Java：Jasper报告上的空白页问题

Question

I have a report that has 2 sub reports in the detail band.I would like to add in a paging parameter in the column footer but when I preview my report it gives me a blank page at the end. I have set the following for my Sub Report block in the their property window.

Print Repeated Values checked

Remove Line When Blank checked

Answer 1

The response is at this link http://mattjiang.blogspot.com/2007/05/easy-way-to-remove-blank-page-generated.html

private void removeBlankPage(List<JRPrintPage> pages) {
  for (Iterator<JRPrintPage> i = pages.iterator(); i.hasNext();) {
    JRPrintPage page = i.next();
    if (page.getElements().size() == 0) {
      i.remove();
    }
  }
}

Answer 2

With the usage of this link http://mattjiang.blogspot.com/2007/05/easy-way-to-remove-blank-page-generated.html , I could navigate through the generated jasper and I found "trash elements" in my report:

int actualPage = 1;
for (Iterator<JRPrintPage> i=jasperPrint.getPages().iterator(); i.hasNext();) {
  JRPrintPage page = i.next();
  System.out.println(String.format("Page: %s, size: %s", actualPage, page.getElements().size()));
     for (Object element : page.getElements()) {
        System.out.println("Element: " + element);
        if (element instanceof JRTemplatePrintRectangle) {
            JRTemplatePrintRectangle rectangle = (JRTemplatePrintRectangle) element;
            System.out.println(String.format("Rectangle: Key: %s", rectangle.getKey()));
        }
    }
     actualPage++;
}

Answer 3

An easy way to remove blank page generated by JasperReports.

If your JasperReports report has one more sub-reports and it was generated as PDF file. In some circumstances, a blank page might be found within PDF file. Here is my solution to easily remove it.

private void removeBlankPage(List<JRPrintPage> pages) {

      for (Iterator<JRPrintPage> i=pages.iterator(); i.hasNext();) {
          JRPrintPage page = i.next();
          if (page.getElements().size() == 0)
              i.remove();
      }
  }

This method should be called before you flush your JasperPrint instance to PDF.

Followed with the sample code, it would be better to know the object hierarchy of JasperPrint.

1. A JasperPrint has one or more JRPrintPage , you can get it via getPages() method of JasperPrint . It returns a List of JRPrintPage . If you have three elements, then your printer will print 3 pages.
2. A JRPrintPage has one ore more JRPrintElement , each element might be a string of text, or a picture, or a rectangle, etc. You can change its position or content dynamically, or even add new JRPrintElement into JRPrintPage .

CREDITS : http://mattjiang.blogspot.in/2007/05/easy-way-to-remove-blank-page-generated.html