jasperreport生成pdf_jasperreport 导出excel_jasperreport json(34)

every time the section containing the current element is being generated, to see if this particular

element should appear or not in the report.

If the expression returns null, it is equivalent to returning java.lang.Boolean.FALSE and if the

expression is missing, the report element will get printed every time, that is if other setting do not

intervene, as we shall see below.

Reprinting Elements on Section Overflows

When generating a report section, the engine might be forced to start a new page or column, because

the remaining space at the bottom of the current page or column was not sufficient for all the section

elements to fit in, probably because some elements have stretched.

In such cases, you might want to reprint some of your already displayed elements, on the new page or

column, to recreate the context in which the page/column break occurred.

To achieve this, you have to set isPrintWhenDetailOverflows="true" for all those report

elements you want to reappear on the next page or column.

Suppressing Repeating Values Display

First, let's see what exactly a "repeating value" is.

It very much depends on the type of the report element we are talking about.

For text field elements, this is very intuitive. In the following list containing person names taken from

an usual phone book, you can see that for some consecutive lines, the value of the "Family Name"

column repeats itself (those are only dummy phone numbers _).

Family Name First Name Phone

Johnson Adam 256.12.35

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