package org.apache.xml.serialize does not exist error

@keerthi0555 ,

You might be getting this error because "xercesImpl" jar/library is not available OOTB in AEM bundles.

In that case, you need to embed this dependency as part of your core module as external dependency.

<plugin>
   <groupId>org.apache.felix</groupId>
   <artifactId>maven-bundle-plugin</artifactId>
   <extensions>true</extensions>
   <configuration>
      <instructions>
         <!-- <Embed-Dependency> artifactId1, artifactId2;inline=true </Embed-Dependency> -->
         <Embed-Dependency>xercesImpl</Embed-Dependency>

Note: You may have to embed other dependencies which are needed for "xercesImpl" as well.

Try this out.