The Total Tag

The "total" tag, which is required to be bodiless, allows simpler aggregation operations, without "group by" properties, and specifying only one aggregate value.

Attributes

  • The "total" tag supports all base tag attributes.
  • items: List Required. This is the List of items to aggregate.
  • value: String Required. This is exactly one aggregator specification string, e.g. "Avg(price)". This represents the aggregate operation to perform on the list of values.
  • parallel: int Optional. Specify a degree of parallelism directly to the jAgg library. Default: 1

The Aggregators specified in the "value" attribute may be an Aggregator, either built-in to the jAgg library, or custom built by the developer.

The "total" tag is an alternate version of the Aggregate Expression.

Example

A List of Employees is available in the beans map. There are 4 employees, but only 2 of them have a non-null manager.

<jt:total items="${employees}" value="Count(manager)"/>

...gets transformed into...

2