Re: Deadlock issue

Thursday, April 19, 2012, 9:33:14 PM, Jacopo Cappellato wrote:

[snip]
>> I'm also surprised on the kind of wrapper used here. Most frameworks
>> should just use `new DefaultObjectWrapper()`, or `bw = new
>> BeansWrapper(); bw.setSimpleMapWrapper(true);`. However, to be honest,
>> this is messy part of FreeMarker (which wrapper to use and why), so
>> I'm not blaming the OFBiz developers. Do you access map items as
>> `someMap.get(theKey)` in templates under OFBiz?
>
> We do something like this:
>
> ${someMap.theKey}

> Do you think we should use a different object wrapper?

I'm not sure. There are two problems with the current one:

- If you look at what map keys FreeMarker sees (`<#list k as
  someMap?keys>${k} </#list>`), it mixes the actual Map keys with the
  methods of the Map class. This I already find annoying enough to
  stay away. But it's also dangerous, because if you are unlucky and
  have key like "get", then someMap.get and someMap[myDynamicKey]
  where myDynamicKey happens to be "get" will return the get method
  instead of the map item. You can think further what if you have
  a custom Map class and you add methods to it. Using
  someMap.get("theKey") is robust however, but too verbose.

- It doesn't wrap W3C DOM nodes automatically in a way so that the
  user can use FreeMarker's XML processing facility. It also doesn't
  wrap Jython or Rhino JavaScript objects nicely.

What I like to use is:

   BeansWrapper wrapper = new BeansWrapper();
   wrapper.setSimpleMapWrapper(true);

This will not expose the methods of Map-s, only the keys of it. If you
want to get a map item that has a non-string key, you don't have
someMap.get(key) anymore, but you can use someMap(key) instead. If
it's a custom Map class with custom methods that you want to call from
the template, then you are out of luck, however. And in your case
these changes wouldn't be backward-compatible.

As of supporting W3C DOM nodes, Jython and such, it's very easy to
create a custom ObjectWrapper that does that. Just look at
DefaultObjectWrapper.

As of DefaultObjectWrapper, it's burdened with backward-compatibly,
and so wraps collections on an technically awkward way, plus it
doesn't provide any hacks for the non-String key problem. I don't see
a point of using that.

Anyway, the situation with Map-s and the "advertised" object wrappers
is something that had to be hammered out for ages. Sadly nobody has
found the time/incentive for it so far...

> Thanks,
>
> Jacopo
>
>> 
>>>    protected static Configuration defaultOfbizConfig =
>>> makeConfiguration(defaultOfbizWrapper);
>>> 
>>>    public static Configuration makeConfiguration(BeansWrapper wrapper) {
>>>        Configuration newConfig = new Configuration();
>>>        newConfig.setObjectWrapper(wrapper);
>>>        newConfig.setSharedVariable("Static", wrapper.getStaticModels());
>>>        newConfig.setLocalizedLookup(false);
>>>        newConfig.setTemplateLoader(new FlexibleTemplateLoader());
>>> 
>>> newConfig.setAutoImports(UtilProperties.getProperties("freemarkerImports"));
>>>        newConfig.setTemplateExceptionHandler(new
>>> FreeMarkerWorker.OFBizTemplateExceptionHandler());
>>>        // Transforms properties file set up as key=transform name, property=transform class name
>>>        ClassLoader loader =
>>> Thread.currentThread().getContextClassLoader();
>>>        Enumeration<URL> resources;
>>>        try {
>>>            resources =
>>> loader.getResources("freemarkerTransforms.properties");
>>>        } catch (IOException e) {
>>>            Debug.logError(e, "Could not load list of
>>> freemarkerTransforms.properties", module);
>>>            throw UtilMisc.initCause(new
>>> InternalError(e.getMessage()), e);
>>>        }
>>>        while (resources.hasMoreElements()) {
>>>            URL propertyURL = resources.nextElement();
>>>            Debug.logInfo("loading properties: " + propertyURL, module);
>>>            Properties props =
>>> UtilProperties.getProperties(propertyURL);
>>>            if (props == null || props.isEmpty()) {
>>>                Debug.logError("Unable to locate properties file " + propertyURL, module);
>>>            } else {
>>>                loadTransforms(loader, props, newConfig);
>>>            }
>>>        }
>>> 
>>>        return newConfig;
>>>    }
>>> 
>>> 
>>> and in the same class we use this static method to render the template:
>>> 
>>>    public static Environment renderTemplate(Template template,
>>> Map<String, Object> context, Appendable outWriter) throws TemplateException, IOException {
>>>        // make sure there is no "null" string in there as FreeMarker will try to use it
>>>        context.remove("null");
>>>        // Since the template cache keeps a single instance of a
>>> Template that is shared among users,
>>>        // and since that Template instance is immutable, we need
>>> to create an Environment instance and
>>>        // use it to process the template with the user's settings.
>>>        Environment env =
>>> template.createProcessingEnvironment(context, (Writer) outWriter); 
>>> // NOTE: this is where the process blocks in a deadlock
>>>        applyUserSettings(env, context);
>>>        env.process();   // NOTE: this is where the process blocks in a deadlock
>>>        return env;
>>>    }
>>> 
>>> Jacopo
>> 
>> -- 
>> Best regards,
>> Daniel Dekany

-- 
Best regards,
 Daniel Dekany


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