_What is a template model

Template model is a Java object that contains template logic. We recommend that you put templating logic in the model rather than trying to do too much in a template script. A template renderer executes the model before it calls the template script. The model can retrieve data, perform a calculation or do anything the template needs. The result of the model's execute() method is passed to the template script with an actionResult object. The model can also act as a bean for getting or setting POST or GET parameters if the class provides the corresponding getter and setter functions.

Usage in templates

In Freemarker you can access any public function of the associated model class with the  model object. Eg:

• Model class method: public String getName()
  
  • Freemarker, full annotation: ${model.getName()}
  • Freemarker, bean annotation: ${model.name}


• Model class method: public boolean isArchived()
  
  • Freemarker, full annotation: ${model.isArchived()}
  • Freemarker, bean annotation: [#if model.archived!false] ... [/#if]


• Model class method: public String getAddress(String user)
  
  • Freemarker, full annotation: ${model.getAddress("John Smith")}
  • Note that only the full annotation works for functions that require one or more parameters.

TODO: JSP example

Model constructor

The following Java objects are always passed to a model class (TODO: from where, why):

• The current node in JCR
• The corresponding template definition class
• The parent model of the last render cycle

It is also recommended to make use of Java Generics (TODO: Link yes or no? Different link?) to ensure type safety. This avoids run time errors in case the type is being cast wrong, since it would already throw an error at compile time and could be fixed pre-production. Furthermore wildcards ( <?> ) and upper bounds for wildcards ( <? extends Number> ) can be used.

public class MyCustomModel<RD extends ConfiguredTemplateDefinition> extends RenderingModelImpl<ConfiguredTemplateDefinition> {

    public MyCustomModel(Node content, ConfiguredTemplateDefinition definition, RenderingModel<?> parent) {
        super(content, definition, parent);
    } 

}

Advantages

There are many advantages of using a model class. For example, the business logic can be exchanged while the script output remains the same. The same model class can also be reused for different templates so the code does not need to be duplicated. Since there is a clean separation between logic and output, these two can be developed independently by different developers (java vs. frontend developer). Another advantage, that is not neglectable, is the protection of your code. While it is possible to change the output of templates with the inplace templating module, you cannot change the business logic without restart of the server and without access to the source code. This applies to model classes programmed in Java, you can change the code in a running instance if you are using Groovy model classes however.