Solved NoClassDefFoundError using external API

Hi, I'm trying to use an external API in my plugin and I keep throwing this error, I've tried adding the .jar to a lib folder and also shading the classes but I can't get it to work, any ideas on where I went wrong?

 

@mysterypotatoguy

1. Treat the external API the same way you treat the Bukkit.jar (since the bukkit.jar is an api.)
2. Can you post the error? Can you post your current class?

 

Stacktrace:

Code:

[21:33:39 ERROR]: Error occurred while enabling DiscordBridge v1.0 (Is it up to date?)
java.lang.NoClassDefFoundError: sx/blah/discord/api/DiscordException
        at me.mysterypotatoguy.bukkithandler.BukkitHandler.onEnable(BukkitHandler.java:22) ~[?:?]
        at org.bukkit.plugin.java.JavaPlugin.setEnabled(JavaPlugin.java:291) ~[craftbukkit-1.9.jar:git-Bukkit-73eff0d]
        at org.bukkit.plugin.java.JavaPluginLoader.enablePlugin(JavaPluginLoader.java:332) [craftbukkit-1.9.jar:git-Bukkit-73eff0d]
        at org.bukkit.plugin.SimplePluginManager.enablePlugin(SimplePluginManager.java:404) [craftbukkit-1.9.jar:git-Bukkit-73eff0d]
        at org.bukkit.craftbukkit.v1_9_R1.CraftServer.loadPlugin(CraftServer.java:346) [craftbukkit-1.9.jar:git-Bukkit-73eff0d]
        at org.bukkit.craftbukkit.v1_9_R1.CraftServer.enablePlugins(CraftServer.java:318) [craftbukkit-1.9.jar:git-Bukkit-73eff0d]
        at net.minecraft.server.v1_9_R1.MinecraftServer.t(MinecraftServer.java:403) [craftbukkit-1.9.jar:git-Bukkit-73eff0d]
        at net.minecraft.server.v1_9_R1.MinecraftServer.l(MinecraftServer.java:368) [craftbukkit-1.9.jar:git-Bukkit-73eff0d]
        at net.minecraft.server.v1_9_R1.MinecraftServer.a(MinecraftServer.java:323) [craftbukkit-1.9.jar:git-Bukkit-73eff0d]
        at net.minecraft.server.v1_9_R1.DedicatedServer.init(DedicatedServer.java:241) [craftbukkit-1.9.jar:git-Bukkit-73eff0d]
        at net.minecraft.server.v1_9_R1.MinecraftServer.run(MinecraftServer.java:506) [craftbukkit-1.9.jar:git-Bukkit-73eff0d]
        at java.lang.Thread.run(Unknown Source) [?:1.8.0_73]
Caused by: java.lang.ClassNotFoundException: sx.blah.discord.api.DiscordException
        at java.net.URLClassLoader.findClass(Unknown Source) ~[?:1.8.0_73]
        at org.bukkit.plugin.java.PluginClassLoader.findClass(PluginClassLoader.java:77) ~[craftbukkit-1.9.jar:git-Bukkit-73eff0d]
        at org.bukkit.plugin.java.PluginClassLoader.findClass(PluginClassLoader.java:62) ~[craftbukkit-1.9.jar:git-Bukkit-73eff0d]
        at java.lang.ClassLoader.loadClass(Unknown Source) ~[?:1.8.0_73]
        at java.lang.ClassLoader.loadClass(Unknown Source) ~[?:1.8.0_73]
        ... 12 more

Classes:
BukkitHandler.java

Code:

package me.mysterypotatoguy.bukkithandler;

import me.mysterypotatoguy.discordhandler.DiscordHandler;
import me.mysterypotatoguy.discordhandler.PotatoBot;

import org.bukkit.Bukkit;
import org.bukkit.Color;
import org.bukkit.entity.Player;
import org.bukkit.event.EventHandler;
import org.bukkit.event.Listener;
import org.bukkit.event.player.AsyncPlayerChatEvent;
import org.bukkit.plugin.java.JavaPlugin;

import sx.blah.discord.api.DiscordException;
import sx.blah.discord.api.MissingPermissionsException;
import sx.blah.discord.util.HTTP429Exception;

public class BukkitHandler extends JavaPlugin implements Listener {
   
    @Override
    public void onEnable() {
        PotatoBot.login("redacted", "redacted");
    }
    @EventHandler
    public void onPlayerChat(AsyncPlayerChatEvent event) throws HTTP429Exception, DiscordException, MissingPermissionsException {
        Player player = event.getPlayer();
        String playername = player.getDisplayName();
        String message = event.getMessage();
        if (message.startsWith("!")) {
            message = message.replaceFirst("!", null);
            DiscordHandler.sendToDiscord(message, playername);
        }
    }
    public static void sendToMinecraft(String userB, String messageB) {
        for(Player player : Bukkit.getOnlinePlayers()) {
            player.sendMessage(Color.AQUA + "[Discord] " + userB + ":" + messageB);       
        }
    }
}

DiscordHandler.java

Code:

package me.mysterypotatoguy.discordhandler;

import me.mysterypotatoguy.bukkithandler.BukkitHandler;
import sx.blah.discord.api.DiscordException;
import sx.blah.discord.api.MissingPermissionsException;
import sx.blah.discord.handle.EventSubscriber;
import sx.blah.discord.handle.impl.events.MessageReceivedEvent;
import sx.blah.discord.handle.impl.events.ReadyEvent;
import sx.blah.discord.handle.obj.IChannel;
import sx.blah.discord.handle.obj.IMessage;
import sx.blah.discord.handle.obj.IUser;
import sx.blah.discord.util.HTTP429Exception;
import sx.blah.discord.util.MessageBuilder;

public class DiscordHandler {
    @EventSubscriber
    public void onReadyEvent(ReadyEvent event) {
        //Connect to server
    }
    public void onMessageReceive(MessageReceivedEvent event) {
        IMessage message = event.getMessage();
        IChannel channel = message.getChannel();
        IUser user = message.getAuthor();
        String userB = user.getName().toString();
        String messageB = message.toString();
        if(channel.getName() == "Minecraft") {
            BukkitHandler.sendToMinecraft(userB, messageB);
        }
    }
    public static void sendToDiscord(String message, String playername) throws HTTP429Exception, DiscordException, MissingPermissionsException {
            new MessageBuilder(PotatoBot.client).appendContent(playername + ": "  + message).withChannel("Minecraft").build();
    }
}

PotatoBot.java:

Code:

package me.mysterypotatoguy.discordhandler;

import sx.blah.discord.api.ClientBuilder;
import sx.blah.discord.api.DiscordException;
import sx.blah.discord.api.IDiscordClient;
import sx.blah.discord.handle.EventDispatcher;

public class PotatoBot {
    private String moduleName = "PotatoBot";
    private String moduleVersion = "1.0";
    private String moduleMinimumVersion = "2.3.1";
    private String author = "Mysterypotatoguy";
    public static IDiscordClient client;
   
    @SuppressWarnings("static-access")
    public PotatoBot(IDiscordClient client) {
        this.client = client;
    }
   
    public static PotatoBot login(String email, String password) {
        PotatoBot bot = null;
       
        ClientBuilder builder = new ClientBuilder();
        builder.withLogin(email, password);
        try {
            IDiscordClient client = builder.login();
            bot = new PotatoBot(client);
        } catch (DiscordException e) {
            e.printStackTrace();
        }
        return bot;
    }

    public void disable() {
        //Don't need to do anything here
    }

    public boolean enable(IDiscordClient client) {
        EventDispatcher dispatcher = client.getDispatcher();
        dispatcher.registerListener(new DiscordHandler());
        return true;
    }

    public String getAuthor() {
        return author;
    }

    public String getMinimumDiscord4JVersion() {
        return moduleMinimumVersion;
    }

    public String getName() {
        return moduleName;
    }

    public String getVersion() {
        return moduleVersion;
    }
   
}

Also pom.xml:

Code:

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
  <modelVersion>4.0.0</modelVersion>
  <groupId>me.mysterypotatoguy.discordbridge</groupId>
  <artifactId>DiscordBridge</artifactId>
  <version>1.0</version>
  <description>Plugin for bridging Discord and Minecraft</description>
   <build>
      <plugins>
          <plugin>
              <groupId>org.apache.maven.plugins</groupId>
              <artifactId>maven-shade-plugin</artifactId>
              <executions>
                  <execution>
                      <phase>package</phase>
                      <goals>
                          <goal>shade</goal>
                      </goals>
                      <configuration>
                          <createDependencyReducedPom>false</createDependencyReducedPom>
                          <minimiseJar>true</minimiseJar>
                          <artifact>
                              <includes>
                                  <include>io.github.austinv11:Discord4J</include>
                              </includes>
                          </artifact>
                      </configuration>
                  </execution>
              </executions>
          </plugin>
            <plugin>
                  <artifactId>maven-assembly-plugin</artifactId>
                  <configuration>
                    <archive>
                      <manifest>
                        <mainClass>me.mysterypotatoguy.bukkithandler.BukkitHandler</mainClass>
                      </manifest>
                        </archive>
                    <descriptorRefs>
                         <descriptorRef>jar-with-dependencies</descriptorRef>
                    </descriptorRefs>
                  </configuration>
            </plugin>
      </plugins>
   </build>  
   <repositories>
     <repository>
         <id>spigot-repo</id>
         <url>https://hub.spigotmc.org/nexus/content/repositories/snapshots/</url>
     </repository>
     <repository>
         <id>jitpack.io</id>
         <url>https://jitpack.io</url>
      </repository>
</repositories>
<dependencies>
     <!--Spigot API-->
     <dependency>
            <groupId>org.spigotmc</groupId>
            <artifactId>spigot-api</artifactId>
            <version>1.9-R0.1-SNAPSHOT</version>
            <scope>provided</scope>
     </dependency>
     <!--Bukkit API-->
     <dependency>
             <groupId>org.bukkit</groupId>
             <artifactId>bukkit</artifactId>
             <version>1.9-R0.1-SNAPSHOT</version>
             <scope>provided</scope>
     </dependency>
     <dependency>
            <groupId>com.github.austinv11</groupId>
            <artifactId>Discord4J</artifactId>
            <version>dev-SNAPSHOT</version>
            <scope>provided</scope>
     </dependency>
</dependencies>
</project>

Apologies for the poor code, it's a rough draft until I can get something that at least semi-works

 

@mysterypotatoguy

You have to actually shade it and say that it is exported. Maven does not include things like that in jars by default.

If you actually look in your jarfile, you will find it is missing.

 

Have I not shaded it correctly? how would I say it is exported?
I have also noticed that the jarfile is empty and no matter what I try I cannot get anything to package with the classes

 

@mysterypotatoguy

Your entire plugin is empty?

 

Yeah I worded that wrong didn't I...
the .jar has the classes I wrote, plugin.yml, pom.xml etc but it doesn't have the discord libraries it needs because they aren't exporting

 

@mysterypotatoguy

There you go. Look into "maven shading"

 

I've already tried shading (though I'm not sure how successfully).
Eclipse lists maven dependencies in the file manager but i think the problem is that they aren't being exported

 

@mysterypotatoguy

Not successfully, considering they weren't shaded.

 

@mythbusterma

Could you point me to which part of my pom is wrong? I really cannot find a way to get this to work

 

@mysterypotatoguy

Look at this repo for an example of correctly shading:

github.com/tridentsdk/tridentsdk

 

I really cannot find a way to get this to work. Using maven I can create a shaded jar but not one with plugin.yml or pom.xml in...
The maven dependencies just aren't exporting with the jar and I can't find a way to make it work

any advice?

 

If the API is a plugin on it's own (Like how BKCommonLib is treated as a plugin) make sure to depend your plugin on the API.

http://wiki.bukkit.org/Plugin_YAML (depend)

 

@adgdeveloping

No, it's not.


@mysterypotatoguy

Show us the updated pom.xml

 

Call me old-school if you want, but why don't you just add the classes manually to the jar?
@mysterypotatoguy

 

Pom:

Code:

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
  <modelVersion>4.0.0</modelVersion>
  <groupId>me.mysterypotatoguy.discordbridge</groupId>
  <artifactId>DiscordBridge</artifactId>
  <version>1.0</version>
  <description>Plugin for bridging Discord and Minecraft</description>
  <packaging>jar</packaging>
  <name>DiscordBridge[1.0]</name>
   <build>
      <plugins>
          <plugin>
              <groupId>org.apache.maven.plugins</groupId>
              <artifactId>maven-compiler-plugin</artifactId>
              <version>3.1</version>
              <configuration>
                  <source>1.7</source>
                  <target>1.7</target>
              </configuration>
          </plugin>
          <plugin>
              <groupId>org.apache.maven.plugins</groupId>
              <artifactId>maven-shade-plugin</artifactId>
              <version>2.4.3</version>
              <configuration>
              </configuration>
              <executions>
                  <execution>
                      <phase>package</phase>
                      <goals>
                          <goal>shade</goal>
                      </goals>
                  </execution>
              </executions>
          </plugin>
      </plugins>
   </build>
   <repositories>
     <repository>
         <id>spigot-repo</id>
         <url>https://hub.spigotmc.org/nexus/content/repositories/snapshots/</url>
     </repository>
     <repository>
         <id>jitpack.io</id>
         <url>https://jitpack.io/</url>
      </repository>
</repositories>
<dependencies>
     <!--Spigot API-->
     <dependency>
            <groupId>org.spigotmc</groupId>
            <artifactId>spigot-api</artifactId>
            <version>1.9-R0.1-SNAPSHOT</version>
            <scope>provided</scope>
     </dependency>
     <!--Bukkit API-->
     <dependency>
             <groupId>org.bukkit</groupId>
             <artifactId>bukkit</artifactId>
             <version>1.9-R0.1-SNAPSHOT</version>
             <scope>provided</scope>
     </dependency>
     <dependency>
            <groupId>com.github.austinv11</groupId>
            <artifactId>Discord4J</artifactId>
            <version>dev-SNAPSHOT</version>
            <classifier>shaded</classifier>
            <scope>compile</scope>
     </dependency>
    </dependencies>
</project>

@Konato_K surprisingly this worked... makes me question why eclipse won't do this on export

 

Signature 8. point

 

Marked as solved, but if anyone knows how to do this the non-hacky way then it would be appreciated

 

@mysterypotatoguy
Maven is the non hacky way.

 

Well, that didn't seem to work

 

@mysterypotatoguy I don't use maven so I don't know what could be wrong with your pom, but try looking into examples and see what the libraries aren't shading, until you figure out I guess placing the classes manually is the way to go.