iReport Ultimate Guide - Docs.nimsoft.com

iReport Ultimate Guide
Groovy is a full language for the Java 2 Platform. Inside the Groovy language you can use all classes and JARs that are
available for Java. Table 3-4 compares some typical JasperReports expressions written in Java and Groovy.
Table 3-4
Groovy and Java code samples
Expression Java Groovy
Field $F{field_name} $F{field_name}
Sum of two
double fields
new Double($F{f1}.doubleValue() + $F{f2}.doubleValue())
$F{f1} + $F{f2}
Comparison of
numbers
new Boolean($F{f}.intValue() == 1) $F{f} == 1
Comparison of
strings
new Boolean($F{f} != null && $F{f}.equals("test"))
$F{f} == "test"
The following is a correct Groovy expression:
new JREmptyDataSource($F{num_of_void_records})
JREmptyDataSource is a class of JasperReports that creates an empty record set (meaning with the all fields set to null). You
can see how you can instance this class (a pure Java class) in Groovy without any problem. At the same time, Groovy allows
you to use a simple expression like this one:
5+5
The language automatically encapsulates the primitive value 10 (the result of that expression) in a proper object. Actually, you
can do more: you can treat this value as an object of type String and create an expression such as:
5 + 5+ ”my value”
Whether or not such an expression resolves to a rational value, it is still a legal expression and the result will be an object of
type String with the value:
10 my value
Hiding the difference between objects and primitive values, Groovy allows the comparison of different types of objects and
primitive values, such as the legal expression:
$F{Name} == “John”
This expression returns true or false, or, again:
$F{Age} > 18
Returns true if the Age object interpreted as a number is greater than
18.
“340” < 100 Always returns false.
“340”.substring(0,2) < 100
Always returns true (since the substring method call will produce the
string “34”, which is less than 100).
Groovy provides a way to greatly simplify expressions and never complains about null objects that can crash a Java expression
throwing a NullPointerException. It really does open the doors of JasperReports to people who don’t know Java.
3.8 Using JavaScript as a Language for Expressions
JavaScript is a popular scripting language with a syntax very similar to Java and Groovy. The support for JavaScript has been
requested for a long time from the community and was finally introduced in JasperReports 3.1.2, using the open source Rhino
JavaScript implementation.
JavaScript has a set of functions and object methods that in some cases differ from Java and Groovy. For example, the method
String.startsWith(...) does not exist in JavaScript. The good news is that you can still use Java objects in JavaScript. A
simple example is:
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