CTL is a proprietary scripting language oriented on data processing in transformation components of CloverETL.
It is designed to allow simple and clear notation of how data is processed and yet provide sufficient means for its manipulation.
Language syntax resembles Java with some constructs common in scripting languages. Although scripting language itself, CTL code organization into function resembles structure of Java classes with clearly defined methods designating code entry points.
CTL is a high level language in both abstraction of processed data as well as its execution environment. The language shields programmer from the complexity of overall data transformation, while refocusing him to develop a single transformation step as a set of operations applicable onto all processed data records.
Closely integrated with CloverETL environment, the language also benefits the programmer with uniform access to elements of data transformation located outside the executing component, operations with values of types permissible for record fields, and a rich set of validation and manipulation functions.
During transformation execution, each component running CTL code uses separate interpreter instance; thus preventing possible collisions in heavily parallel multi-threaded execution environment of CloverETL.
Example 58.1. Example of CTL2 code
//#CTL2
function integer transform() {
if ( $in.0.hasDetail ) {
$out.0.name = $in.0.name;
$out.0.email = $in.0.email;
return 0;
}
$out.1.name = $in.0.name;
return 1;
}Easy scripting language
Clover transformation language (CTL) is a very simple scripting language that can serve for writing transformations in a great number of CloverETL components.
Although Java can be used in all of these components, working with CTL is much easier.
Typed language
CTL2 is strongly typed. Each variable has its data type. The declarations of container types contain the data types as well.
Arbitrary Order of Code Parts
Declare your variable where you need them.
CTL2 allows to declare variables and functions in any place of the code. Only one condition must be fulfilled - each variable and function must be declared before it is used.
CTL2 also allows to define mapping in any place of the transformation and be followed by other code.
Parts of CTL2 code may be interspersed almost arbitrarily.
Almost as fast as Java
Transformations written in CTL are almost as fast as those written in Java.
Source code of CTL2 can even be compiled into Java class.
Compiled mode
CTL2 code can be transformed into pure Java which greatly increases speed of the transformation. This is called "compiled mode" and CloverETL can do it for you transparently each time you run a graph with CTL2 code in it. The transformation into compiled form is done internally so you do not need to be Java programmer to use it.
Each time you use a component with CTL2 transform and explicitly set it to work in compiled mode, CloverETL produces an in-memory Java code from your CTL and runs the Java natively - giving you a great speed increase.
Used in many CloverETL components
CTL can be used in all of the components whose overview is provided in Transformations Overview, except in JMSReader and JMSWriter.
Used even without knowledge of Java
Even without any knowledge of Java, the user can write the code in CTL.
Access to Graph Elements (Lookups, Sequences, ...)
A strict type checking is further extended to validation of lookup tables and sequences access. For lookup tables, the actual arguments of lookup operation are validated against lookup table keys, while using the record returned by table in further type checked.
Sequences support three possible return types explicitly set by the user: integer, long and string.
The current version of CTL is CTL2. It is available since version 3.0 of CloverETL. The usage of older version of CTL (CTL1) is deprecated since version 4.0.0.M2 of CloverETL. You are strongly advised to use CTL2.
In the following chapters and sections we provide a thorough description of current version of CTL.