DisplayGroups and Backtracking Too Far

Wed, 19 Dec 2007 18:27:54 -0800

I'm having trouble with DisplayGroups and a "backtracking too far" error -- without pressing the Back button on my browser, i.e. on a 'forward, progressive' link/action
I have a DisplayGroup within a WOComponentContent template. The DisplayGroup shows me a batch of entries (using a WORepetition), which are WOHyperlinks to another Component which is designed to edit the particular item. That bit works fine. Once I try to update the edited entry (submit button returning 'null'), or click on any other WO- managed link, I get a "You have backtracked too far, The application backtracking limit of XX has been exceeded". I get this without even touching the back button! No errors sent to the console. 


From what I've gleaned on Google, I sense "trouble" with  
WODisplayGroups and backtracking. But in all the examples I've found  
they involve pressing the "back" button in order to create a problem.


My efforts:


I've tried "Wonder-ising" my simple WebApp, using  
ERXBatchingDisplayGroup, but the result is the same.



I've increased the page cache limit to, say, 300 and still the result  
is the same. My database result set is only 30 or so rows. I suspect  
that the problem is nothing to do with the value of of the page cache,  
but perhaps something else is throwing an error which happens to be  
caught by the backtracking error mechanism  
(handlePageRestorationError, I think)



I've removed the WOComponentContent templates and made everything use  
straight-forward html pages, but no difference.



I've stripped all the code back to about 10 lines of java and html per  
code page, and still get the error. Am I doing something staggeringly  
stupid? Although I'm no expert I've been using WO for some years now  
and DisplayGroups before...


WO 5.3, OS X 10.5, J2SE 5

Outline code for DisplayGroup Page:

Java:
// get an editingContext
EOEditingContext ec = new EOEditingContext();
EODatabaseDataSource ds = new EODatabaseDataSource(ec,"OrderRecord");

// Initialise ERXBatchingDisplayGroup
orderListDG = new ERXBatchingDisplayGroup();
orderListDG.setNumberOfObjectsPerBatch(10);
orderListDG.setDataSource(ds);
orderListDG.setFetchesOnLoad(true);
orderListDG.fetch();

HTML:

<webobject name = "listingLoop">
  <tr>

    <td><webobject name = "editBooking"><webobject name = "orderRef" / 
></webobject></td>

  </tr>
</webobject>

listingLoop : WORepetition {
        list = orderListDG.displayedObjects;
        item = orderRecord;
}

editBooking : WOHyperlink {
        action = editBooking;
}

orderRef: WOString {
        value = orderRecord.orderID;
}

Outline code for Edit Page:

Java:

public EditOrder applyEditChanges() {   
  return null;
}

HTML:

<webobject name = "editOrderForm">
  <table>
        <tr><td>Order</td><td><webobject name = "orderRef" /></td></tr>
  </table>

  <p>Click to update any changes <webobject name = "updateEdit"></ 
webobject> </p>

</webobject>

orderRef : WOString {
        value = order.orderID;
}

updateEdit : WOSubmitButton {
        value = "Apply Changes";
        action = applyEditChanges;
}

Pressing the Submit button results in the backtracking error.

.neilmac
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