jasperreport生成pdf_jasperreport 导出excel_jasperreport json(28)

in the document every time the value of the group expression changes during the iteration through the

data source.

Group Footer

Every time a report group changes, the engine adds the corresponding group footer section before

starting the new group or when the report ends.

Check the provided samples like jasper, datasource or query, to see how report groups can be used.

The JasperReports Ultimate Guide

Page 43

7 Scriptlets

All the data displayed on a report comes from the report parameters and from the report fields. This

data can be processed using the report variables and their expressions.

There are specific moments in time when variable processing occurs. Some variables are initialized

according to their reset type when the report starts, or when a page or column break

is encountered, or

when a group changes. Furthermore, variables are evaluated every time new data is fetched from the

data source (for every row).

But only variable expressions cannot always implement complex functionality. This is where

scriptlets intervene. Scriptlets are sequences of Java code that are executed every time a report event

occurs. Through scriptlets, users have the possibility to affect the values stored by the report variables.

Since scriptlets work mainly with report variables, is important to h

have full control over the exact

moment the scriptlet is executed.

JasperReports allows the execution of custom Java code BEFORE or AFTER it initializes the report

variables according to their reset type: Report, Page, Column or Group.

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