Proto class kafka.message.ExchangeMessage$Order not found in the classpath

I am trying to setup a mongo-kafka-connector against Apache Kafka 2.5.

ExchangeMessage.proto
--------------------
syntax = "proto3";
package exchange_message_def;

option java_package = "kafka.message";
option java_outer_classname = "ExchangeMessage";
option optimize_for = SPEED;

message Order {
  string oid = 1;
}

I built a jar file for this proto and placed within plugins path. But I am getting following error.

My Pom file:

<?xml version="1.0" encoding="UTF-8"?>
<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>com.data</groupId>
    <artifactId>data-exchange</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <packaging>jar</packaging>

    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <skip.tests>false</skip.tests>
    </properties>

    <dependencies>
        <!-- Unit testing -->
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.12</version>
            <scope>test</scope>
        </dependency>
        <!-- Protocol Buffers -->
        <dependency>
            <groupId>com.google.protobuf</groupId>
            <artifactId>protobuf-java</artifactId>
            <version>3.12.2</version>
        </dependency>
        <dependency>
            <groupId>com.github.os72</groupId>
            <artifactId>protoc-jar-maven-plugin</artifactId>
            <version>3.11.4</version>
        </dependency>
        <dependency>
            <groupId>io.grpc</groupId>
            <artifactId>protoc-gen-grpc-java</artifactId>
            <version>1.30.2</version>
            <type>pom</type>
        </dependency>
    </dependencies>
    <build>
        <plugins>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <configuration>
                    <source>11</source>
                    <target>11</target>
                </configuration>
            </plugin>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-jar-plugin</artifactId>
                <version>3.0.2</version>
                <configuration>
                    <finalName>${project.name}-${project.version}</finalName>
                    <archive>
                        <manifest>
                            <addClasspath>true</addClasspath>
                            <classpathPrefix>lib/</classpathPrefix>
                        </manifest>
                    </archive>
                </configuration>
            </plugin>
            <plugin>
                <artifactId>maven-assembly-plugin</artifactId>
                <version>2.5.5</version>
                <configuration>
                    <appendAssemblyId>false</appendAssemblyId>
                    <finalName>${project.name}-${project.version}</finalName>
                    <descriptors>
                        <descriptor>src/assembly/dist.xml</descriptor>
                    </descriptors>
                </configuration>
            </plugin>
            <plugin>
                <artifactId>maven-dependency-plugin</artifactId>
                <executions>
                    <execution>
                        <phase>process-sources</phase>
                        <goals>
                            <goal>copy-dependencies</goal>
                        </goals>
                        <configuration>
                            <outputDirectory>${project.build.directory}/lib</outputDirectory>
                        </configuration>
                    </execution>
                </executions>
            </plugin>
            <plugin>
                <groupId>com.github.os72</groupId>
                <artifactId>protoc-jar-maven-plugin</artifactId>
                <version>3.11.4</version>
                <executions>
                    <execution>
                        <phase>generate-sources</phase>
                        <goals>
                            <goal>run</goal>
                        </goals>
                        <configuration>
                            <protocVersion>3.12.2</protocVersion>
                            <includeDirectories>
                                <include>src/main/proto</include>
                            </includeDirectories>
                            <inputDirectories>
                                <include>src/main/proto</include>
                            </inputDirectories>
                            <outputTargets>
                                <outputTarget>
                                    <type>java</type>
                                    <addSources>main</addSources>
                                    <outputDirectory>src/main/java</outputDirectory>
                                </outputTarget>
                                <outputTarget>
                                    <type>grpc-java</type>
                                    <addSources>main</addSources>
                                    <outputDirectory>src/main/grpc</outputDirectory>
                                    <pluginArtifact>io.grpc:protoc-gen-grpc-java:1.30.2</pluginArtifact>
                                </outputTarget>
                                <outputTarget>
                                    <type>python</type>
                                    <addSources>main</addSources>
                                    <outputDirectory>src/main/python</outputDirectory>
                                </outputTarget>
                                <outputTarget>
                                    <type>js</type>
                                    <addSources>main</addSources>
                                    <outputDirectory>src/main/js</outputDirectory>
                                </outputTarget>
                            </outputTargets>
                        </configuration>
                    </execution>
                </executions>
            </plugin>
        </plugins>
    </build>
</project>

Mongo-Sink config :

{
    "name":"mongo-sink",        
    "config":{
    "name": "mongo-sink",
    "topics": "zz",
    "connector.class": "com.mongodb.kafka.connect.MongoSinkConnector",
    "tasks.max":"1",
    "key.converter": "org.apache.kafka.connect.converters.IntegerConverter",
    "value.converter": "com.blueapron.connect.protobuf.ProtobufConverter",
    "value.converter.protoClassName":"kafka.message.ExchangeMessage$Order",
    "key.converter.schemas.enable":false,
    "value.converter.schemas.enable":true,
    "connection.uri": "mongodb://user:password@localhost:27017",
    "database":"data_db",
    "collection":"zz",
    "max.num.retries":"3",
    "retries.defer.timeout":"5000",
    "key.projection.type":"none",
    "key.projection.list": "",
    "value.projection.type":"none",
    "value.projection.list": "",
    "field.renamer.mapping":"[]",
    "field.renamer.regex":"[]",
    "document.id.strategy":"com.mongodb.kafka.connect.sink.processor.id.strategy.BsonOidStrategy",
    "post.processor.chain":"com.mongodb.kafka.connect.sink.processor.DocumentIdAdder",
    "delete.on.null.values":false,
    "writemodel.strategy":"com.mongodb.kafka.connect.sink.writemodel.strategy.ReplaceOneDefaultStrategy",
    "max.batch.size":"2",
    "rate.limiting.timeout":"100",
    "rate.limiting.every.n":"100",
    "change.data.capture.handler":""
    }
}

I am getting following error:

[2020-07-10 21:51:05,694] INFO Initializing ProtobufData with args: [protoClassName=kafka.message.ExchangeMessage$Order, legacyName=legacy_name, useConnectSchemaMap=false] (com.blueapron.connect.protobuf.ProtobufConverter:45) [2020-07-10 21:51:05,695] ERROR Failed to start task mongo-sink-0 (org.apache.kafka.connect.runtime.Worker:470) org.apache.kafka.connect.errors.ConnectException: Proto class kafka.message.ExchangeMessage$Order not found in the classpath at com.blueapron.connect.protobuf.ProtobufConverter.configure(ProtobufConverter.java:48) at org.apache.kafka.connect.runtime.isolation.Plugins.newConverter(Plugins.java:293) at org.apache.kafka.connect.runtime.Worker.startTask(Worker.java:442) at org.apache.kafka.connect.runtime.distributed.DistributedHerder.startTask(DistributedHerder.java:1147) at org.apache.kafka.connect.runtime.distributed.DistributedHerder.access$1600(DistributedHerder.java:126) at org.apache.kafka.connect.runtime.distributed.DistributedHerder$12.call(DistributedHerder.java:1162) at org.apache.kafka.connect.runtime.distributed.DistributedHerder$12.call(DistributedHerder.java:1158) at java.base/java.util.concurrent.FutureTask.run(FutureTask.java:264) at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128) at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628) at java.base/java.lang.Thread.run(Thread.java:834)

blueapron / kafka-connect-protobuf-converter

Proto class kafka.message.ExchangeMessage$Order not found in the classpath #55