A report is defined by means of a type page. This is divided into different horizontal portions named bands. When the report is joined with the data generating the print, this section are printed many times according to their function (and according to the rules that the report author has set up). For instance, the page header is repeated at the beginning of every page, while the detail band i repeated for every single read record.
The type page is divided into nine predefined bands to which new groups are added. In addition, Jaspersoft Studio manages a heading band (group header) and a recapitulation band (group footer) for every group.
A band is always wide as the page width (right and left margins excluded). However, its height, even if it is established during the design phase, can vary during the print creation according to the contained elements; it can "lengthen" toward the bottom of a page in an arbitrary way. This tipicaly occurs when bands contain subreports or text fields that have to adapt to the content vertically. Generally, the height specified by the user should be considered "the minimal height" of the band. Not all bands can be stretched dynamically according to the content, in particular the column footer, page footer and last page footer bands. The sum of all band heights (except for the background) has to always be less than or equal to the page height minus the top and bottom margins.
Following there is a brief descriptions of the available bands.
- Title: this band is the first visible band. It is created only once and can be printed on a separate page. Regarding the allowed dimensions, it is not possible during designe time to exceed the report page height (top and bottom margins are included). If the title is printed on a separate page, this band height is not included in the calculation of the total sum of all band heights, which has to be less than or equal to the page height, ass as mentioned previously.
- Page Header: this band allows you to define a page header. The height specified during the design phase usually does not change during the creation process (except for the insertion of vertically resizable components, such as a text fields that contain long text and subreports). The page header appears on all printed pages in the same position defined during the design phase. Title and summary bands do not include the page header when printed on a separate page.
- Column Header: this band is printed at the beginning of each detail column. Usually, labels containing the column names of a tabular report are inserted in this band.
- Group Header: a report can contains zero or more of this bands, which permit the collection of detail records in real groups. A group header is always accompanied by a group footer (both can be indipendently visible or not). different properties are associated with a group. They deterimine its behavior from the graphic point of view. It is possible to always force a group header on a new page or in a new column and to print this band on all pages if the bands below it overflow the single page (as a page header, but at group level). It is possible to fix a minimum height required to print a group header: if it exeeds this height, the group header band will be printed on a new page (please note that a value too large for this property can create an infinite loop during printing).
- Group Footer: this band completes a group. Usually it contains fields to view subtotals or separation graphic elements, such as lines.
- Page Footer: this band appears on every page where there is a page header. Like the column footer, it is not resizable a run time.
- Last Page Footer: If you want to make the last page footer different from the other footers, it is possible to use the special last page footer band. If the band height is 0, it is completely ignored, and the layout established for the common page will also used for the last page.
- Summary: this band allows to insert fields concerning total calculations, means, or whatever you want to insert at the end of the report. In other systems, this band is oftend named report footer.
- Background: this band was introduced after insistent requests from many users who wanted to be able to create watermarks and similar effects (suche as a frame around the whole page). It can have a maximum height equal to the page height.