http://www.bukkit.fr/index.php?/topic/9524-une-banque-a-emeraudes/

EmerauldBank.java

package fr.neatmonster.emerauldbank;

import org.bukkit.Bukkit;
import org.bukkit.ChatColor;
import org.bukkit.Material;
import org.bukkit.command.Command;
import org.bukkit.command.CommandSender;
import org.bukkit.entity.Player;
import org.bukkit.entity.Villager;
import org.bukkit.event.EventHandler;
import org.bukkit.event.Listener;
import org.bukkit.event.player.PlayerInteractEntityEvent;
import org.bukkit.inventory.ItemStack;
import org.bukkit.metadata.FixedMetadataValue;
import org.bukkit.plugin.java.JavaPlugin;

public class EmerauldBank extends JavaPlugin implements Listener {

    @Override
    public boolean onCommand(final CommandSender sender, final Command command, final String label, final String[] args) {
        if (!command.getName().equalsIgnoreCase("emerauldbank"))
            return false;
        if (!(sender instanceof Player))
            sender.sendMessage(ChatColor.RED + "This command is for players only!");
        else {
            final Player player = (Player) sender;
            if (args.length != 1 || !args[0].equalsIgnoreCase("deposit") && !args[0].equalsIgnoreCase("withdraw"))
                player.sendMessage(ChatColor.YELLOW + "Usage: /eb <withdraw/deposit>");
            else if (!player.hasPermission("emerauldsbank.create." + args[0].toLowerCase()))
                player.sendMessage(ChatColor.RED + "You're not allowed to use this command!");
            else {
                player.setMetadata("emerauldbank." + args[0].toLowerCase(), new FixedMetadataValue(this, null));
                player.sendMessage(ChatColor.GREEN + "Please select the villager you want to use.");
            }
        }
        return true;
    }

    @Override
    public void onEnable() {
        Bukkit.getPluginManager().registerEvents(this, this);
    }

    @SuppressWarnings("deprecation")
    @EventHandler
    public void onPlayerInteractEntity(final PlayerInteractEntityEvent event) {
        if (!(event.getRightClicked() instanceof Villager))
            return;
        final Player player = event.getPlayer();
        final Villager villager = (Villager) event.getRightClicked();
        final String name = villager.isCustomNameVisible() ? villager.getCustomName() : "";
        if (name != null && (name.equals("Deposit") || name.equals("Withdraw"))
                && !player.hasPermission("emerauldbank.use." + name.toLowerCase()))
            player.sendMessage(ChatColor.RED + "You're not allowed to interact with this villager.");
        else if (name != null && name.equals("Deposit")) {
            int count = 0;
            for (final ItemStack stack : player.getInventory().all(Material.EMERALD).values())
                count += stack.getAmount();
            player.getInventory().remove(Material.EMERALD);
            player.updateInventory();
            getConfig().set(player.getName(), getConfig().getInt(player.getName(), 0) + count);
            player.sendMessage(ChatColor.YELLOW + (count == 0 ? "No" : "" + count) + " emerauld(s) deposed.");
        } else if (name != null && name.equals("Withdraw")) {
            final int count = getConfig().getInt(player.getName(), 0);
            getConfig().set(player.getName(), 0);
            if (count > 0)
                player.getInventory().addItem(new ItemStack(Material.EMERALD, count));
            player.updateInventory();
            player.sendMessage(ChatColor.YELLOW + (count == 0 ? "No" : "" + count) + " emerauld(s) withdrawed.");
        } else {
            for (final String action : new String[] { "deposit", "withdraw" })
                if (player.hasMetadata("emerauldbank." + action)) {
                    villager.setCustomName(action.substring(0, 1).toUpperCase() + action.substring(1));
                    villager.setCustomNameVisible(true);
                    player.removeMetadata("emerauldbank." + action, this);
                    player.sendMessage(ChatColor.GREEN + "This villager now allows " + action + "s.");
                }
        }
    }
}

plugin.yml

name: EmerauldBank
version: 1.0
author: NeatMonster
main: fr.neatmonster.emerauldbank.EmerauldBank
commands:
  emerauldbank:
    aliases: [eb]