Morphia - Class not found defined in dbObj

Question

I'm having a rather interesting issue. When attempting to load a model from a Mongo instance, Morphia throws the following error:

[22:17:13 WARN]: Class not found defined in dbObj: 
java.lang.ClassNotFoundException: me.mattrick.test.storage.TestStat
    at java.net.URLClassLoader.findClass(URLClassLoader.java:381) ~[?:1.8.0_101]
    at java.lang.ClassLoader.loadClass(ClassLoader.java:424) ~[?:1.8.0_101]
    at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:331) ~[?:1.8.0_101]
    at java.lang.ClassLoader.loadClass(ClassLoader.java:357) ~[?:1.8.0_101]
    at java.lang.Class.forName0(Native Method) ~[?:1.8.0_101]
    at java.lang.Class.forName(Class.java:348) ~[?:1.8.0_101]
    at org.mongodb.morphia.mapping.DefaultCreator.getClass(DefaultCreator.java:175) [Test-1.5-SNAPSHOT-shaded.jar:?]
    at org.mongodb.morphia.mapping.DefaultCreator.createInstance(DefaultCreator.java:97) [Test-1.5-SNAPSHOT-shaded.jar:?]
    at org.mongodb.morphia.mapping.EmbeddedMapper.readMapOrCollectionOrEntity(EmbeddedMapper.java:205) [Test-1.5-SNAPSHOT-shaded.jar:?]
    at org.mongodb.morphia.mapping.EmbeddedMapper.readCollection(EmbeddedMapper.java:142) [Test-1.5-SNAPSHOT-shaded.jar:?]
    at org.mongodb.morphia.mapping.EmbeddedMapper.fromDBObject(EmbeddedMapper.java:45) [Test-1.5-SNAPSHOT-shaded.jar:?]
    at org.mongodb.morphia.mapping.Mapper.readMappedField(Mapper.java:772) [Test-1.5-SNAPSHOT-shaded.jar:?]
    at org.mongodb.morphia.mapping.Mapper.fromDb(Mapper.java:230) [Test-1.5-SNAPSHOT-shaded.jar:?]
    at org.mongodb.morphia.mapping.Mapper.fromDBObject(Mapper.java:191) [Test-1.5-SNAPSHOT-shaded.jar:?]
    at org.mongodb.morphia.query.MorphiaIterator.convertItem(MorphiaIterator.java:134) [Test-1.5-SNAPSHOT-shaded.jar:?]
    at org.mongodb.morphia.query.MorphiaIterator.processItem(MorphiaIterator.java:146) [Test-1.5-SNAPSHOT-shaded.jar:?]
    at org.mongodb.morphia.query.MorphiaIterator.next(MorphiaIterator.java:117) [Test-1.5-SNAPSHOT-shaded.jar:?]
    at org.mongodb.morphia.query.QueryImpl.get(QueryImpl.java:220) [Test-1.5-SNAPSHOT-shaded.jar:?]
    at org.mongodb.morphia.dao.BasicDAO.findOne(BasicDAO.java:180) [Test-1.5-SNAPSHOT-shaded.jar:?]
    at me.mattrick.test.storage.UserRepository.getUserFromPlayer(UserRepository.java:22) [Test-1.5-SNAPSHOT-shaded.jar:?]
    at me.mattrick.test.event.JoinEvent.onJoin(JoinEvent.java:37) [Test-1.5-SNAPSHOT-shaded.jar:?]
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[?:1.8.0_101]
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[?:1.8.0_101]
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[?:1.8.0_101]
    at java.lang.reflect.Method.invoke(Method.java:498) ~[?:1.8.0_101]
    at org.bukkit.plugin.java.JavaPluginLoader$1.execute(JavaPluginLoader.java:306) [spigot-1.8.8.jar:git-Spigot-e4d4710-e1ebe52]
    at org.bukkit.plugin.RegisteredListener.callEvent(RegisteredListener.java:62) [spigot-1.8.8.jar:git-Spigot-e4d4710-e1ebe52]
    at org.bukkit.plugin.SimplePluginManager.fireEvent(SimplePluginManager.java:502) [spigot-1.8.8.jar:git-Spigot-e4d4710-e1ebe52]
    at org.bukkit.plugin.SimplePluginManager.callEvent(SimplePluginManager.java:487) [spigot-1.8.8.jar:git-Spigot-e4d4710-e1ebe52]
    at net.minecraft.server.v1_8_R3.PlayerList.onPlayerJoin(PlayerList.java:298) [spigot-1.8.8.jar:git-Spigot-e4d4710-e1ebe52]
    at net.minecraft.server.v1_8_R3.PlayerList.a(PlayerList.java:157) [spigot-1.8.8.jar:git-Spigot-e4d4710-e1ebe52]
    at net.minecraft.server.v1_8_R3.LoginListener.b(LoginListener.java:144) [spigot-1.8.8.jar:git-Spigot-e4d4710-e1ebe52]
    at net.minecraft.server.v1_8_R3.LoginListener.c(LoginListener.java:54) [spigot-1.8.8.jar:git-Spigot-e4d4710-e1ebe52]
    at net.minecraft.server.v1_8_R3.NetworkManager.a(NetworkManager.java:231) [spigot-1.8.8.jar:git-Spigot-e4d4710-e1ebe52]
    at net.minecraft.server.v1_8_R3.ServerConnection.c(ServerConnection.java:148) [spigot-1.8.8.jar:git-Spigot-e4d4710-e1ebe52]
    at net.minecraft.server.v1_8_R3.MinecraftServer.B(MinecraftServer.java:814) [spigot-1.8.8.jar:git-Spigot-e4d4710-e1ebe52]
    at net.minecraft.server.v1_8_R3.DedicatedServer.B(DedicatedServer.java:374) [spigot-1.8.8.jar:git-Spigot-e4d4710-e1ebe52]
    at net.minecraft.server.v1_8_R3.MinecraftServer.A(MinecraftServer.java:654) [spigot-1.8.8.jar:git-Spigot-e4d4710-e1ebe52]
    at net.minecraft.server.v1_8_R3.MinecraftServer.run(MinecraftServer.java:557) [spigot-1.8.8.jar:git-Spigot-e4d4710-e1ebe52]
    at java.lang.Thread.run(Thread.java:745) [?:1.8.0_101]
[22:17:13 WARN]: Class not found defined in dbObj: 
java.lang.ClassNotFoundException: me.mattrick.test.storage.TestStat
    at java.net.URLClassLoader.findClass(URLClassLoader.java:381) ~[?:1.8.0_101]
    at java.lang.ClassLoader.loadClass(ClassLoader.java:424) ~[?:1.8.0_101]
    at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:331) ~[?:1.8.0_101]
    at java.lang.ClassLoader.loadClass(ClassLoader.java:357) ~[?:1.8.0_101]
    at java.lang.Class.forName0(Native Method) ~[?:1.8.0_101]
    at java.lang.Class.forName(Class.java:348) ~[?:1.8.0_101]
    at org.mongodb.morphia.mapping.DefaultCreator.getClass(DefaultCreator.java:175) [Test-1.5-SNAPSHOT-shaded.jar:?]
    at org.mongodb.morphia.mapping.DefaultCreator.createInstance(DefaultCreator.java:87) [Test-1.5-SNAPSHOT-shaded.jar:?]
    at org.mongodb.morphia.mapping.DefaultCreator.createInstance(DefaultCreator.java:102) [Test-1.5-SNAPSHOT-shaded.jar:?]
    at org.mongodb.morphia.mapping.EmbeddedMapper.readMapOrCollectionOrEntity(EmbeddedMapper.java:205) [Test-1.5-SNAPSHOT-shaded.jar:?]
    at org.mongodb.morphia.mapping.EmbeddedMapper.readCollection(EmbeddedMapper.java:142) [Test-1.5-SNAPSHOT-shaded.jar:?]
    at org.mongodb.morphia.mapping.EmbeddedMapper.fromDBObject(EmbeddedMapper.java:45) [Test-1.5-SNAPSHOT-shaded.jar:?]
    at org.mongodb.morphia.mapping.Mapper.readMappedField(Mapper.java:772) [Test-1.5-SNAPSHOT-shaded.jar:?]
    at org.mongodb.morphia.mapping.Mapper.fromDb(Mapper.java:230) [Test-1.5-SNAPSHOT-shaded.jar:?]
    at org.mongodb.morphia.mapping.Mapper.fromDBObject(Mapper.java:191) [Test-1.5-SNAPSHOT-shaded.jar:?]
    at org.mongodb.morphia.query.MorphiaIterator.convertItem(MorphiaIterator.java:134) [Test-1.5-SNAPSHOT-shaded.jar:?]
    at org.mongodb.morphia.query.MorphiaIterator.processItem(MorphiaIterator.java:146) [Test-1.5-SNAPSHOT-shaded.jar:?]
    at org.mongodb.morphia.query.MorphiaIterator.next(MorphiaIterator.java:117) [Test-1.5-SNAPSHOT-shaded.jar:?]
    at org.mongodb.morphia.query.QueryImpl.get(QueryImpl.java:220) [Test-1.5-SNAPSHOT-shaded.jar:?]
    at org.mongodb.morphia.dao.BasicDAO.findOne(BasicDAO.java:180) [Test-1.5-SNAPSHOT-shaded.jar:?]
    at me.mattrick.test.storage.UserRepository.getUserFromPlayer(UserRepository.java:22) [Test-1.5-SNAPSHOT-shaded.jar:?]
    at me.mattrick.test.event.JoinEvent.onJoin(JoinEvent.java:37) [Test-1.5-SNAPSHOT-shaded.jar:?]
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[?:1.8.0_101]
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[?:1.8.0_101]
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[?:1.8.0_101]
    at java.lang.reflect.Method.invoke(Method.java:498) ~[?:1.8.0_101]
    at org.bukkit.plugin.java.JavaPluginLoader$1.execute(JavaPluginLoader.java:306) [spigot-1.8.8.jar:git-Spigot-e4d4710-e1ebe52]
    at org.bukkit.plugin.RegisteredListener.callEvent(RegisteredListener.java:62) [spigot-1.8.8.jar:git-Spigot-e4d4710-e1ebe52]
    at org.bukkit.plugin.SimplePluginManager.fireEvent(SimplePluginManager.java:502) [spigot-1.8.8.jar:git-Spigot-e4d4710-e1ebe52]
    at org.bukkit.plugin.SimplePluginManager.callEvent(SimplePluginManager.java:487) [spigot-1.8.8.jar:git-Spigot-e4d4710-e1ebe52]
    at net.minecraft.server.v1_8_R3.PlayerList.onPlayerJoin(PlayerList.java:298) [spigot-1.8.8.jar:git-Spigot-e4d4710-e1ebe52]
    at net.minecraft.server.v1_8_R3.PlayerList.a(PlayerList.java:157) [spigot-1.8.8.jar:git-Spigot-e4d4710-e1ebe52]
    at net.minecraft.server.v1_8_R3.LoginListener.b(LoginListener.java:144) [spigot-1.8.8.jar:git-Spigot-e4d4710-e1ebe52]
    at net.minecraft.server.v1_8_R3.LoginListener.c(LoginListener.java:54) [spigot-1.8.8.jar:git-Spigot-e4d4710-e1ebe52]
    at net.minecraft.server.v1_8_R3.NetworkManager.a(NetworkManager.java:231) [spigot-1.8.8.jar:git-Spigot-e4d4710-e1ebe52]
    at net.minecraft.server.v1_8_R3.ServerConnection.c(ServerConnection.java:148) [spigot-1.8.8.jar:git-Spigot-e4d4710-e1ebe52]
    at net.minecraft.server.v1_8_R3.MinecraftServer.B(MinecraftServer.java:814) [spigot-1.8.8.jar:git-Spigot-e4d4710-e1ebe52]
    at net.minecraft.server.v1_8_R3.DedicatedServer.B(DedicatedServer.java:374) [spigot-1.8.8.jar:git-Spigot-e4d4710-e1ebe52]
    at net.minecraft.server.v1_8_R3.MinecraftServer.A(MinecraftServer.java:654) [spigot-1.8.8.jar:git-Spigot-e4d4710-e1ebe52]
    at net.minecraft.server.v1_8_R3.MinecraftServer.run(MinecraftServer.java:557) [spigot-1.8.8.jar:git-Spigot-e4d4710-e1ebe52]
    at java.lang.Thread.run(Thread.java:745) [?:1.8.0_101]

As you can see, I am running it inside a Spigot server (which is essentially a Minecraft server with a proper API implementation). I'm not sure if this is terribly relevant, but the Spigot server loads plugins in a similar way that Morphia would, so I think it may be possible that this is causing this issue, since there's been previous documented instances of Morphia conflicting with other libraries that use class loaders.

Adding "noClassnameStored = true" to the @Entity annotation seems to prevent this error, however I am storing a list of custom objects inside the database, which also causes this error.

The models I am using can be seen below:

Stat.java:

package me.mattrick.test.storage;

public class Stat {
}

TestStat.java:

package me.mattrick.test.storage;

import lombok.Getter;
import lombok.Setter;

public class TestStat extends Stat {

    @Getter @Setter
    private int test = 100;

}

User.java:

package me.mattrick.test.storage;

import lombok.Getter;
import lombok.Setter;
import me.mattrick.test.Test;
import me.mattrick.test.api.storage.mongo.MongoEntity;
import me.mattrick.test.cosmetics.particles.EnumParticleEffect;
import me.mattrick.test.player.PlayerRank;
import org.bukkit.Bukkit;
import org.bukkit.entity.Player;
import org.mongodb.morphia.annotations.Entity;

import java.time.LocalDateTime;
import java.util.ArrayList;
import java.util.List;
import java.util.UUID;

@Entity(value = "users", noClassnameStored = true)
public class User extends MongoEntity {

    @Getter @Setter
    private UUID uuid;

    @Getter @Setter
    private PlayerRank rank = PlayerRank.DEFAULT;

    @Getter @Setter
    private EnumParticleEffect effect = EnumParticleEffect.NONE;

    @Getter @Setter
    private int money = 0;

    @Getter @Setter
    private int level = 0;

    @Getter @Setter
    private long experience = 0;

    @Getter @Setter
    private LocalDateTime firstJoined;

    @Getter @Setter
    private LocalDateTime lastPlayed;

    @Getter @Setter
    private List<Stat> stats = new ArrayList<>();

    public Player getPlayer() {
        return Bukkit.getPlayer(uuid);
    }

    public void save() {
        Test.getInstance().getMongoBridge().repositoryBy(User.class).save(this);
    }

    public <T extends Stat> T getStat(Class<T> statClass) {
        for (Stat stat : stats) {
            if(stat.getClass() == statClass) {
                return statClass.cast(stat);
            }
        }
        return null;
    }

    public void addStat(Stat stat) {
        stats.add(stat);
    }

}

MongoEntity.java:

package me.mattrick.test.api.storage.mongo;

import lombok.Getter;
import lombok.Setter;
import org.bson.types.ObjectId;
import org.mongodb.morphia.annotations.Id;

public class MongoEntity {

    @Id
    @Getter @Setter
    private ObjectId id;

}

It should be noted that the User class saves and loads fine as a result of the "noClassnameStored = true" parameter set on the @Entity annotation, but the Stat class does not, since this is not feasible for this.

Would anyone happen to know the solution to this? Its a rather odd error, and I'm not too experienced with Morphia. Thank you for you assistance and apologies for such a long post.

Answer 1

For anyone who's coming across this issue (like I did) in 2020 and uses PaperSpigot, here's what I managed to do after resorting to Morphia's documentation. I am using Morphia v1.6.0 and PaperSpigot 1.16.2.

morphia.getMapper().setOptions(
    MapperOptions.legacy().classLoader(<MainClass>.class.getClassLoader())
        .build()
);

Here's an explanation:

1. The accepted answer shows that you can use .setObjectFactory to achieve this change. In my IDE (IntelliJ), it wasn't only marked as deprecated, but using that along with the DefaultCreator wasn't doing the job. I don't think it's accepted practice in the new version(s) of Morphia? Anyways, I ended up using the setOptions method using the legacy builder for setting MapperOptions. This method wasn't deprecated either.
2. In the accepted answer, it shows the usage of JavaPlugin.getClassLoader(). That method is protected. Therefore you cannot access it directly. However, if you use your plugin's main class, for instance, you can access the getClassLoader() method with no issues. You're not going to want to directly access these methods unless you're trying to do some weird/hacky stuff.

Answer 2

I've managed to figure it out. You need to override Morphia's ClassLoader with your plugin's own. In case anyone using Spigot or Bukkit are looking for the answer:

morphia.getMapper().getOptions().setObjectFactory(new DefaultCreator() {
    @Override
    protected ClassLoader getClassLoaderForClass() {
        return JavaPlugin.getClassLoader();
    }
});

Answer 3

That error usually stems from a broken classpath. It would appear that you spigot server isn't including the jar with your entities on the classpath when it starts up.