Posts tagged howto

It has been some time since last post about import scripts from external sources to alfresco repository, I was busy with debugging and threading, but now I have some little time to write some notes on that topic again. I’d like to introduce „architecture“ of my solution, at least a first part of it, so lets start with an image.

Calling ImportAction

MainImportingThread is Runnable implementation, which is initiated on init. Main thread sleeps some time and searches for config files in repository, while not sleep. If found some, ImportActionTask instance is created for each config in separate thread. ImportActionTask checks, if is it possible to run script described by config. If so, run script method on ImportAction is executed. That’s in few words functionality of the first part. Now in more details.

First version used quartz jobs triggered by org.alfresco.util.CronTriggerBean every 10 seconds, but that was temporarily solution, too heavy in my eyes. In second version I tried to use BatchProcessor, but spent few days without got it worked as I want :-(. Finally I used ThreadPoolTaskExecutor with combination of java.lang.Runnable in main thread and it worked like a charm! As I wrote a while ago, MainImportingThread has its own separate thread, which cyclically looks for configuration files in repository. It looks like following snippet:

public void init() {
    taskExecutor.execute(new Runnable() {
        @Override
        public void run() {
            while(keepAlive) {
                Thread.sleep(threadSleepMs);

                for(ResultSetRow row : resultSet) {
                    Object oTarget = pool.makeObject();

                    if(oTarget instanceof ImportActionTask) {
                        ImportActionTask importActionTask =  (ImportActionTask) oTarget;
                        importActionTask.setScriptRef(row.getNodeRef());
                        taskExecutor.execute(importActionTask);
                    }
                    pool.destroyObject(oTarget);
                }
            }
            taskExecutor.shutdown();
            pool.destroy();
        }
    });
}

For every row in result set PoolableObjectFactory creates a new instance of ImportActionTask and pass it to ThreadPoolTaskExecutor to execute. After all that – object is destroyed (destroyObject method is there just for sure – in time this method is called action still runs).

ImportActionTask is Runnable implementation, so every action runs its own thread. After execution isTimeToRun() method is called and action runs only when it’s its time and action is enabled, as it defined in data model illustrated on following diagram.

Config model

isTimeToRun() method uses fields importCron, importLastAction and isImportActive for its work. Its body looks similar to following simplified code snippet:

private boolean isTimeToRun() {
    if(!model.isImportActive())
        return false;

    String cronString = model.getImportCron();
    Date lastAction = model.getLastAction();

    CronExpression cronExpression = new CronExpression(cronString);
    if(cronExpression.getNextValidTimeAfter(lastAction).getTime() > System.currentTimeMillis())
        return false;

    return true;
}

Previous snippet checks cron expression against time of last successfully executed action using org.quartz.CronExpression and in case of success (ie lastAction+cron < current time) importAction itself may be triggered. But more on this next time, right now just another snippet from ImportActionTask, which calls importAction (received from ProxyFactoryBean):

public void run() {
    if(isTimeToRun) {
        try {
            importAction.invocateImportScript();
        } finally {
            importAction.clean();
        }
    }
}

In my last blogpost on this topic I wrote about invoking rhino scripts programatically from Alfresco and about passing its model into freemarker templates. After that I realized that alfresco templateService is unable to render more complex models (nested classes and collections) if called this way (please note on Alfresco webscripts invoked standard way this works correctly!). I think the problem is – no wrapper is used while passing model. I spent lot of time trying many things, read a lot of posts and topics on that, played with built-ins, trying to find that part in Alfresco source, but still no result, just exceptions. But solution is VERY SIMPLE – to write own templateService :-). Well, maybe this post is more about Freemarker and Rhino than Alfresco, sorry about that!

So, what I want to achieve? Suppose some simple script like this one:

model.bar="foo";
model.foo = "bar";
model.obj = {q:1, w:3, e:9};

model.arr = new Array();
model.arr[0] = {a:1, b:8, c:9, d:{d:66}};
model.arr[1] = {a:2, b:7, c:10, d:{d:66}};
model.arr[2] = {a:3, b:6, c:11, d:{d:66}};
model.arr[3] = {a:4, b:5, c:12, d:{d:66}};

and a Freemarker template simple as that:

q attribute: ${obj.q}

<#list arr?keys as value>
  - ${value} = ${arr[value].a} = ${arr[value].b} = ${arr[value].c}
  <#assign obj_d = arr[value].d>
  + d: ${obj_d.d}
</#list>

Now after calling templateService.processTemplate( . . . ) the output is Exception this and Exception that… That happens, because Rhino creates NativeObjects for those objects and after passing those objects to Freemarker (through Java – without any ObjectWrapper), which doesn’t know how to handle them. The same situation happens when passing a collection with generics like <String, Object> into model – those Objects are standard Java objects and in Freemarker acts like them, they really don’t have attributes like q, a, b, etc. :-). Similar situation can happen with collections – they needs to be wrapped too. But stop with theory, back to practise. For those interested in wrapping and so, follow Freemarker documentation on wrappers.

Before wrapping – when I printed out keys of model, there were’nt my attributes defined in Javascript. What I found inside is on following listing, note my attributes are also there – bar, foo, arr, obj:

<#assign keys = model?keys>
<#list keys as key>
 + ${key}
</#list>

(** output **)
 + getClass
 + clone
 + put
 + remove
 + get
 + equals
 + entrySet
 + class
 + hashCode
 + foo
 + keySet
 + size
 + clear
 + isEmpty
 + containsKey
 + values
 + arr
 + containsValue
 + empty
 + toString
 + putAll
 + bar
 + obj

Those properties belongs to hashMap and is possible to get rid of them using simpleMapWrapper, this technique is described well in Rizwan Ahmed post.

What about my templateService implementation? First I tried to use JSONtoFmModel and convert javascript objects to strings, but that was no way forward. That was before I discovered wrappers :-). There is RhinoWrapper class in Freemarker and it solves all my problems! It can be used as simple as this:

Configuration cfg = new Configuration();
RhinoWrapper rhinoWrapper = new RhinoWrapper();

rhinoWrapper.setSimpleMapWrapper(true);
cfg.setObjectWrapper(rhinoWrapper);

Previous listing creates new Freemarker configuration instance and rhino wrapper instance and binds them together. With that configuration it’s possible to create template instance, which takes reader with template content, let’s read it from repository:

NodeRef nodeRef = new NodeRef("workspace://SpacesStore/56ba2237-f776-494a-939b-d259b68c021a");

ContentReader contentReader = contentService.getReader(nodeRef, ContentModel.PROP_CONTENT);
InputStream inputStream = contentReader.getContentInputStream();

Template template = new Template("my_template", new InputStreamReader(inputStream), cfg);

That’s all we need to render. Rendering takes one more parameter – model map, which is HashMap defined in my previous blogpost. To keep it simple (and post a little shorter) I’m writing output to sysout:

OutputStreamWriter streamWriter = new OutputStreamWriter(java.lang.System.out);
template.process(rootMap, streamWriter);

Those few lines and everything works fine now! But I got some silver hairs with trying to solve that, now I can feel like a boss, so I achieved new „Alfresco guru badge“ :-). Also I’m thinking about some public GIT repository with my Alfresco inventions, what you think about it?

Like an Alfresco guru!

PostScriptum: Can anyone explain me why Alfresco uses Rhino version 1.6R7 which is from year 2007? :-O