Archive for October, 2006

122 Transaction management Here we now see the

Thursday, October 26th, 2006
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Transaction strategies 123 A code example of this is shown below: Transaction t = pm.currentTransaction(); t.setOptimistic(true); t.begin() try { String bpKey = “123″; // some valid key value BusinessPartner bp = (BusinessPartner) pm.getObjectById(bkKey); String name = bp.getName(); // bp transitions to Persistent-Nontransactional // do some work here which might take an extended time; // display the name // to the user and allow them to change it, before which // the user might go out for lunch! // retrieve the instance and update pm.refresh(bp); // bp remains Persistent-Nontransactional bp.setName(name); // bp transitions to Persistent-Dirty } catch (Exception e) { // rollback the transaction if it is still active if (t.isActive()) t.rollback(); } finally { // commit the transaction if it is still active try { // commit the transaction if it is still active if (t.isActive()) t.commit(); } catch (JDOUserException je) { // transaction rolled back advise the user that // the work they did has // not been saved and must be done again } } The instance is refreshed immediately before it is updated. The chance of concurrency assumptions being invalid is greatly reduced. However, what we have is no longer a true optimistic transaction strategy instead we have a last commit wins situation. This is equivalent to using one short-lived pessimistic transaction to read an instance, allowing the read data to be updated non-transactionally, and then committing that to the database without any regard for changes that may have occurred in the interim.
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122 Transaction management Here we now see the

Thursday, October 26th, 2006

120 Transaction management catch (JDOException je) { //

Thursday, October 26th, 2006

120 Transaction management catch (JDOException je) { //

Thursday, October 26th, 2006

118 Transaction management 7.2 Transaction interface A JDO

Thursday, October 26th, 2006

118 Transaction management 7.2 Transaction interface A JDO

Thursday, October 26th, 2006

116 Primary interfaces and classes interfaces of components,

Wednesday, October 25th, 2006

116 Primary interfaces and classes interfaces of components,

Wednesday, October 25th, 2006

114 Primary interfaces and classes interface Extent +iterator(

Wednesday, October 25th, 2006

114 Primary interfaces and classes interface Extent +iterator(

Wednesday, October 25th, 2006