jasper report table show previous page total

Question

I am using Jaspersoft® Studio 6.8.0.

I want to have a table which can show previous page total, take following table for example, assume this table has 3 pages:

                     grade
                     10
                     20
        sub total    30
                             page 1
                     grade
previous page total  30
                     40
                     50
          sub total  90
                            page 2
                     grade
previous page total  90
                     60
                     70
         sub total   130
                            page 3

that is show previous page total from 2nd page to last page.

How to achieve that? thanks!

Answer 1

One way to do it is to create a variable that holds a mutable value set as a side effect by an expression of the text that displays the total on the previous page.

E.g. something like this:

    <variable name="TotalVariable" class="java.lang.Integer" calculation="Sum" resetType="Page">
        <variableExpression>$F{Column}</variableExpression>
    </variable>
    <variable name="PreviousTotalHolder" class="java.util.concurrent.atomic.AtomicInteger" calculation="System">
        <initialValueExpression>new java.util.concurrent.atomic.AtomicInteger()</initialValueExpression>
    </variable>
    ...display the previous total in the new page
                        <textField>
                            <reportElement .../>
                            <textFieldExpression>"Previous total " + $V{PreviousTotalHolder}.get()</textFieldExpression>
                        </textField>
    ...use a dummy property in the page footer to set the total into the holder object
                        <textField>
                            <reportElement x="0" y="0" width="90" height="15" uuid="a1ab288e-ae4b-4f12-83a5-e30486bb30d5">
                                <propertyExpression name="foo">Integer.toString($V{PreviousTotalHolder}.getAndSet($V{TotalVariable}))</propertyExpression>
                            </reportElement>
                            <textFieldExpression>"Total " + $V{TotalVariable}</textFieldExpression>
                        </textField>

There might be other ways to do it depending on the exact design of you report (for instance depending on whether you have a table component or a tabular band report).