
     
    teej107 likes this.
  4. Offline

    To175

    I just want to block /command:something :|
     
  5. Offline

    teej107

    Ah yes, let me add something in about that.
     
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    To175

    @teej107
    Haha ok thanks you sooo much :)

    Sorry :p I splitt with ":" ^^' :p
    too lazy today... to much noobs killed me :x
     
    Last edited: Dec 27, 2014
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    Cirno

    Don't forget to add that this is not the way to make commands; I've seen a lot of people use this event to make commands, which is rude because they usually cancel the event and leave any other plugins that use that command useless
     
    teej107 likes this.
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    xTrollxDudex

    Not that I would want to clean up after somebody else's command if they're doing that.
     
  9. Offline

    ChipDev

    Could be helpful to give your plugin DA POWA and have all other plugins cancelled. Think about it ^^)
     
  10. Offline

    teej107

    Jerk plugin right there. It won't have much power when I uninstall it!
     
  11. Offline

    ChipDev

    Cancel all commands >;D
     
  12. Offline

    AdamQpzm

    @teej107 Your tutorial kinda contradicts itself now - it starts to guide someone how to block a command (example used, /heal) but then goes on to suggest revoking the permission when someone brings up the /essentials:heal system... what was the point of the blocking of /heal, then? :p

    Other than that, a good enough tutorial. Now if only the people that needed to read this did. Hopefully we'd have less /pl blocking plugins. Or at least better made ones.
     
  13. Offline

    teej107

    @AdamQpzm /heal was just an example. If there is a better command out there that would be better suited, tell me.
     
  14. Offline

    AdamQpzm

    @teej107 Imo, none of them :p As your post says, negating the permission works. It's clearly the superior way of absolute blocking. Only reason to block with preprocess is for custom criteria (i.e. cooldown, disabled for certain targets, etc)
     
    timtower and teej107 like this.
  15. Offline

    RingOfStorms

    What if an author didn't add permissions to a command :3
     
  16. Offline

    AdamQpzm

    @RingOfStorms Shun the author? :p Well, fair point I suppose. For "custom criteria", or for cleaning up someone else's mess.
     
  17. Offline

    bwfcwalshy Retired Staff

    Nice tutorial for the beginners.
     
  18. Offline

    Hex_27

    Would use this <3 Thanks
     
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