Settings are named values that influence the behavior of FreeMarker. Examples of settings are: locale, number_format
Settings stored in Configuration instance can be overridden in a Template instance. For example you set "en_US" for the locale setting in the configuration, then the locale in all templates that use this configuration will be "en_US", except in templates where the locale was explicitly specified differently (see localization). Thus, values in a Configuration serve as defaults that can be overridden in a per template manner. The value comes from Configuration instance or Template instance can be further overridden for a single Template.process call. For each such call a freemarker.core.Environment object is created internally that holds the runtime environment of the template processing, including the setting values that were overridden on that level. The values stored there can even be changed during the template processing, so a template can set settings itself, like switching locale at the middle of the output.
This can be imagined as 3 layers (Configuration, Template, Environment) of settings, where the topmost layer that contains the value for a certain setting provides the effective value of that setting. For example (settings A to F are just imaginary settings for this example):
|Setting A||Setting B||Setting C||Setting D||Setting E||Setting F|
|Layer 3: Environment||1||-||-||1||-||-|
|Layer 2: Template||2||2||-||-||2||-|
|Layer 1: Configuration||3||3||3||3||-||-|
The effective value of settings will be: A = 1, B = 2, C = 3, D = 1, E = 2. The F setting is probably null, or it throws exception when you try to get it.
Let's see exactly how to set settings:
Configuration layer: In principle you set the settings with the setter methods of the Configuration object, fore example:
Configuration myCfg = new Configuration(); myCfg.setLocale(java.util.Locale.ITALY); myCfg.setNumberFormat("0.####");
You do it before you start to actually use the Configuration object (typically, when you initialize the application); you should treat the object as read-only after that.
In practice, in most Web application frameworks you have to specify the setting in a framework-specific configuration file that require specifying setting as String name-value pairs (like in a .properties file). In that case the authors of the frameworks most probably use the setSetting(String name, String value) method of Configuration; see available setting names and the format of the values in the API doc of setSetting. Example for Spring Framework:
<bean id="freemarkerConfig" class="org.springframework.web.servlet.view.freemarker.FreeMarkerConfigurer"> <property name="freemarkerSettings"> <props> <prop key="locale">it_IT</prop> <prop key="number_format">0.####</prop> </props> </property> </bean>
Note that this kind of configuring (String key-value pairs) is unfortunately limited compared to directly using the API of Configuration.
Template layer: You shouldn't set settings here, unless you manage the Template objects instead of a freemarker.cache.TemplateCache, in which case you should set the setting before the Template object is first used, and then treat the Template object as read-only.
Environment layer: There are two ways doing it:
With Java API: Use the setter methods of the Environment object. Certainly you want to do that just before the processing of the template is started, and then you run into the problem that when you call myTemplate.process(...) it creates the Environment object internally and the immediately processes the template, so you had no chance. The solution is that this two steps can be separated like this:
Environment env = myTemplate.createProcessingEnvironment(root, out); env.setLocale(java.util.Locale.ITALY); env.setNumberFormat("0.####"); env.process(); // process the template
Directly in the Template: Use the setting directive, for example:
<#setting locale="it_IT"> <#setting number_format="0.####">
There are no restriction regarding when can you change the settings in this layer.
To see the list of supported settings, please read the following parts of the FreeMarker Java API documentation:
Setter methods of freemarker.core.Configurable for the settings that are in all three layers
Setter methods of freemarker.template.Configuration for the settings that are available only in the Configuration layer
freemarker.core.Configurable.setSetting(String, String) for settings that are available in all three layers and are writable with String key-value pairs.
freemarker.template.Configuration.setSetting(String, String) for settings that are available only in the Configuration layer and are writable with String key-value pairs.