Provide a callback for customising Freemarker variables

[ohalo]

boot automatic configuration freemarker lack freemarkerVariables

[wilkinsona]

What do you mean by "freemarkerVariables"? Can you please show what you're currently having to configure that the auto-configuration should be able to configure for you?

[ohalo]

but FreeMarkerConfigurationFactory has freemarkerVariables，i need it

[wilkinsona]

Ok, so you'd like to be able to set the freemarkerVariables property on either the auto-configured FreeMarkerConfigurationFactoryBean or on the auto-configured FreeMarkerConfigurer bean, correct? Both are subclasses of FreeMarkerConfigurationFactory.

What variables do you want to be able to set? Can you please provide some specific examples? Please note that values other than maps, lists and scalar values are not well-suited to being set via application.properties.

[ohalo]

@ConfigurationProperties(prefix = "freemarker")
public class FreeMarkerProperties extends AbstractTemplateViewResolverProperties {

	public static final String DEFAULT_TEMPLATE_LOADER_PATH = "classpath:/templates/";

	public static final String DEFAULT_PREFIX = "";

	public static final String DEFAULT_SUFFIX = ".ftl";

	/**
	 * Well-known FreeMarker keys which will be passed to FreeMarker's Configuration.
	 */
	private Map<String, String> settings = new HashMap<String, String>();

        private Map<String, String> freemarkerVariables = new HashMap<String, String>();

and configuration is

#freemarker
freemarker:
  settings:
    object_wrapper: com.control.back.halo.basic.utils.FreemarkerObjectWrapper
    datetime_format: yyyy-MM-dd HH:mm:ss
    date_format: yyyy-MM-dd
    time_format: HH:mm:ss    
  freemarker-variables:
    base: http://127.0.0.1:80

[ohalo]

in FreeMarkerAutoConfiguration ,and join factory.setFreemarkerVariables(this.properties.getFreemarkerVariables());

protected static class FreeMarkerConfiguration {

      @Autowired
      protected FreeMarkerProperties properties;

      protected void applyProperties(FreeMarkerConfigurationFactory factory) {
          factory.setTemplateLoaderPaths(this.properties.getTemplateLoaderPath());
          factory.setPreferFileSystemAccess(this.properties.isPreferFileSystemAccess());
          factory.setDefaultEncoding(this.properties.getCharsetName());
          Properties settings = new Properties();
          settings.putAll(this.properties.getSettings());
          factory.setFreemarkerSettings(settings);
          factory.setFreemarkerVariables(this.properties.getFreemarkerVariables());
      }

  }

[wilkinsona]

The formatting is much better, thank you. Unfortunately, it's not really what it was looking for.

You've shown how what you're asking for could be implemented in Spring Boot and I already know how to do that. What I don't know is what values you want to set in freemarkerVariables. You've shown one example which is setting base to http://127.0.0.1:80. What other variables would you like to be able to set and what values might they have? I am asking because the values in freemarkerVariables can be anything (it's a Map<String, Object>) and application.properties or application.yml aren't a good way to set some types of Object. As I said above, it's only suited to setting maps, lists and scalar values.

If you want to configure something that's more complex, or you just want to do this without an enhancement to Spring Boot, then registering a BeanPostProcessor for the FreeMarkerConfigurer or FreeMarkerConfigurationFactoryBean may be what you need to do.

[wo8335224]

@Configuration
public class FreemarkerConfiguration extends FreeMarkerAutoConfiguration.FreeMarkerWebConfiguration {
	@Value("${ctx.static}")
	private String ctx;
	@Value("${ctx.custom}")
	private Integer custom;

	@Override
	public FreeMarkerConfigurer freeMarkerConfigurer() {
		FreeMarkerConfigurer configurer = super.freeMarkerConfigurer();

		Map<String, Object> sharedVariables = new HashMap<>();
		if (custom != null && custom == 1) {
			sharedVariables.put("sctx", ctx);
		}
		configurer.setFreemarkerVariables(sharedVariables);
		return configurer;
	}
}

workd for me

@ohalo

[bianjp]

Spring Boot 2.0 breaks the solution provided by @wo8335224, as FreeMarkerWebConfiguration is replaced by FreeMarkerServletWebConfiguration, which is unfortunately package-private and thus cannot be subclassed.

A currently working solution is to configure freemarker.template.Configuration bean:

@Configuration
public class FreemarkerConfig {
    public FreemarkerConfig(freemarker.template.Configuration configuration) throws TemplateModelException {
        configuration.setSharedVariable("name", "whatever type of value");
    }
}

Internally FreeMarkerConfigurer#setFreemarkerVariables delegates its work to freemarker.template.Configuration#setAllSharedVariables.

[satahippy]

Hey @bianjp !

Yes, you can do this, but you'll lose some auto-configuration.
So better use BeanPostProcessor.

@Component
class FreeMarkerPostProcessor : BeanPostProcessor {
    override fun postProcessBeforeInitialization(bean: Any, beanName: String): Any {
        if (bean is FreeMarkerConfigurer) {
            bean.setFreemarkerVariables(mapOf(
                    "globalVar" to "globalVarValue"
            ))
        }
        return bean
    }
}

[kaliatech]

Thanks @satahippy. Java version:

@Configuration
public class CustomFreeMarkerConfig implements BeanPostProcessor {

    Object sharedWithAllFreeMarkerTemplatesObj = new Object();

    @Override
    public Object postProcessBeforeInitialization(Object bean, String beanName)
    throws BeansException {
        if (bean instanceof FreeMarkerConfigurer) {
            FreeMarkerConfigurer configurer = (FreeMarkerConfigurer) bean;
            Map<String, Object> sharedVariables = new HashMap<>();
            sharedVariables.put("globalVar", sharedWithAllFreeMarkerTemplatesObj);
            configurer.setFreemarkerVariables(sharedVariables);
        }
        return bean;
    }
}

[edit: my original comment confused Before/After Initialization)

I feel like there should be some easier, built-in way, of doing this, but I haven't found it yet. Related question on StackOverflow: https://stackoverflow.com/questions/52730368/how-to-make-globally-shared-objects-available-to-freemarker-templates-in-spring

[mauromol]

+1 for this. Today I encountered the same need.

[wilkinsona]

I don't think this needs to be blocked on the Framework issue. While allowing the variables to be amended could be useful, being able to set them (overwriting anything already set) would still be a step forwards. As and when there's a Framework API that allows the variables to be amended, that would be an additional benefit of a customizer callback in Boot.