Discovering data sources
If your application needs to find available data sources, implement the following steps.
To discover data sources
1. Create a new Discovery event.
2. Use the Discovery event's findAvailableDataSources action.
3. Create a handler action to perform callback actions on the results of the findAvailableDataSources action.
4. In the handler action, declare a variable for a DataSource event.
The definitions for the two forms of the findAvailableDataSources action are:
action findAvailableDataSources(
float timeout,
action <string, sequence<DataSource>> callback )
and
action findAvailableDataSourcesFull(
float timeout,
dictionary<string,string> extraParams,
action <string, sequence<DataSource>> callback )
The definition of the DataSource event is:
event DataSource
{ string serviceId;
string name;
dictionary<string,string> extraParams;
}
serviceId — The service ID to talk to this
DataSource.
name — The name of the
DataSource such as ODBC, JDBC, or Sim.
extraParams — Optional parameters.
The relevant code is similar to this:
com.apama.database.Discovery adbc :=
new com.apama.database.Discovery;
adbc.findAvailableDataSources(TIME_TO_WAIT, handleAvailableServers);
action handleAvailableServers(string error,
sequence<com.apama.database.DataSource> results)
{
if error.length() != 0 {
log "Error occurred getting available data sources: " +
error at ERROR;
}
else {
if results.size() > 0 {
// Save off first service ID found.
// Assumes first data source has at least one db
if getDbServiceId() = "" {
dbServiceId := results[0].serviceId;
}
com.apama.database.DataSource ds;
log " DataSources: " at INFO;
for ds in results {
log " " + ds.name + " - " + ds.serviceId at INFO;
}
log "Finding Databases ..." at INFO;
// ... other logic ...
}
else {
log " No DataSources found" at INFO;
}
}
}