A report can declare a number of variables. Variables represent named expressions that are used to store some global objects or perform various calculations. Once declared, they can be referred to in other expressions using a dedicated syntax. JasperAssistant groups these declarations under a single Variables node in the Outline View. New variables can be added by using the context menu associated to this node.
Variables can perform built-in types of calculations like: count, sum, average, lowest, highest, variance, etc.
For variables that perform calculations, a reset type can be specified. A reset type indicates the moment of report execution at which the variable is reinitialized. The default reset type is Report and it indicates that the variable is initialized only once at the beginning of the report, and that it performs the specified calculation until the end of the report is reached. Other reset types can be specified in order to perform calculations at page, column or group levels.
In its expression, a variable can reference other report variables, but only if those referenced variables were previously defined. This means that the order in which the variables are declared is important.
Variable Properties
Name
Name of the report variable as it is used to refer to the variable throughout the report.
Expression
Expression that determines the value that is used to perform calculations.
Value Class
Class of the variable values as obtained by evaluating the Variable's expression.
Initial Value Expression
Expression that determines the Variable's initial value.
Calculation
Specifies the calculation type to perform on the Variable's expression.
Nothing - No calculation is performed.
Count - The variable calculates the number of the not null values obtained as the result of Variable's expression evaluation.
Sum - The variable calculates the sum of the not null values obtained as the result of Variable's expression evaluation. This type is only valid for numerical variables.
Average - The variable calculates the average of the not null values obtained as the result of Variable's expression evaluation. This type is only valid for numerical variables.
Lowest - The variable calculates the lowest value obtained as the result of Variable's expression evaluation.
Highest - The variable calculates the highest value obtained as the result of Variable's expression evaluation.
Standard Deviation - The variable calculates the standard deviation of the not null values obtained as the result of Variable's expression evaluation. This type is valid only for numerical variables. This type is only valid for numerical variables.
Variance - The variable calculates the variance of the not null values obtained as the result of Variable's expression evaluation. This type is valid only for numerical variables. This type is only valid for numerical variables.
System - Custom calculation.
Reset Time
Indicates the moment of report execution at which the variable is reinitialized.
Report - The variable is initialized once, at the beginning of the report.
Page - The variable is initialized at the beginning of each page.
Column - The variable is initialized at the beginning of each column.
Group - The variable is initialized each time the group specified by the Reset Group property changes its value.
None - The variable is never reinitialized.
Reset Group
Name of the group at which the variable is reinitialized, when the Reset Type property is set to Group.
Incrementer Factory Class
The name of a class that implements the net.sf.jasperreports.engine.fill.JRIncrementerFactory interface to use when creating the incrementer instance for this variable. Incrementers are objects that implement the net.sf.jasperreports.engine.fill.JRIncrementer interface and handle the incremental calculation performed on the variable's current value with every iteration in the data source.