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Freemarker Xml Extension (FMX) -

FMX stands for Freemarker XML extension. Freemarker is a famous templating engine which has been used in various products such as Magnolia CMS , CoreMedia CMS or various other applications/tools. Freemarker has an easy to use and most of all a quite intutitive syntax and it provides easy mechanisms for extensions. In contrast to languages such as StringTemplates or Handlebars it’s not logic less. Some people consider this to be a disadvantage as I myself did in my early days of using templating languages. Nevertheless the term logic less is used loosely in my opinion because in general you always end up in writing helper functions to cover the logic so the problem itself has only been moved. But why is the term “logic less” attractive? The answer herefore is quite clear as the support for logic means that the templates might get overloaded with control statements, data manipulation etc and thus the code that’s supposed to be rendered becomes more or less obfuscated. This makes it harder for these templates to be maintained as they are ugly to read (as usual it depends on the skills of the template author to restrict the used logic to a minimum).

That’s where FMX comes into play. FMX is an XML based representation of Freemarker templates. This introduces the following advantages:


Using the FMX extension requires the following dependency:

Maven Gradle Scala
compile 'com.kasisoft:com.kasisoft.libs.fmx:0.7'
libraryDependencies += "com.kasisoft" % "com.kasisoft.libs.fmx" % "0.7"

The following example demonstrates the usage in case you are using Freemarker directly. It essentially boils down to register the FmxTemplateLoader which actually does the whole work. Apart from the marked lines (NOTE) the other code is pretty standard.

ClassTemplateLoader baseLoader = new ClassTemplateLoader(MyClass.class, "/");

// !!! NOTE: This is the Freemarker TemplateLoader which does the work
FmxTemplateLoader   fmxLoader  = new FmxTemplateLoader(baseLoader);

// choose the version according to your needs !
Configuration       config     = new Configuration(Configuration.VERSION_2_3_23);

// !!! NOTE: Here comes the integration of the FmxTemplateLoader

Template      template = config.getTemplate("dodo.fmx", Locale.ENGLISH);
StringWriter  writer   = new StringWriter();
TemplateModel model    = ... // a bean or a hashmap depending on your needs
template.process(model, writer);
System.out.println("generated: " + writer.toString());


The usage is essentially the same as for ordinary Freemarker templates. The only difference is the .fmx suffix. If you attempt to load a normal .ftl template the loading process is delegated to the parental template loader instance, so the difference is not even recognizable from a developers point of view.

Requirements for fmx templates

FMX Constructs

Technical overview

Relationship between the FmxTemplateLoader and FmxTranslator
Relationship between the FmxTemplateLoader and FmxTranslator

The logic is quite simple. The FmxTemplateLoader uses the FmxTranslator to perform the conversions from FMX to FTL. The FmxTranslator itself just invokes a SAX Parser with the DefaultHandler implementation TranslationContext. The TranslationContext is writing the necessary Freemarker code depending on the callback invocation generated by the actual FMX template.

Performance impact

As the FMX functionality is located within the TemplateLoader it only adds a minor time delay when a template is actually being loaded. After that it’s sitting within the Freemarker cache. Since the parsing happens using a SAX parser and the rendering happens to a StringBuilder the conversion process is quite fast. There is a obviously additional time and member required to render a template but I could make out a signifikant difference while profiling (nothing real distinguishable from normal fluctuations). So it’s obvious that the use of FMX has negligible costs (regarding speed and memory).