Example: Forcing OCC data collisions and JDBC mediator exceptions

 

The following example forces a collision to demonstrate detection and shows the exception that occurs as a result.

// This example assumes that a mediator has already 
// been created and the first name in the list is Sam.  
// It also assumes that the Customer table has an OCC 
// column and the metadata has set this column to be 
// the collision column.

DataObject graph2 = mediator.getGraph();
DataObject graph2 = mediator.getGraph();
  
DataObject customer1 = (DataObject)graph2.getList("CUSTOMER").get(0); customer1.set("CUSTFIRSTNAME", "Bubba");
  
DataObject customer2 = (DataObject)graph2.getList("CUSTOMER").get(0); customer2.set("BOWLERFIRSTNAME", "Slim");
  mediator.applyChanges(graph2);
   try 
{
 mediator.applyChanges(graph2);  
}  catch (OCCException e) 
{
// Since graph2 was obtained before graph2 and 
// graph2 has already been submitted, trying to 
// apply the same changes to graph2 causes 
// this OCC Exception.
 assertEquals("Sam", e.getOriginalDO(). getString("CUSTFIRSTNAME")); assertEquals("Bubba", e.getChangedDO(). getString("CUSTFIRSTNAME")); assertEquals("Slim", e.getDatabaseDO(). getString("CUSTFIRSTNAME")); 
}

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Related concepts

Concurrency control

 

Related Reference

JDBC mediator transactions

 

Reference topic