Example: OCC data collisions and JDBC mediator

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 graph1 = mediator.getGraph();
DataObject graph2 = mediator.getGraph();
  
DataObject customer1 = (DataObject)graph1.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(graph1);  
} 
catch (OCCException e) 
{
// Since graph1 was obtained before graph2 and 
// graph2 has already been submitted, trying to 
// apply the same changes to graph1 causes 
// this OCC Exception.

assertEquals("Sam", e.getOriginalDO(). getString("CUSTFIRSTNAME"));
assertEquals("Bubba", e.getChangedDO(). getString("CUSTFIRSTNAME"));
assertEquals("Slim", e.getDatabaseDO(). getString("CUSTFIRSTNAME")); 
}

Related concepts
Concurrency control

Related reference
JDBC