I have tried below code, it gives me exception.
Issue issue = issueEvent.getIssue();
CustomField customField = customFieldManager.getCustomFieldObject("customfield_12200");
ModifiedValue mVal = new ModifiedValue(issue.getCustomFieldValue(customField), issueEvent.getIssue().getAssignee());
customField.updateValue(null, issue, mVal, new DefaultIssueChangeHolder());
It throws exception in
public void createValue(CustomField field, Issue issue, @Nonnull T value) {
this.customFieldValuePersister.createValues(field, issue.getId(), this.getDatabaseType(), Lists.newArrayList(new Object[]{this.getDbValueFromObject(value)}));
}