Settings

Settings are named values that influence the behavior of FreeMarker. Examples of settings are: locale, number_format, default_encoding, template_exception_handler. The full list of settings can be found in the Java API documentation of Configuration.setSetting(...).

The settings coming from the Configuration can be overridden in a Template instance. For example, if you set the locale setting to "en_US" 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, the setting values in the Configuration serve as defaults that can be overridden in a per template manner. The value coming from the 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 ongoing processing.

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(Configuration.VERSION_2_3_25);
    myCfg.setTemplateExceptionHandler(TemplateExceptionHandler.RETHROW_HANDLER);
    myCfg.setDefaultEncoding("UTF-8");
    DefaultObjectWrapperBuilder owb = new DefaultObjectWrapperBuilder(Configuration.VERSION_2_3_25);
    owb.setForceLegacyNonListCollections(false);
    owb.setDefaultDateType(TemplateDateModel.DATETIME);
    myCfg.setObjectWrapper(owb.build());

    You do this 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 frameworks you have to specify the settings in some kind of framework-specific configuration file that require specifying settings as String name-value pairs (like in a .properties file). In that case the authors of the frameworks most probably use the Confguration.setSetting(String name, String value) method; see available setting names and the format of the values in the API documentation of setSetting. Example for Spring Framework:

    <bean id="freemarkerConfig"
        class="org.springframework.web.servlet.view.freemarker.FreeMarkerConfigurer">
      <property name="freemarkerSettings">
        <props>
          <prop key="incompatible_improvements">2.3.25</prop>
          <prop key="template_exception_handler">rethrow</prop>
          <prop key="default_encoding">UTF-8</prop>
          <prop key="object_wrapper">
            DefaultObjectWrapper(
                    2.3.25,
                    forceLegacyNonListCollections = false,
                    defaultDateType = freemarker.template.TemplateDateModel.DATETIME)
          </prop>
        </props>
      </property>
    </bean>

    Here's the same when configuring FreeMarker for Struts, which looks for a freemarker.properties in the classpath:

    incompatible_improvements=2.3.25
    template_exception_handler=rethrow
    default_encoding=UTF-8
    object_wrapper=DefaultObjectWrapper( \
            2.3.25, \
            forceLegacyNonListCollections = false, \
            defaultDateType = freemarker.template.TemplateDateModel.DATETIME)

    As demonstrated above with object_wrapper, some settings can accept quite complex values, which can be used to instantiate objects of arbitrary classes and set their properties. Still, configuring with String key-value pairs is limited compared to directly using the Java API, so in some cases you have to find a way to do this in Java.

  • Template layer: Settings on individual templates are normally set by template configurations (see them in their own chapter), which basically associate setting assignments to template name (template path) patterns. There's a deviation from this approach with the locale setting, because that you can also specify to Configuration.getTemplate(...) as parameter, to get the template for the requested locale (so called localized lookup).

    Warning!

    You should never set settings directly on the Template object that you get from Configuration.getTemplate(...)! Those objects should be treated as already initialized and read-only.

    When a template includes or imports another template, most of the settings (like locale, number_format, etc.) will remain those specified by the top-level template. The exceptions are the settings that affect the parsing of the template (like tag_syntax, whitespace_stripping, etc.), as these are not inherited from the top-level template, instead each template always uses its own values, no mater how it was invoked.

    Note:

    If you are going to use template layer settings, you should set the incompatible_improvements setting to 2.3.22 or higher, to avoid some confusing legacy bugs.

  • Environment layer: There are two ways of doing it:

    • With Java API: Use the setter methods of the Environment object. You may run into the API problem that myTemplate.process(...) both creates the Environment object internally and processes the template, so you have no opportunity to adjust the Environment in between. The solution is that those 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 (considered as bad style, usually): 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 and their meaning, 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.