Symptoms

After upgrading Confluence from a pre-4.x version to 4.x, a stacktrace is thrown when trying to view historical page versions created prior to the upgrade.

The following appears on-screen and in the atlassian-confluence.log:

java.lang.UnsupportedOperationException: The body of this ContentEntityObject ('Example Page Name') was 'BodyType:WIKI' but was expected to be 'BodyType:XHTML'
at com.atlassian.confluence.core.ContentEntityObject.getBodyContent(ContentEntityObject.java:201)
at com.atlassian.confluence.core.ContentEntityObject.getBodyAsString(ContentEntityObject.java:238)
at net.customware.confluence.plugin.pageapproval.PageApprovalSpaceViewPageAction.execute(PageApprovalSpaceViewPageAction.java:60)

Cause

This is due to the Page Approval Plugin.

Workaround

1. Ensure that the Page Approval Plugin is up to date.
2. Re-run the XHTML migration by following the instructions here
3. If historical page versions still do not work, disable the Page Approval Plugin via the Universal Plugin Manager at Confluence Admin > Manage Add-ons, then re-run the migration again.