Welcome to the BukkitWiki!

This Wiki is home to Bukkit's documentation and regulations surrounding the Bukkit Project and it's services. Want to help out? We would love to have you! Signup to get started!

Plugin Tutorial/cz

From BukkitWiki
Jump to: navigation, search
TODOIcon.png
Working on it...

Tyto stránky se stále upravují...

Úvodem

Contents

Tento návod vám má pomoci při tvorbě nových pluginů. Z důvodu obsáhlosti není možné udělat kompletní návod a proto se tento návod zabývá pouze základy. Začíná se ověřením, zda-li rozumíte programovacímu jazyku Java, práci s IDE a programátorským rozhraním, a po kompletním zvládnutí tohoto návodu byste měli být schopni pokračovat bez pomoci dále.

Potřebné znalosti

Tyto návody potřebují alespoň základní znalost Javy. Pokud nevíte o Javě vůbec nic nebo minimum informací, tyto návody by vám také měli pomoci zábavnou formou pochopit principy Javy.

Video Java návody

  • PerwinCZ Návody na pluginy do Minecraftu od PerwinaCZ (česky).
  • iTechRemix Základní návody od iTechRemix (anglicky).
  • Thenewboston - Plno úžasných videí (anglicky).
  • JavaVideoTutes.com - Mnoho důležitých výukových videí Javy (anglicky).

Psané Java návody

Vývojové prostředí

Před tím, než se pustíte do zvládnutí Javy a tvorby pluginů, budete potřebovat nějaké vývojové prostředí - IDE (Integrated Development Environment). IDE je program který vám pomůže zkompilovat a zpracovat pluginy. Jsou tři nejpopulárnější vývojová prostředí: Eclipse, Netbeans, a IntelliJ IDEA. Eclipse je nejvíce populární mezi tvůrci pluginů do Minecraftu, zatímce IntelliJ je používán obecně programátory Javy. Pokud jste v Javě noví, doporučuji vám použít Eclipse, které nás bude v tomto návodu provázet.

Pro další informace navštiv Nastavení vývojového prostředí

Nový Plugin - projekt

Vytváříme projekt

Před začátkem si budete muset nastavit své vývojové prostředí. Zapněte Eclipse a vytvořte nový projekt kliknutím na File > New > Java Project:

NewJavaProject.png

Projekt pojmenujte jak chcete, a s průvodcem dokončete tvorbu projektu. Po levé straně se vám v seznamu vašich projektů zobrazí nová složka; Kliknutím na malou šipečku vedle jména složky se vám rozbalí všechny části vašeho projektu.

Připojení CraftBukkitu do projektu

Před začátkem programování pluginu si do svého projektu musíte připojit nejnovější verzi CraftBukkitu.

Poslední oficiální verzi stáhnete zde: Bukkit API - Development Snapshot


Pravým tlačítkem myši klikněte na jméno složky vašeho projektu a z rozbalovacího menu vyberte Properties. Dále vyberte Java Build Path z podmenu všech možností. Dále klikněte na Add External JARs, vyhledejte staženou verzi CraftBukkitu a vyberte ji do Eclipse. CraftBukkit by se vám měl v otevřeném okýnku zobrazit v seznamu. Když zavřete toto okýnko, a podíváte se doleva pod vaší rozkliknutou složku vašeho projektu, můžete si dále otevřít "Referenced Libraries" a v seznamu byste měli vidět CraftBukkit.

BuildPathPic.png

Bukkit Javadocs

JavaDocs je jakási knihovna informací o CraftBukkitu nebo celkově o Javě, všech metodách a jejich použití, které budete moci použít při tvorbě vašich pluginů. Pro Javu se souhrn těchto informací nachází zde: web Oracle. A zde je souhrn všech informací pro CraftBukkit: zde. Pokud chcete mít tyto informace vždy po ruce, když třeba přejedete myší přes nějaký název metody, tak si nejdříve klikněte na váš projekt v seznamu projektů vlevo pravým tlačítkem, vyberte "Properties" a dále v okně "Referenced Libraries" a pak vyberte "Properties". Vyberte "Javadoc Location" na levé straně okna které se otevře, a vložte adresu http://jd.bukkit.org/apidocs/ do textového pole pod "Javadoc URL". Mělo by to vypadat takto:

Bukkitjavadocs.png

Klikněte na ověření a poté na OK, a máte hotovo. Tímto jste spojili dokumentaci JavaDocs s vaším Eclipse projektem.

Vytváření balíčku

Nyní byste měli vytvořit "balíček", obsahující všechny Java třídy, které budete používat. Klikněte pravým tlačítkem myši na složku "src" a vyberte možnost "New package":

MakePackage.png

Balíček pojmenujte dle následujících 'pravidel':

  • Pokud máte doménu, pojmenujte balíček jako 'obrácené' doménové jméno.
    • Př.: Máte doménu "i_am_a_bukkit_developer.com" takže se váš balíček bude jmenovat "com.i_am_a_bukkit_developer" source
    • Nepoužívejte doménu, kterou nevlastníte.
  • Nevlastníte doménu? Zde jsou další možnosti:
    1. Vytvořte si účet na nějaké službě jako je GitHub nebo SourceForge
      • Pro GitHub postupujte následovně: here a máte subdoménu, takže se balíček může jmenovat com.github.mejmeno
    2. Použijte svoji mail adresu. Př.: "mejmeno@gmail.com" balíček bude "com.gmail.mejmeno"
    3. Poslední možnost. Prostě použijte unikátní jméno pro balíček. Tuto metodu však použijte jako na posledním místě.

Tady jsou jména blíčků, kterými nesmí začínat:

  • org.bukkit
  • net.bukkit
  • com.bukkit
  • net.minecraft

Jakmile máte jméno pro balíček, zakončete ho jménem pluginu. Když použijete např. svůj e-mail, celý balíček se bude jmenovat "com.gmail.mejmeno.mujplugin1"

Vytváříme hlavní třídu pluginu

Teď, když máme hotový set-up pluginu, můžeme začít vytvářet třídy pluginu a tvořit samotný plugin. Hlavní třídu pluginu vždy rozšiřuje JavaPlugin. Pouze jedinou třídu v pluginu může rozšiřovat JavaPlugin. Je dobré vytvořit hlavní třídu první a pojmenovat ji stejně jako plugin. Klikněte pravým tlačítkem na balíček, který jste předtím vytvořili, a vyberte možnost New Class. Když třídu otevřete, měli byste vidět něco jako toto:

package {$NejvyssiDomena}.{$Domena}.{$JmenoPluginu};

import org.bukkit.plugin.java.JavaPlugin;

public class {$JmenoPluginu} extends JavaPlugin {
    
}

Vytváření plugin.yml

Takže máme hotovou hlavní třídu našeho pluginu. Aby CraftBukkit 'viděl' hlavní třídu a vůbec 'věděl' o pluginu, musíme vytvořit soubor plugin.yml. Tento soubor bude obsahovat všechny informace o vašem pluginu, bez kterého se váš plugin neobejde!! Nyní klikněte pravým tlačítkem myši na soubor projektu, v žádném případě NE na složku "src". Vyberte New File. Pojmenujte soubor "plugin.yml", nijak jinak, a klikněte na OK. Eclipse vám soubor plugin.yml otevře ve vašem textovém editoru. (Nápověda: Pokud chcete mít vše dobře organizované, zavřete textový editor, a soubor plugin.yml přesuňte do workspacu(Doprava) a můžete ho editovat přímo v Eclipsu.) Jsou tu dvě věci, které do pluginu musíte dát; referenci vaší hlavní třídy a definování vašich příkazů. Asi nejběžnější plugin.yml vypadá takto:

name: {$JmenoPluginu}
main: {$JmenoBaliku}.{$HlavniTrida}
version: {$CisloVerze}

Poznámka: Jméno balíčku obsahuje jméno pluginu, tak nebuďte překvapeni, když uvidíte jméno pluginu dvakrát pod sebou! Vaše hlavní třída se buď ano, anebo nejmenuje jako váš plugin, takže se může stát, že jméno pluginu budetemít třikrát zapsané! A nezapomeňte, záleží na velkých i malých písmenech!

Nyní může být váš plugin načten Bukkitem, a budou to naznačovat zápisy v logu, ale nebude nic dělat!

onEnable() a onDisable()

Tyto metody jsou vyvolány, když se plugin zapne, nebo vypne. Za normálních okolností se plugin zapne, když jej načte server, abyste mohli zaregistrovat všechny potřebné události a provést nějaké další potřebné akce. onEnable() je metoda, která je vyvolána, když se plugin zapne a měla by obsahovat kód potřebný pro zavedení pluginu při zapínání. onDisable() je metoda provedená, když se plugin vypne a měla by obsahovat kód, který by měl pročistit dočasné věci uchovávané pluginem. Pluginy také mohou využít metodu onLoad(), aby provedli věci potřebné k provedení při načítání, ale

Úvod k onEnable() a onDisable()

Vytvořte metody onEnable() a onDisable() do třídy main vytvořené v minulé sekci. Bude to vypadat takto:

package {$HlavníDoména}.{$Doména}.{$NázevPluginu};

import org.bukkit.plugin.java.JavaPlugin;

public class {$NázevPluginu} extends JavaPlugin {
    
    @Override
    public void onEnable(){
        // Sem vložte logiky, které mají být provedeny během zapínání pluginu
    }
    
    @Override
    public void onDisable() {
        // Sem vložte logiky, které mají být provedeny během vypínání pluginu
    }
}

Tyto metody nyní existují, ale zatím nic nedělají.

Logging a message

A plugin can print a message to the console and the server log. It can accomplish this by invoking the correct method from the plugin's logger. First we must invoke the getLogger() method to retrieve the logger associate with this plugin. Then we can start logging.

We will write to the log when onEnable() method is called. We can do that by inserting the following line into the onEnable() method.

getLogger().info("onEnable has been invoked!");

You can then do the same inside onDisable(), making sure to change the message.

Your main class should now look something like this:

package {$TopLevelDomain}.{$Domain}.{$PluginName};

import java.util.logging.Logger;
import org.bukkit.plugin.java.JavaPlugin;

public class {$PluginName} extends JavaPlugin {
		
	public void onEnable(){
		getLogger().info("onEnable has been invoked!");
	}

	public void onDisable(){
		getLogger().info("onDisable has been invoked!");
	}
}

Listeners

Listeners are classes which implement org.bukkit.event.Listener and have methods that are executed in response to an event. For further details about listeners,

Please See: Event API Reference

Příkazy

The onCommand() Method

So, you now know how to register events and do something when they happen, but what if you only want something to happen when a command is typed? You use onCommand. This code is run whenever a player types a command preceded by the "/" character. E.g. typing "/do something" would call the onCommand method. In this case nothing would happen because no behaviour has been programmed.

Avoid using command names that are the same as those that come with Bukkit, and also consider carefully how unique your commands names will be. E.g. the "give" command is already used by several plugins, and if you implement yet another "give" command, your plugin will become incompatible with those other plugins. You must register your commands in the plugin's plugin.yml or they will not trigger this method.

The onCommand method must always return a boolean value - either true or false. If the value returned is true then you won't see any noticable events. However if it returns false then the plugin will revert to your plugin files' 'usage: property' and display a message to the user showing them how to use the command as specified in the plugin.yml file.

When using the onCommand you should always register 4 parameters.

  • CommandSender sender - who sent the command
  • Command cmd - the command that was executed
  • String commandLabel - the command alias that was used
  • String[] args - an array of additional arguments, e.g. typing /hello abc def would put abc in args[0], and def in args[1]

Setting up the command

public boolean onCommand(CommandSender sender, Command cmd, String label, String[] args){
	if(cmd.getName().equalsIgnoreCase("basic")){ // If the player typed /basic then do the following...
		// doSomething
		return true;
	} //If this has happened the function will return true. 
        // If this hasn't happened the a value of false will be returned.
	return false; 
}

When coding the onCommand function it is always good practice to return false at the very end of the function. Returning false will display the usage dialog set in plugin.yml (see below). This way if anything goes wrong the help message will be displayed. When returning a value the function will exit so if you return true any code underneath won't be run, unless a return statement is nested in a if statement or similar.

The .equalsIgnoreCase("basic") just means that it won't distinguish between upper and lower case characters. For example, the string "BAsIc" and "BasiC" would both equal basic and the code would be executed.

Adding your Command to the Plugin.yml

You will also need to add the command to your plugin.yml file. Add the following to the end of plugin.yml:

commands:
   basic:
      description: This is a demo command.
      usage: /<command> [player]
      permission: <plugin name>.basic
      permission-message: You don't have <permission>

  • basic - the name of the command.
  • description - the description of the command .
  • usage - the help dialog that users will see when you return false in the onCommand method. Write clearly, so that others can discern what the command is and how to use it.
  • permission - This is used by some help plugins to work out which commands to show to the user.
  • permission-message - This is output when the player attempts but does not have permission to use the command.

Note that yml files use 2 spaces for tabs, as the tab character will cause problems.

Console Commands vs. Player Commands

You may have noticed the CommandSender sender parameter above. CommandSender is a Bukkit interface which has two useful (for plugin writers) subclasses: Player and ConsoleCommandSender.

When you're writing your plugin, it's a very good idea to ensure that commands that can be run from the console actually work, and that commands that should only be run as a logged-in player really are only run as a logged-in player. Some plugins simply return if the sender is not a player (i.e. someone tried to use the plugin's commands from the console), even when those commands make perfect sense from the console (e.g. changing the weather on the server).

One way to do this is:

public boolean onCommand(CommandSender sender, Command cmd, String label, String[] args) {
	if (cmd.getName().equalsIgnoreCase("basic")){ // If the player typed /basic then do the following...
		// do something...
		return true;
	} else if (cmd.getName().equalsIgnoreCase("basic2")) {
		if (!(sender instanceof Player)) {
			sender.sendMessage("This command can only be run by a player.");
		} else {
			Player player = (Player) sender;
			// do something
		}
		return true;
	}
	return false;
}

In this example, the command basic can be run by anyone - a logged-in player, or the server operator on the console. But the command basic2 can only be run by logged-in players.

In general, you should allow as many commands as possible to work on both the console and for players. Commands that need a logged-in player can use the mechanism in the example above to check that the CommandSender is actually a player before continuing. Such commands would generally depend on some attribute of the player, e.g. a teleportation command needs a player to teleport, an item giving command needs a player to give the item to...

If you want to get more advanced, you could do some extra checks on your command arguments so that e.g. a teleportation command could be used from the console if and only if a player's name is also supplied.

Using a separate CommandExecutor class

The examples above just put the onCommand() method into the plugin's main class. For small plugins, this is fine, but if you're writing something more extensive, it may make sense to put your onCommand() method into its own class. Fortunately, this isn't too hard:

  • Create a new class within your plugin's package. Call it something like MyPluginCommandExecutor (although of course replacing MyPlugin with your plugin's actual name). That class must implement the Bukkit CommandExecutor interface.
  • In your plugin's onEnable() method, you need to create an instance of your new command executor class, and then make a call like getCommand("basic").setExecutor(myExecutor);, where "basic" is the command we want to handle, and myExecutor is the instance we created.

Best explained by example:

MyPlugin.java (the main plugin class):

@Override
public void onEnable() {
	// ...

	// This will throw a NullPointException if you don't have the command defined in your plugin.yml file!
	getCommand("basic").setExecutor(new MyPluginCommandExecutor(this));

	// ...
}

MyPluginCommandExecutor.java:

public class MyPluginCommandExecutor implements CommandExecutor {

	private MyPlugin plugin; // pointer to your main class, unrequired if you don't need methods from the main class

	public MyPluginCommandExecutor(MyPlugin plugin) {
		this.plugin = plugin;
	}

	@Override
	public boolean onCommand(CommandSender sender, Command cmd, String label, String[] args) {
		// implementation exactly as before...
	}
}

Notice how we pass an instance of the main plugin to the constructor for MyPluginCommandExecutor. This allows us easy access to the main plugin's methods if we need to.

By doing this, we can better organise our code - if the main onCommand() method is large and complex, it can be split into submethods without cluttering up the plugin's main class.

Note that if your plugin has multiple commands, you will need set the command executor for each command individually.

Writing a safe onCommand

When writing a onCommand, it's important that you don't assume any information, such as the sender being a Player. Things to keep in mind:

Make sure the sender is a Player before casting

Using simple code like this makes it possible:

public boolean onCommand(CommandSender sender, Command cmd, String label, String[] args){
	if (sender instanceof Player) {
           Player player = (Player) sender;
           // do something
        } else {
           sender.sendMessage("You must be a player!");
           return false;
        }
        // do something
        return false;
}

Check the arguments length

Don't always assume the sender typed the correct amount of arguments.

public boolean onCommand(CommandSender sender, Command cmd, String label, String[] args){
	if (args.length > 4) {
           sender.sendMessage("Too many arguments!");
           return false;
        } 
        if (args.length < 2) {
           sender.sendMessage("Not enough arguments!");
           return false;
        }
}

When getting another Player by their name, make sure they are online

Sometimes you want to get another player by the name entered by the player. Always make sure the player is online!

public boolean onCommand(CommandSender sender, Command cmd, String label, String[] args){
	Player target = (Bukkit.getServer().getPlayer(args[0]));
        if (target == null) {
           sender.sendMessage(args[0] + " is not online!");
           return false;
        }
        return false;
}

If you need to modify a Player currently not online, the OfflinePlayer class provides basic manipulation methods

Konfigurace/nastavení pluginu

The Bukkit API provides a convenient way for plugins to manage user configurable settings. Additionally it also serves as an easy way to store data.

Please see: Configuration API Reference

Práva

With the new Bukkit API for permissions, they couldn't be easier. To find out if a player has a particular permission use the following:

if(player.hasPermission("some.pointless.permission")) {
   //Do something
}else{
   //Do something else
}

You can also find if a permission has been set or not (equivalent to Java's null) with the following function:

boolean isPermissionSet(String name)

You may be wondering why there aren't any groups. The answer to that is because they aren't really needed. Previously one of the main uses for groups was to format chat messages. That however can be done just as easily with permissions. Inside your chat plugin's config you would define associations between permissions and prefixes. For example the permission "someChat.prefix.admin" would correspond to the prefix [Admin]. Whenever a player speaks with that permission their name will be prefixed with [Admin].

Another common usage might be to send a message to all users within a group. Again however this can be done with permissions with the following:

for(Player player: getServer().getOnlinePlayers()) {

    if(player.hasPermission("send.recieve.message")) {
        player.sendMessage("You were sent a message");
    }

}

Finally you may be asking, well how do I set and organise player's permissions if there are no groups? Although the bukkit API doesn't provide groups itself, you must install a permission provider plugin such as permissionsBukkit to manage the groups for you. This API provides the interface, not the implementation.

Configuring your permissions

If you want more control over your permissions, for example default values or children then you should consider adding them to your plugin.yml. This is completely optional, however it is advised. Below is an example permissions config that would be appended to the end of your existing plugin.yml:

permissions:
    doorman.*:
        description: Gives access to all doorman commands
        children:
            doorman.kick: true
            doorman.ban: true
            doorman.knock: true
            doorman.denied: false
    doorman.kick:
        description: Allows you to kick a user
        default: op
    doorman.ban:
        description: Allows you to ban a user
        default: op
    doorman.knock:
        description: Knocks on the door!
        default: true
    doorman.denied:
        description: Prevents this user from entering the door

Firstly, each permission your plugin uses is defined as a child node of the permissions node. Each permission can then optionally have a description, a default value, and children.

Defaults

By default when a permission isn't defined for a player hasPermission will return false. Inside your plugin.yml you can change this by setting the default node to be one of four values:

  • true - The permission will be true by default.
  • false - The permission will by false by default.
  • op - If the player is an op then this will be true.
  • not op - If the player is not an op then this will be true.

Children

Before now you will probably be used to the * permission to automatically assign all sub permissions. This has changed with the bukkit API and you can now define the child permissions. This allows for a lot more flexibility. Below is an example of how you do this:

permissions:
    doorman.*:
        description: Gives access to all doorman commands
        children:
            doorman.kick: true
            doorman.ban: true
            doorman.knock: true
            doorman.denied: false

Here the doorman.* permission has several child permissions assigned to it. The way child permissions work is when doorman.* is set to true, the child permissions are set to their values defined in the plugin.yml. If however doorman.* was set to false then all child permissions would be inverted.

Setting your own permissions

If you wish to know about developing your own permissions plugins (Ones that actaully set permissions) then check out the tutorial on Developing a permissions plugin.

Scheduling Tasks and Background Tasks

Currently, Minecraft servers operate nearly all of the game logic in one thread, so each individual task that happens in the game needs to be kept very short. A complicated piece of code in your plugin has the potential to cause huge delays and lag spikes to the game logic, if not handled properly.

Luckily, Bukkit has support for scheduling code in your plugin. You can submit a Runnable task to occur once in the future, or on a recurring basis, or you can spin off a whole new independent thread that can perform lengthy tasks in parallel with the game logic.

There is a separate Scheduler Programming tutorial which introduces the Scheduler, and gives more information on using it to schedule synchronous tasks, and on kicking off asynchronous tasks in Bukkit.

Manipulace s bloky

The easiest way to create blocks is to get an existing block and modify it. For example, if you want to change the block that is located five blocks above you, you would first have to get that block and then modify it. As an example  in reaction to a player move event:

public void onPlayerMove(PlayerMoveEvent evt) {
	Location loc = evt.getPlayer().getLocation();
	World w = loc.getWorld();
	loc.setY(loc.getY() + 5);
	Block b = w.getBlockAt(loc);
	b.setTypeId(1);
}

Going over this code we can see that it will change the block that is five blocks above the player to stone whenever the playerMove() event is triggered. Firstly we get the players location, then we get the world from the location. We then modify the co-ordinates of the location by adding five. Now that we have a location and the world we can create a block variable which will hold the block at the location. We get this by using the world and location in w.getBlockAt(loc);. Finally, we have the block at the location so we can change its ID or even its block data if we wanted to. Block data is specified by a byte so you would have to cast whatever value you set to a byte. For example in addition to the code above you could add b.setData((byte)3);

You can use this to generate buildings and individual blocks programmatically by the use of algorithms. For example to generate a solid cube we could simply make an algorithm with three nested for loops.

public void generateCube(Location loc, int length){  // public visible method generateCube() with 2 parameters point and location
	World world = loc.getWorld();

	int x_start = loc.getBlockX();     // Set the startpoints to the coordinates of the given location
	int y_start = loc.getBlockY();
	int z_start = loc.getBlockZ();
        /* Note: used getBlockX() instead of getX() because it returns an int value and avoid the cast with (int)loc.getX() */

	int x_length = x_start + length;    // now i set the lengths for each dimension... should be clear.
	int y_length = y_start + length;
	int z_length = z_start + length;

	for(int x_operate = x_start; x_operate <= x_length; x_operate++){ 
		// Loop 1 for the X-Dimension "for x_operate (which is set to x_start) 
		//do whats inside the loop while x_operate is 
		//<= x_length and after each loop increase 
		//x_operate by 1 (x_operate++ is the same as x_operate=x_operate+1;)
		for(int y_operate = y_start; y_operate <= y_length; y_operate++){// Loop 2 for the Y-Dimension
			for(int z_operate = z_start; z_operate <= z_length; z_operate++){// Loop 3 for the Z-Dimension

                                // get the block with the current coordinates
				Block blockToChange = world.getBlockAt(x_operate,y_operate,z_operate);
				blockToChange.setTypeId(34);    // set the block to Type 34
			}
		}
	}
}

This method will construct a 3D cube or cuboid with the given length and starting point. As for deleting blocks simply follow the same method for creating them but set the ID to 0 (air).

Manipulace s inventářem (hráče)

This section mostly covers player inventory manipulation, but the same applies to chest inventory manipulation as well if you find out how to get a chest's inventory :P. Here is a simple example of inventory manipulation:

public void onPlayerJoin(PlayerJoinEvent evt) {
    Player player = evt.getPlayer(); // The player who joined
    PlayerInventory inventory = player.getInventory(); // The player's inventory
    ItemStack itemstack = new ItemStack(Material.DIAMOND, 64); // A stack of diamonds
        
    if (inventory.contains(itemstack)) {
        inventory.addItem(itemstack); // Adds a stack of diamonds to the player's inventory
        player.sendMessage("Welcome! You seem to be reeeally rich, so we gave you some more diamonds!");
    }
}

So inside onPlayerJoin we first make a few variables to make our job easier: player, inventory and itemstack. Inventory is the player's inventory and itemstack is a ItemStack that has 64 diamonds. After that we check if the player's inventory contains a stack of diamonds. If the player has a stack of diamonds, we give him/her another stack with inventory.addItem(itemstack) and send a message. So inventory manipulation isn't actually that hard, if we wanted we could remove the stack of diamonds by simply replacing inventory.addItem(itemstack) with inventory.remove(itemstack) and change the message a little bit. Hopefully this helped!

Manipulace s věcmi

When dealing with items in the code, you use the ItemStack class for looking up and setting all information on that stack.

Enchantments

To enchant an item you must first know the Item Code and the Effect ID. Enchantments themselves cannot be instantiated (new Enchantment() won't work) because they're abstract, so you must use an EnchantmentWrapper. You can not enchant items which are not normally enchantable, on SMP because bukkit servers aren't set up to send enchantment information on not enchantable items. So no fire sticks.

int itemCode = 280;  //use the item code you want here
int effectId = 20;  //use the enchantment code you want here
int enchantmentLevel = 100;

ItemStack myItem = new ItemStack(itemCode);  //new item of item code
Enchantment myEnchantment = new EnchantmentWrapper(effectId);  //new enchantment of effect id
myItem.addEnchantment(myEnchantment, enchantmentLevel);  //enchant the item

Maps, and Sets, and Lists, Oh My!

Besides the Map/HashMap classes, Java offers many other data structures. They offer these different classes because there are times when a Map is not the most appropriate. Here's a separate page for discussing Java data structure classes in more detail.

HashMaps and How to Use Them

When making a plugin you will get to a point where just using single variables to state an event has happened or a condition has been met will be insufficient, due to more than one player performing that action/event.

This was the problem I had with one of my old plugins, Zones, now improved and re-named to Regions. I was getting most of these errors because I didn't consider how the plugin would behave on an actual server with more than one on at any given time. I was using a single boolean variable to check whether players were in the region or not and obviously this wouldn't work as the values for each individual player need to be separate. So if one player was in a region and one was out the variable would constantly be changing which could/would/did cause numerous errors.

A HashMap is an excellent way of doing this. A HashMap is a way of mapping/assigning a value to a key. You could set up the HashMap so that the key is a player and the value could be anything you want, however the useful things with HashMaps is that one key can only contain one value and there can be no duplicate keys. So say for example I put "adam" as the key and assigned a value of "a" to it. That would work as intended, but then say afterwards I wanted to assign the value of "b" to key "adam" I would be able to and would get no errors but the value of "a" assigned to key "adam" in the HashMap would be overwritten because HashMaps cannot contain duplicate values.

Defining a HashMap

public Map<Key, DataType> HashMapName = new HashMap<Key, Datatype>(); //Example syntax

//Example Declaration

public Map<Player, Boolean> pluginEnabled = new HashMap<Player, Boolean>();
public Map<Player, Boolean> isGodMode = new HashMap<Player, Boolean>();

Keep that code in mind because we will be using it for the rest of the tutorial on HashMaps. So, for example lets create a simple function which will toggle whether the plugin has been enabled or not. Firstly, inside your on command function which I explained earlier you will need to create a function to send the player name to the function and adjust the players state accordingly.

So inside on command you'll need this, the function name can be different but for the sake of simplicity it's best if you keep it the same.

Player player = (Player) sender;
togglePluginState(player);

This code above will cast the value of sender to player and pass that argument to the function togglePluginState(). But now we need to create our togglePluginState() function.

public void togglePluginState(Player player){
    
    if(pluginEnabled.containsKey(player)){
        if(pluginEnabled.get(player)){
            pluginEnabled.put(player, false);
            player.sendMessage("Plugin disabled");
        } else {
            pluginEnabled.put(player, true);
            player.sendMessage("Plugin enabled");
        }
    } else {
        pluginEnabled.put(player, true); //If you want plugin enabled by default change this value to false.
        player.sendMessage("Plugin enabled");
    }

}

Now, what this code is doing is checking if the HashMap first contains the key player, so if it has been put into the HashMap, if it is then we check the value of the HashMap key by get(player); if this is true then set value to false and send the player a message, else if the value is false then do the opposite, set the value to true and send a message again. But if the HashMap does not contain the key player then we can assume that this is their first run/use so we change the default value and add the player to the HashMap.

More Ideas for HashMaps

A HashMap (or really any kind of Map in Java) is an association. It allows quick and efficient lookup of some sort of value, given a unique key. Anywhere this happens in your code, a Map may be your solution.

Here are a few other ideas which are ideally suited to using Maps. As you will see, it doesn't have to be data that you store per player, but can be any kind of data that needs to be "translated" from one form to another.

Data Value Lookups
public Map<String, Integer> wool_colors = new HashMap<String, Integer>();

// Run this on plugin startup (ideally reading from a file instead of copied out row by row):
wool_colors.put("orange", 1);
wool_colors.put("magenta", 2);
wool_colors.put("light blue", 3);
   ..
wool_colors.put("black", 15);

// Run this in response to user commands - turn "green" into 13
int datavalue = 0;
if (wool_colors.containsKey(argument)) {
    datavalue = wool_colors.get(argument);
} else {
    try { datavalue = Integer.parseInt(argument); }
    catch (Exception e) { ; }
}

Saving/Loading a HashMap

Once you know how to work with HashMaps, you probably want to know how to save and load the HashMap data. Saving and loading HashMap data is appropriate if

  • you don't want an administrator to edit the data manually
  • you need to save data in binary format (too complex to organize for YAML)
  • you want to avoid parsing block names and/or other objects from freeform text

This is very simple way how to save any HashMap. You can replace HashMap<String, Integer> with any type of HashMap you want. Let's continue using the "pluginEnabled" HashMap defined from the previous tutorial. This code saves the given HashMap to the file with given path.

public void save(HashMap<String, Integer> map, String path)
{
	try
	{
		ObjectOutputStream oos = new ObjectOutputStream(new FileOutputStream(path));
		oos.writeObject(map);
		oos.flush();
		oos.close();
		//Handle I/O exceptions
	}
	catch(Exception e)
	{
		e.printStackTrace();
	}
}

// ...

save(pluginEnabled, getDataFolder() + File.separator + "example.bin");

You can see it's really easy. Loading works very very similar but we use ObjectInputStream instead of ObjectOutputStream ,FileInputStream instead of FileOutputStream,readObject() instead of writeObject() and we return the HashMap.

public HashMap<String, Integer> load(String path)
{
	try
	{
		ObjectInputStream ois = new ObjectInputStream(new FileInputStream(path));
		Object result = ois.readObject();
		//you can feel free to cast result to HashMap<String, Integer> if you know there's that HashMap in the file
		return (HashMap<String, Integer>)result;
	}
	catch(Exception e)
	{
		e.printStackTrace();
	}
}

// ...

String path = getDataFolder() + File.separator + "example.bin";
File file = new File(path);

if(file.exists()) // check if file exists before loading to avoid errors!
	pluginEnabled  = load(path);

You can use this "API" for saving/loading HashMaps, ArrayLists, Blocks, Players... and all Objects you know ;) . Please credit Tomsik68(the author of this) if you use this in your plugin/other project.

/** SLAPI = Saving/Loading API
 * API for Saving and Loading Objects.
 * You can use this API in your projects, but please credit the original author of it.
 * @author Tomsik68<tomsik68@gmail.com>
 */
public class SLAPI
{
	public static <T extends Object> void save(T obj,String path) throws Exception
	{
		ObjectOutputStream oos = new ObjectOutputStream(new FileOutputStream(path));
		oos.writeObject(obj);
		oos.flush();
		oos.close();
	}
	public static <T extends Object> T load(String path) throws Exception
	{
		ObjectInputStream ois = new ObjectInputStream(new FileInputStream(path));
		T result = (T)ois.readObject();
		ois.close();
		return result;
	}
}

Example implementation of this API: I'm skipping some part of code in this source

public class Example extends JavaPlugin {
	private ArrayList<Object> list = new ArrayList<Object>();
	public void onEnable()
	{
            try{
		list = SLAPI.load("example.bin");
            }catch(Exception e){
                //handle the exception
                e.printStackTrace();
            }
	}
	public void onDisable()
	{
            try{
		SLAPI.save(list,"example.bin");
            }catch(Exception e){
                 e.printStackTrace();
            }
	}
}

A minor note about this SLAPI and Java's ObjectOutputStream class. This will work un-modified if you are saving almost all well-known Java types like Integer, String, HashMap. This will work un-modified for some Bukkit types as well. If you're writing your own data object classes, and you may want to save their state using this technique, you should read up on Java's Serializable or Externalizable interface. The only difference between Externalizable and Serializable is, that Serializable automatically takes all of class's fields and tries to serialize them, while Externalizable allows you to define method for reading and writing the Object. It's easy to add to your code, and it will make your data persistent with very little work on your part. No more parsing!

Metadata

Bukkit is trying to make plugin development as easy as possible, so HashMaps with key of type Player, Entity, World or even a Block were replaced by Metadata. Metadata is some kind of alternative to HashMap. It allows you to add custom "fields" to Players, Entities, Worlds and Blocks. These things are all members of Metadatable class(check [1])It works very simply. Everything what is Metadatable holds its own HashMap of Metadata which you have access to. That means, if you're for example creating economy plugin, you need a HashMap of Player and Float or Double. With Metadata, you don't have to! You just attach to player new metadata value, and that's it!

Why to use Metadata

Metadata is all handled by Bukkit, what makes it very good alternative to HashMaps.

Metadata can be used to share info between plugins.

Why not to use Metadata

Slightly more difficult to get the value.

It is not saved on shutdown.

Getting & Setting Metadata

/* If you're having these methods in your plugin's main class (which extends JavaPlugin), you can remove parameters plugin from them,
 * and in the FixedMetadataValue constructor and getMetadata method, use "this" instead*/
public void setMetadata(Player player, String key, Object value, Plugin plugin){
  player.setMetadata(key,new FixedMetadataValue(plugin,value));
}
public Object getMetadata(Player player, String key, Plugin plugin){
  List<MetadataValue> values = player.getMetadata(key);  
  for(MetadataValue value : values){
     if(value.getOwningPlugin().getDescription().getName().equals(plugin.getDescription().getName())){
        return value.value();
     }
  }
}

Note: If you're manipulating with numbers, booleans or strings, use convenient method to get the result. For example, you can use asInt, asString or asBoolean instead of value to find out the value.

Databáze

Sometimes flat files aren't enough for what your looking to do, this is where databases come in. The most common database engines available on Linux/Mac/Windows machines typically run on some flavor of SQL (Structured Query Language).

Software offering SQL allow you to create databases with columns and header to identify to contents of each cell. Think of it as a spreadsheet on steroids, where every column you set up in your database can enforce rules to ensure integrity. Apart from being more organised than a simple custom data file, SQL provides faster access and better searching than flat files.

The SQL standard helps applications like Bukkit implement database storage for their data in a consistent way. Unfortunately, there's more than one SQL-ready database engine, and each has minor differences in how to configure and use it. Which one you choose may depend on your particular needs. (Some plugins even offer configurable options to connect to multiple database engines!)

SQLite

Alta189 has written a fantastic SQLite tutorial which I suggest you watch if you're interested in using SQL in your plugins, included with the tutorials is a handy library you can download and import to make using SQL easier. Once you have watched these video tutorials I would suggest you go and learn some SQL syntax, it's very straightforward and shouldn't take you long to pick up. SQL Tutorials @W3Schools and @1Keydata.

SQLite is great for very simple databases, because there's no server concerns to set up. Just make a few calls to create a new database and table. It's easy to back up: just copy the whole database file in one go. SQLite is a little bit weaker at data integrity, flexibility in data types, and it may not be something you would want to trust for huge databases of millions of rows. But for a new plugin in development, it's often easiest and fastest to get the SQL basics squared away with SQLite, even if you "graduate" to a more server-class database engine later.

MySQL

Another popular SQL database engine is called MySQL. It is closer to server-grade than SQLite, where many popular companies or websites depend on it for millions of webpage hits every day. With that security comes a little bit steeper learning-curve, because MySQL has more tunable parameters and capabilities.

The coding for plugins accessing MySQL is mostly the same as tiny SQLite or mega-sized Oracle, with only small differences in syntax here or there. But the administration has room to grow. You may want to set up accounts and privileges inside your MySQL setup. You may want to set up SQL scripts that organize your backups and rollback to previous states.

Vyvýjení vašeho pluginu

Once you have written your plugin, how do you get it from a collection of source files into a working jar file that can be installed on a server? First, set up a CraftBukkit server on your local machine. To do this, visit the wiki page on Setting up a server. Next you have to export your plugin to a .jar so that you can run it on your new server. To do this in Eclipse, click File > Export. In the window that pops up, under "Java", select "JAR file", and click next. You will see a window that looks like this:

Eclipse export

On the left, make sure that your src folder is selected. On the right, the two files beginning with a decimal point are to do with Eclipse and are not important to your plugin, so deselect them. It is vital that plugin.yml is selected in order for your plugin to work. Export your JAR file to any destination you like, but make sure you know where it is.

The jar file you have exported should now be a working plugin! Assuming of course that there are no errors in your code or your plugin.yml file. You can now drop the jar file you have exported into your bukkit server's "plugins" folder, reload or relaunch the server, and test away! In order to connect to a server running locally on your computer, simply put "localhost" as the IP address of the server in Minecraft multiplayer. If you run into errors that you can't solve for yourself, try visiting the plugin development forum, asking in the bukkitdev IRC channel, or re-reading this wiki. Once you have a useful working plugin, consider submitting your project to dev.bukkit for consumption by the Bukkit community.

Tipy a triky

Igniting the Player

The CraftBukkit API is capable of a lot of cool stuff. Here are some code snippets for some nice effects!

How to set someone on fire, in the context of a command:

public boolean onCommand(CommandSender sender, Command cmd, String label, String[] args){
    if(cmd.getName().equalsIgnoreCase("ignite")){
        Player s = (Player)sender;
        Player target = s.getServer().getPlayer(args[0]); // Gets the player who was typed in the command.
        // For instance, if the command was "/ignite notch", then the player would be just "notch".
        // Note: The first argument starts with [0], not [1]. So arg[0] will get the player typed.
        target.setFireTicks(10000);
        return true;
    }
    return false;
}

So if a player ran a command like /ignite Notch then if the player "Notch" was online, Notch would be set on fire!

Killing the player

To keep with the theme, here's a way to kill the player.

Use this for your onCommand method:

public boolean onCommand(CommandSender sender, Command cmd, String label, String[] args){
    if(cmd.getName().equalsIgnoreCase("KillPlayer")){
        Player target = sender.getServer().getPlayer(args[0]);
        target.setHealth(0); 
    }
    return false;
}

Here is an extension to that, that will kill the player with an explosion:

float explosionPower = 4F; //This is the explosion power - TNT explosions are 4F by default
Player target = sender.getWorld().getPlayer(args[0]);
target.getWorld().createExplosion(target.getLocation(), explosionPower);
target.setHealth(0);

Creating an Explosion

This code produces the TNT/Creeper Visual and Audio effects. This is useful if you are cancelling the TNT explode event but still want the effects.

	public void onExplosionPrime(ExplosionPrimeEvent event){
		
		Entity entity = event.getEntity();
		
		if (entity instanceof TNTPrimed){
			TNTPrimed tnt = (TNTPrimed) entity;
			event.getEntity().getWorld().createExplosion(tnt.getLocation(), 0);
			
		}
	}

Hiding player from other players

This will hide the command sender from specified player. Please note the command sender will only be hidden from specified player.

public boolean onCommand(CommandSender sender, Command cmd, String label, String[] args){
    if(cmd.getName().equalsIgnoreCase("HideMe") && args.length == 1){
        Player s = (Player)sender; //Gets the Sender
        Player target = sender.getServer().getPlayer(args[0]);  //Gets the player who is supposed not to see the sender
        target.hidePlayer(s);
        return true;
    }
    return false;
}

Striking thunders where player clicks

If you click a block with fishing rod, thunder will hit the clicked block. It's a simple and funny trick.

@EventHandler
    public void onPlayerInteractBlock(PlayerInteractEvent evt){
        if(evt.getPlayer().getItemInHand().getTypeId() == Material.FISHING_ROD.getId()){
            //maximal distance between player and thunder is 200 blocks
            evt.getPlayer().getWorld().strikeLightning(evt.getPlayer().getTargetBlock(null, 200).getLocation());
        }
    }

Request Section

http://forums.bukkit.org/forums/plugin-requests.13/

Example Files and Templates


If you have any more questions on this matter, don't hesitate to visit the BukkitDev IRC channel and ask!

Language   EnglishбеларускаяDeutschespañolsuomifrançaisitaliano한국어Nederlandsnorskpolskiportuguêsрусскийlietuviųčeština