Before you begin
If you want to use continuous query, then you must enable IBM® eXtremeIO, which is a transport
mechanism, that is used to communicate between container servers and
clients. For more information about enabling eXtremeIO, see
Configuring IBM eXtremeIO (XIO).
About this task
When you develop client applications that interact with the
data grid, you might require queries that retrieve automatic, real-time
results when entries that match the filtering criteria are inserted,
updated or deleted. For example, you develop a stock quote application
that requires frequent updates. These updates reflect changes that
occur in the stock market. Therefore, it is critical that your application
is notified of changes instantly, so that you can supply accurate
and timely results. Continuous query has a low-memory footprint that
can proactively notify clients as changes in the data grid occur.
Use the following procedure to program your client applications to
use continuous query.
Restriction: Queries that specify a value attribute path of null are not supported if the value object is not a primitive Java type, such as a string or integer.
When null is specified, the query filter is used
to query the entire value object.
What to do next
See
API documentation: Package com.ibm.websphere.objectgrid.continuousquery for more information about the continuous query API.