Query Classes(Q- classes not generated) for Querydsl mongodb - mongodb

Question

Failed to instantiate [org.springframework.data.mongodb.repository.support.QuerydslMongoPredicateExecutor] and hence the Q classes were not generated. Can anyone help me with what could be the issue with that?
I've added the required dependencies and the plugin as mentioned below:
<dependency>
<groupId>com.querydsl</groupId>
<artifactId>querydsl-core</artifactId>
<version>4.0.1</version>
</dependency>
<dependency>
<groupId>com.mysema.querydsl</groupId>
<artifactId>querydsl-mongodb</artifactId>
<version>3.6.6</version>
</dependency>
<dependency>
<groupId>com.mysema.querydsl</groupId>
<artifactId>querydsl-apt</artifactId>
<version>3.6.6</version>
</dependency>
<plugin>
<groupId>com.mysema.maven</groupId>
<artifactId>apt-maven-plugin</artifactId>
<executions>
<execution>
<goals>
<goal>process</goal>
</goals>
<configuration>
<outputDirectory>target/generated-sources/java</outputDirectory>
<processor>
org.springframework.data.mongodb.repository.support.MongoAnnotationProcessor
</processor>
</configuration>
</execution>
</executions>
</plugin>
Below is the error that I'm facing:
Caused by: java.lang.ClassNotFoundException: com.example.demo.QUser
at java.net.URLClassLoader.findClass(Unknown Source) ~[na:1.8.0_151]
at java.lang.ClassLoader.loadClass(Unknown Source) ~[na:1.8.0_151]
at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source) ~[na:1.8.0_151]
at java.lang.ClassLoader.loadClass(Unknown Source) ~[na:1.8.0_151]
at org.springframework.util.ClassUtils.forName(ClassUtils.java:274) ~[spring-core-5.0.6.RELEASE.jar:5.0.6.RELEASE]
at org.springframework.data.querydsl.SimpleEntityPathResolver.createPath(SimpleEntityPathResolver.java:55) ~[spring-data-commons-2.0.7.RELEASE.jar:2.0.7.RELEASE]
... 49 common frames omitted