anchor.diff:  The Graal SDK supports substitutions of classes in the native image. An example of how one could replace the `XmlConfig/XmlData` classes with versions that have no JAXB annotation dependencies is shown in these example classes:
   
   .Substitution of XmlConfig/XmlData Classes Example
  -[source,bash]
  +[source,java]
   ----
   package io.quarkus.extest.runtime.graal;
  -
   import java.util.Date;
  -
   import com.oracle.svm.core.annotate.Substitute;
   import com.oracle.svm.core.annotate.TargetClass;
  -
   import io.quarkus.extest.runtime.config.XmlData;
  +
   @TargetClass(XmlConfig.class)
   @Substitute
  -final public class Target_XmlConfig {
  +public final class Target_XmlConfig {
  +
       @Substitute
       private String address;
       @Substitute
  
positive.code:                 ", date='" + date + '\'' +
                  '}';
      }
  
  }
  ----
  
negative.code: ./mvnw clean install -Dquarkus.debug.generated-classes-dir=./target/app-generated-classes
  ----
  
  ==== Multi-module Maven Projects and the Development Mode
  
  It's not uncommon to develop an extension in a multi-module Maven project that also contains an "example" module.
  However, if you want to run the example in the development mode then the `-DnoDeps` system property must be used in order to exclude the local project dependencies.
  Otherwise, Quarkus attempts to monitor the extension classes and this may result in weird class loading issues.
  
  [source,shell]
  ----
  ./mvnw compile quarkus:dev -DnoDeps
  ----
  
  === Sample Test Extension
  We have an extension that is used to test for regressions in the extension processing. It is located in {quarkus-tree-url}/core/test-extension directory. In this section we touch on some of the tasks an extension
  