C.s.p.e.IncompatibleClassException: Mutation is missing

Question

I'm getting this error and I can't figure out why.
Greatful for any hint. I'm a complete n00b and could not find anything while searching.
com.sleepycat.persist.evolve.IncompatibleClassException: Mutation is missing to evolve class: org.apache.limax.Content version: 0 to class: org.apache.limax.Content version: 0 Error: Field is not present or not persistent: author
     at com.sleepycat.persist.impl.PersistCatalog.<init>(PersistCatalog.java:338)
     at com.sleepycat.persist.impl.Store.<init>(Store.java:172)
     at com.sleepycat.persist.EntityStore.<init>(EntityStore.java:148)
@Entity
public class Content {
@PrimaryKey(sequence = "ID")
private Integer ID;
private List<String> classifiedFacettClassIDs = new ArrayList<String>();
private String title;
private String summary;
@SecondaryKey(relate = Relationship.ONE_TO_ONE)
private String URL;
@SecondaryKey(relate = Relationship.MANY_TO_ONE, relatedEntity = User.class)
private String authorID;
private Date dateCreated = new Date();
public Content() {
@Entity
public class User {
@PrimaryKey
private String ID;
private List<Preference> preferences = new ArrayList<Preference>();
@Persistent
public class Preference implements Comparable<Preference> {
private Integer contentID;
private Double value;
@Entity
public class Comment {
@PrimaryKey(sequence = "ID")
private Integer ID;
@SecondaryKey(relate = Relationship.MANY_TO_ONE, relatedEntity = Content.class, onRelatedEntityDelete = DeleteAction.CASCADE)
private Integer contentID;
@SecondaryKey(relate = Relationship.MANY_TO_ONE, relatedEntity = User.class)
private String authorID;
@SecondaryKey(relate = Relationship.MANY_TO_ONE, relatedEntity = Comment.class)
private Integer inReplyToID;
private Date dateCreated;
private String textValue;
}

Answer 1

Hello Tony,
The IncompatibleClassException is thrown when you change a class and you haven't given the DPL enough information to know how to evolve the existing data for that class to the new class definition. If you are just doing development, then you probably just forgot to clear out the old data (delete the files in the environment directory) when you changed your code and tried your test again.
More specifically, this exception:
com.sleepycat.persist.evolve.IncompatibleClassException: Mutation is missing to evolve class: org.apache.limax.Content version: 0 to class: org.apache.limax.Content version: 0 Error: Field is not present or not persistent: author
Means that the "author" field was previously present in the Content class and is no longer present. If you rename or delete a field, you have to tell the DPL what to do with the author field data in the old stored records. It looks like you renamed it to authorID.
If you have a deployed application and you wish to rename a field, you can configure a Renamer mutation.
For more information on class evolution see:
http://www.oracle.com/technology/documentation/berkeley-db/je/java/com/sleepycat/persist/evolve/package-summary.html#package_description
Mark