Computed indicators must be rendered to the application administrator. jMonit uses the Visitor pattern to expose the monitor (and its aggregators) datas.
An Aggregator MAY implement the
interface. In such case, it is reponsible to compute a Map
representation of its state and pass it to the visitor. Some
aggregators may not be visitable, and in such case are ignored.
This can be used for example to create an aggregator that stores
application state on shutdown, but has no data to report.
The Visitor pattern can be used by custom application code to
build a report on the monitoring state, by simply binding a
implementation to the adequate formatting methods. jMonit uses a
second level of abstraction via the
interface. This one is used by the RestServlet to provide
The RestServlet accepts REST style URIs. The request path is composed as :
/monitors: all monitors, but only name and tags are returned
/monitors/tag/web: all monitors tagged as "web"
/monitors/tag/web/Statistics: all monitors tagged as "web" AND supporting the "Statistics" feature. The feature datas are also returned
/monitors/tag/web/Statistics+Concurrency: all monitors tagged as "web" AND supporting both the "Statistics" and "Concurrency" features.
The data formatting depends on the request "accept" header. It
also considers the request path extension. Based on this, a
renderer instance is used. For example, request to
with accept header set to
will use the JsonRenderer. Based on this, we can render the
monitored datas in many formats, like XML, CSV, PDF...
jMonit provides a web UI built over the REST+json facility. It uses the prototype js library to parse the JSON result and render datas in a grid. Point your browser to http://myserver/myapp/jMonit/performances.html to see it in action.