Monday, December 5, 2011

How to watch YouTube videos offline (on OS X)?

Lately I have been traveling a lot, and I was not able to access the internet all the time; but I still want to look at some YouTube video, for example the greate Google I/O Sessions...

My needs are simple :

  • running on OS X (Lion)
  • download the video easily
  • no need to convert the file (to be able to read the file as soon as possible)
  • free
After some basic research, I found an easy way to achieve this using the following softwares:

Sunday, November 20, 2011

Installing Memcached on Mac OS X and using it in Java


In this article I will explain how you can:

  1. Install and Configure Memcached on Mac OS X
  2. Use Memcached in your Java Application

I won't go in too much detail about the benefits of using a distributed cache in your applications, but let's at least provide some use cases for applications that are running in the context of an enterprise portal, eXo Platform in my case - surprising isn't? And I will show this in another post.

We have many reasons to use a cache (distributed or not), in the context of enterprise portal, let's take a look to some of these reasons:

  • A portal is used to aggregate data in a single page. These data could come from different sources : Web Services, Database, ERP, ..... and accessing the data in real time could be costly. So it will be quite interesting to cache the result of the call when possible.
  • If the portal is used to aggregate many data from many sources, it is sometime necessary to jump into another application to continue some operation. A distributed and shared cache could be used to manage some context between different applications running in different processes (JVM or even technologies)
These are two example where a shared cache could be interesting for your portal based applications, we can find many other reason.

Note that the Portlet API (JSR-286) contains already a cache mechanism that cache the HTML fragment, and that eXo Platform also provide a low level cache, based on JBoss Cache.

Installation and Configuration

Installing Memcached from sources

You can find some information about Memcached installation on the Memcached Wiki. The following steps are the steps that I have used on my environment.

As far as I know, Memached is not available as package for Mac OS X. I am still on Snow Leopard (10.6.8), and I have installed XCode and all development tools. I have use the article "Installing memcached 1.4.1 on Mac OS X 10.6 Snow Leopard" from For simplicity reason I have duplicate the content and updated to the latest releases.

1. Create a working directory :

$ mkdir memcachedbuild
$ cd memcachebuild

 2. Install libevent that is mandatory for memcached

$ curl -O
$ tar xzvf libevent-1.4.14-stable.tar.gz
$ cd libevent-1.4.14-stable
$ ./configure
$ make
$ make verify
$ sudo make install  

3. Install memcached

Go back to your install directory (memcachedbuild)

$ curl -O
$ tar xzvf memcached-1.4.10.tar.gz
$ cd memcached-1.4.10
$ ./configure
$ make
$ make test
$ sudo make install 
You are now ready to use memcached that is available at /usr/local/bin/memcached

This allows you to avoid changing to the pre-installed memcached located in /usr/bin, if you want to replace it instead of having you own install, just run the configure command with the following parameter:  ./configure --prefix=/usr

Starting and testing Memcached

Start the memcached server, using the following command line:

$ /usr/local/bin/memcached -d -p 11211

This command starts the memcached server as demon (-d parameter), on the TCP port 11211 (this is the default value). You can find more about the memcached command using man memcached.

It is possible to connect and test your server using a telnet connection. Once connected you can set and get object in the cache, take a look to the following paragraph.

$ telnet 11211
Connected to tgrall-server.
Escape character is '^]'.
set KEY 0 600 16
This is my value
get KEY
This is my value

The set command allows you to put a new value in the cache using the following syntax:

set <key>  <flags> <expiration_time>  <number_of_bytes> [noreply] \n\n

  • key : the key used to store the data in the cache
  • flags : a 32 bits unsigned integer that memcached stored with the data
  • expiration_time : expiration time in seconds, if you put 0 this means no delay
  • number_if_bytes : number of bytes in the data block
  • noreply : option to tell the server to not return any value
  • value : the value to store and associate to the key.
    This is a short view of the documentation located in your source directory /memcachedbuild/memcached-1.4.10/doc/protocol.txt .

    The get command allows you to access the value that is associated with the key.

    You can check the version of memcahed you are running by calling the stats command in your telnet session.

    Your memcached server is up and running, you can now start to use it inside your applications.

    Simple Java Application with Memcached

    The easiest way to use memcached from your Java applications is to use a client library. You can find many client libraries. In this example I am using spymemcached developped by the people from Couchbase.

    1. Adding SpyMemcached to your Maven project

    Add the repository to you pom.xml (or you setting.xml)

        <name>Spy Repository</name>

    then the dependency to your pom.xml


    2. Use SpyMemcache client in your application

    The following code is a simple Java class that allows you to enter the key and the value and set it in the cache.

    import java.util.Date;
    import java.util.logging.Level;
    import java.util.logging.Logger;
    import net.spy.memcached.AddrUtil;
    import net.spy.memcached.MemcachedClient;
    public class Test {
        public static void main(String[] args) {
           try {
               System.out.print("Enter the new key : ");
               BufferedReader reader = new BufferedReader( new InputStreamReader(;
               String key = null;
               key = reader.readLine();
               System.out.print("Enter the new value : ");
               String value = null;
               value = reader.readLine();
                MemcachedClient cache = new MemcachedClient(AddrUtil.getAddresses(""));
                // read the object from memory
                System.out.println("Get Object before set :"+ cache.get(key)  );
                // set a new object            
                cache.set(key, 0, value );
                System.out.println("Get Object after set :"+ cache.get(key)  );
            } catch (IOException ex) {
                Logger.getLogger(Test.class.getName()).log(Level.SEVERE, null, ex);

    So when executing the application you will see something like :

    Enter the new key : CITY
    Enter the new value : Paris, France
    2011-11-16 15:22:09.928 INFO net.spy.memcached.MemcachedConnection:  Added {QA sa=/, #Rops=0, #Wops=0, #iq=0, topRop=null, topWop=null, toWrite=0, interested=0} to connect queue
    2011-11-16 15:22:09.932 INFO net.spy.memcached.MemcachedConnection:  Connection state changed for
    Get Object before set :null
    Get Object after set :Paris, France

    You can also access the object from a Telnet session:
    get CITY
    VALUE CITY 0 13
    Paris, France

    You can use any Java class in your application, the only thing to do is to make this class serializable.

    This is it for the first post about memcached and Java,  I am currently working on a small example integrating Web Services call, Portlets and memcached.

    Friday, September 2, 2011

    JAX-RS: Jersey and JSON single element arrays

    Last week I have been struggling with a small issue while developing a service using Jersey. The goal of this service is to provide JSON object to my Web application, so called directly from the browser. This service returns in a JSON array a list of Employees, something like:

    So an "employee" array, this is perfect and expected, but when my service returns a single element the returned object looks like:
    As you can see brackets [...] are missing around the employee item. This is an issue since your client code is expecting an array.

    A solution...

    My application is using Jersey, the JAX-RS Reference Implementation, and JAXB for the serialization of Java Objects to JSON, as I have explained in a previous blog post. I found a solution to this by creating a new JAXB Context Resolver. In this resolver I can control how the JSON object should be generated, here is my implementation :
    import com.grallandco.employee.service.converter.EmployeeConverter;
    import javax.xml.bind.JAXBContext;
    import com.sun.jersey.api.json.JSONConfiguration;
    import com.sun.jersey.api.json.JSONJAXBContext;
    public class JAXBContextResolver implements ContextResolver < JAXBContext > {
        private JAXBContext context;
        private Class[] types = {EmployeeConverter.class};
        public JAXBContextResolver() throws Exception {
            this.context = new JSONJAXBContext(JSONConfiguration.mapped().arrays("employee").build(),
        public JAXBContext getContext(Class objectType) {
            for (Class type : types) {
                if (type == objectType) {
                    return context;
            return null;
    First of all I declare this new class as a @Provider to say that it this class is of interest to the JAX-RS runtime. I put in the types array the list of the Java classes that are concerned by the serialization (line#13). Then I create the ContextResolved with the different options that fulfill my requirements. You can take a look to the JAXBContextResolver Javadoc to see all the possible options available. With this class, the service now returned the following JSON String:
    You can find a complete example (NetBeans project) here.

    Wednesday, August 31, 2011

    How to create a new Content List Template for eXo Platform 3


    eXo Platform provide many powerful features to manipulate and expose any type of content on a page. This is due to the fact that eXo stores the all the content in its Java Content Repository (JCR) and render the content on a page using Groovy Templates.

    In this how to you will learn how you can create and use template that are used in the "Content List" portlet. For example in the ACME sample site you can show the content in 1 or 2 columns just by selecting different templates.

    One Column View

    Two Columns View

    Creating a new Content List Template

    In this section you will learn how to create a new template using the eXo IDE. Before writing the new template it is important to learn where the templates are stored.

    eXo Content Service: Template Storage

    Like many things inside eXo Platform, the eXo JCR is used to stored the templates. Templates are just a special type of content. This allows developers to easily write and test code without having complex deployment process, but also it make the life easy to export a running configuration to another one. For this you just need to use the standard JCR export/import features.
    All the template and eXo Content Service configurations are stored inside a specific JCR workspace named : dms-system.
    Each template type (Document Type, Content List, ....) is stored in a specific location. In our case we want to work on the "Content List" portlet so the template are stored inside the following folder:
    • /exo:ecm/views/templates/content-list-viewer/list/

    Just for the fun of it, let's inspect this folder using the eXo CRaSH utility. If you are not interested you can jump to the next section. CRaSH is a shell for Java Content Repositories, the source of CRaSH is available on Google Code. So in a terminal window:
    1. Connect to CRaSH using telnet client:
      telnet 5000

    2. Connect to the JCR workspace using the following command:
      connect -u root -p gtn -c portal dms-system
      Where: -u is the user, -p the password, -c the Portal Container, and dms-system the workspace to use

    3. Move the the folder that contains all the templates for the Content List portlet:
      cd /exo:ecm/views/templates/content-list-viewer/list/

    4. List all the templates using the ls command

    You can see the list of all the templates available for the Content List portlet.

    Create a new template using the eXo IDE

    Let's now create a new template using the IDE. For this be sure you are connected with a user that is part of the /Developer group. For simplicity reason I am using the root user.

    The first important step is to go the the template location using the following steps:
    1. Access the IDE: click on My Spaces > IDE.

    2. Switch dms-system workspace: In the IDE menu click My Spaces >on Window > Select Workspace. And select the dms-system location in the dialog box and click OK.

    3. In the file structure on the left navigate to the template location :

    4. Create a new template : In the IDE Menu click on File > New > Groovy Template

    5. Save the file as "MyNewTemplate.gtmpl"

    6. Enter some basic code:
      <h1>This is my template</h1>
      The date is <= new Date()>

    7. Save the template

    8. Go back to the Home page of the Acme Site

    9. Switch to Edit more by selecting Edit in the top right drop down list.

    10. Move you mouse at the top of the list of news and click on the preference button:

    11. In the list of templates, select the "MyNewTemplate", and click save.
    We have created our new template, and use it on a page. We should now add some more interesting code to the template to really loop over the content based on the portlet configuration. But before this it is important to talk about caching and code modification.

    eXo Template and Cache

    To improve performances and a running system, the compiled version of the template is by default cached. This is why when you are modifying a template you do not see any change. We have two ways to work around this:
    • Run eXo Platform in Debug mode, in this case nothing is cached
    • Invalidate the cache manually using JMX
    Since working with no cache at all is not an option, here is the MBean you have to use to invalidate the Template Service cache:
    • exo:portal="portal",service=cache,name="TemplateService", then call the clearCache operation on it
    I do use JConsole for this, but you can use any method to call your MBeans operation.

    Do not forget to call this operation each time you modify your template to be sure eXo recompile the template.

    Accessing Content in the template

    The current code of the template is really simple, you need now to add code to print the content in the page. For this we will be using some eXo Content programming, once again in the IDE.
    If you are not interested to have detailed explanation of the code you can go to the complete source code here.
    The template used by the Content List portlet is based on the following Java class org.exoplatform.wcm.webui.clv.UICLVPresentation, this class is responsible to set the complete context that you can use in the template such as:
    • The folder or category that contains the content to show. The "Folder Path" field in the preference screen
    • The display settings: title, number of documents, elements to show, ...
    Here is the code to access these preferences:
        // import all the classes need in the template
        import javax.jcr.Node;
        import org.exoplatform.wcm.webui.paginator.UICustomizeablePaginator;
        import org.exoplatform.wcm.webui.clv.UICLVPortlet;
        import org.exoplatform.wcm.webui.Utils;
        // get the portlet preferences
        def header = uicomponent.getHeader();
        def isShowRssLink = uicomponent.isShowRssLink();
        def isShowHeader = uicomponent.isShowField(UICLVPortlet.PREFERENCE_SHOW_HEADER);
        def isShowRefresh = uicomponent.isShowField(UICLVPortlet.PREFERENCE_SHOW_REFRESH_BUTTON);      
        def isShowTitle = uicomponent.isShowField(UICLVPortlet.PREFERENCE_SHOW_TITLE);
        def isShowDate = uicomponent.isShowField(UICLVPortlet.PREFERENCE_SHOW_DATE_CREATED);
        def isShowLink = uicomponent.isShowField(UICLVPortlet.PREFERENCE_SHOW_LINK);
        def isShowReadmore = uicomponent.isShowField(UICLVPortlet.PREFERENCE_SHOW_READMORE);
        def isShowImage = uicomponent.isShowField(UICLVPortlet.PREFERENCE_SHOW_ILLUSTRATION) ;
        def isShowSummary = uicomponent.isShowField(UICLVPortlet.PREFERENCE_SHOW_SUMMARY);   
    The uicomponent object is defined by the container class of the portlet that calls the template. This class contains many utility methods. In the code above I retrieve all the preferences of the portlet, since the name are self-explanatory it is not necessary to detail them, especially when you look at the preferences screen below:

    Now that the template has all the preferences, it is time to loop on the content on print the information.
    The eXo Content Service provides API to manipulate the content, including pagination of content. The idea behind this is to let the Content Service manage the JCR query, sorting, caching and pagination of data. So in your template you will mainly manage two classes to loop through the content to show:
    • uicomponent.getUIPageIterator() a paginator object that is configured based on the portlet preferences
    • uicomponent.getCurrentPageData() contains a list of the content (JCR Nodes) that should print on the current page
    So let's print all the content of the page as a simple HTML list:
      <% for (viewNode in uicomponent.getCurrentPageData()) { def title = viewNode.getProperty("exo:title").getString(); print("
    • $title
    • "); } %>
    Just copy this code in your template, save it, refresh the cache... and go to your page. You should see the list of the content in a simple HTML list.
    On each content (Node), eXo Content API provides some helper method to easily manipulate the content and avoid using the JCR API directly. In the following code you can see the most important methods accessing content properties:
            def itemName = viewNode.getName();
            def itemLink = uicomponent.getURL(viewNode);  
            def webdDavLink = uicomponent.getWebdavURL(viewNode);    
            def itemDateCreated = uicomponent.getCreatedDate(viewNode);
            def itemModifiedDate = uicomponent.getModifiedDate(viewNode);
            def itemAuthor = uicomponent.getAuthor(viewNode);     
            def imgSrc = uicomponent.getIllustrativeImage(viewNode);
            def itemTitle = uicomponent.getTitle(viewNode);
            def itemSummary = uicomponent.getSummary(viewNode);
    One important point is the fact that these methods are responsible of many things, for example: formatting dates, returning complete URLs depending of the context of the portlet.
    Based on these methods you can now work on the presentation of the information on the page. Let's for example print the image, the title and allow user to click on the title to go in the detail view of the article. This is done simply using the following code:
      for (viewNode in uicomponent.getCurrentPageData()) {
        def itemName = viewNode.getName();
        def itemLink = uicomponent.getURL(viewNode);  
        def webdDavLink = uicomponent.getWebdavURL(viewNode);    
        def itemDateCreated = uicomponent.getCreatedDate(viewNode);
        def itemModifiedDate = uicomponent.getModifiedDate(viewNode);
        def itemAuthor = uicomponent.getAuthor(viewNode);     
        def imgSrc = uicomponent.getIllustrativeImage(viewNode);
        def itemTitle = uicomponent.getTitle(viewNode);
        def itemSummary = uicomponent.getSummary(viewNode);


    <% } %>
    For simplicity reason, this code does not manage any null value. Also the template do not deal with the portlet preferences such as the "Header", "RSS" links and so on, do not hesitate to do it if you want. The Web site should look like the following image:

    The last important point is to add the support for the in context editing that allows the user to edit the content directly from the template. Once again this is done with a method of the uicomponent object, that create a DIV around the content. Let's add this to the template:
      for (viewNode in uicomponent.getCurrentPageData()) {
        def itemName = viewNode.getName();
        def itemLink = uicomponent.getURL(viewNode);  
        def webdDavLink = uicomponent.getWebdavURL(viewNode);    
        def itemDateCreated = uicomponent.getCreatedDate(viewNode);
        def itemModifiedDate = uicomponent.getModifiedDate(viewNode);
        def itemAuthor = uicomponent.getAuthor(viewNode);     
        def imgSrc = uicomponent.getIllustrativeImage(viewNode);
        def itemTitle = uicomponent.getTitle(viewNode);
        def itemSummary = uicomponent.getSummary(viewNode);
    <%=uicomponent.addQuickEditDiv("MyTemplateContentEditor", viewNode)%>


    $itemSummary < /div>
    <% } %>
    The lines 15 and 19 are new in this template and provide support for Quick Edit feature.

    Done! We have created a new template for eXo Platform Content Service using embedded IDE.


    In this article you have learned how to create a new template for eXo Content Service, with some basic steps:

    • Create a new Groovy Template using the eXo IDE
    • Edit this template using the eXo Java Content API
    • Configure your Content List portlet instance on a page to select the new template

    You can now create your own templates and use your imagination to add cool features to your site (for example the carrousels you see on the eXo site are using custom CLV template.)

    Monday, April 11, 2011

    How to protect your REST service and Gadget in eXo Platform

    During a partner workshop I was showing to the developers how the eXo IDE can help them to develop new features quickly and push them to the users in few minutes. A person asked me if it is possible to put some restriction in services and gadgets based on user profile.
    As you can guess the answer is YES WE CAN!

    • How to access the security context in a REST service
    • How to check is a user is member of a group and manage permission from this information
    • How to consume this service in a gadget and leverage the security to protect resources
    If you are not interested to follow steps by step the explanations you can directly jump to the complete REST Service code or download the full eXo IDE Project from GitHub

    Access the User Profile from your REST Service

    As you probably know eXo Platform uses JAX-RS as API to develop and deploy REST Services. eXo developers can create REST services using their favorite Java IDE, but here I am using the eXo IDE package with eXo Platform.

    To access the security and user information in your service method it is possible to use the SecurityContext class of the JAX-RS API. Your method signature will look like:
    public class SystemInformationService {
      public Response getSystemInfo(@Context SecurityContext sc) {
        return Response.ok("foo", MediaType.APPLICATION_JSON).build();    
    In lines 7 and 8, I import the classes needed to inject the security context in the method getSystemInfo() in line 16. For now let's forget about the other part of the code.
    With the Security Context object you can now access many things in your code. Two methods are quite interesting for this example: getUserPrincipal() and isUserInRole(), since our goal is to check if a user is allowed to execute or not a part of the business logic.
    It is important here to remember that we cannot directly use the isUserInRole() method since this method uses the logical JavaEE roles that are defined at the Java application level. In our case we are interested to know if a user is present in a "eXo User Identity" Group, for example member of the /platform/administrators group. This information is populated during the login process and comes from the user provider that could be LDAP, the eXo Database or JCR, or any other source since developers can extend this API to plug their own provider.
    Let's create an helper method that check, using the eXo Identity Service, if the user that executes the method is present in a group.
    import org.exoplatform.container.ExoContainer;
    import org.exoplatform.container.ExoContainerContext;
    import org.exoplatform.container.component.ComponentPlugin;
      private boolean isMemberOf(String username,String group) {
        ExoContainer container = ExoContainerContext.getCurrentContainer();
        IdentityRegistry identityRegistry = (IdentityRegistry) container.getComponentInstanceOfType(IdentityRegistry.class);
        Identity identity = identityRegistry.getIdentity(username);
        return identity.isMemberOf( group );
    So this method is quite simple, it takes as parameter:
    • the name of the user, that you can get from the UserPrincipal.getName() method
    • the eXo Group you want to check, for example /platform/administrator
    You can now call this method from your resource to check the user, and code the "permission business logic". The method could now looks like:

      public Response getSystemInfo(@Context SecurityContext sc) {
        String groupToCheck = "/platform/administrators";
        String response = "";
        if (sc.getUserPrincipal() == null || !this.isMemberOf(sc.getUserPrincipal().getName(), groupToCheck) ) {
          response = "NOT-ALLOWED";
        } else {
          response = "ALLOWED";
        return Response.ok(  response   , MediaType.APPLICATION_JSON).build();
    In this example for simplicity reason I have hard coded the group to check, you can obviously use smarter code to user external configuration to inject a list of group to check for example. I manage the security logic of my method using simple if statement and return a string. You can also depending of your needs, manage the status of your response and use HTTP Code for example return an HTTP 403. For this you just need to return a different response using following code:
        return Response.status(Response.Status.FORBIDDEN).build();
    For simplicity reason I will stay with a single Response status (OK) and manage the permission in my client code.

    Complete REST Service

    Let's take a look to the full service now, this service allows administrators to get the list of the System Properties, other users get an status string "NOT-ALLOWED":
    import org.exoplatform.container.ExoContainer;
    import org.exoplatform.container.ExoContainerContext;
    import org.exoplatform.container.component.ComponentPlugin;
    public class SystemInformationService {
      public Response getSystemInfo(@Context SecurityContext sc) {
        String groupToCheck = "/platform/administrators";
        SimpleResponseWrapper response = new SimpleResponseWrapper();
        String status = "";
        if (sc.getUserPrincipal() == null || !this.isMemberOf(sc.getUserPrincipal().getName(), groupToCheck) ) {
          response.status = "NOT-ALLOWED";
          } else {
            response.status = "OK";
   = System.getProperties();
           CacheControl cacheControl = new CacheControl();
           return Response.ok(  response   , MediaType.APPLICATION_JSON).cacheControl(cacheControl).build();    
          private boolean isMemberOf(String username,String role) {
            ExoContainer container = ExoContainerContext.getCurrentContainer();
            IdentityRegistry identityRegistry = (IdentityRegistry) container.getComponentInstanceOfType(IdentityRegistry.class);
            Identity identity = identityRegistry.getIdentity(username);
            return identity.isMemberOf( role );
    public class SimpleResponseWrapper {
          String status;
          Object data;
    To summarize:
    • Line 24 : the SecurityContext is injected to the method
    • Line 26 : Initialization of a simple ResponseWrapper defined on line 51, that contains a status and data. That will be serialized in JSON by the eXo REST engine.
    • Line 28 : the method check if a user is connected and member of /platform/administrator. If not it send response with the status NO-ALLOWED.
    • Line 31/32 : The response object is sent. This response contains an OK status and the data (system properties list)
    • Line 42 : Using the eXo Identity Service, the method check if the connected user is member of a specific group.

    Consume the service into a Gadget

    I can now take this service and consume it into an Gadget. I also develop this Gadget using the eXo IDE.
    The following code shows the Javascript part of the Gadget that calls the service, check the security and push the response content in Gadget body. For productivity I use JQuery framework.
    Here some quick explanation about this code:
    • Line 23: To call the REST service, I use the $.getJSON() method. This method is really easy to use when you are executing the Gadget is in the same container than the portal that consumes it. When you are using the is interesting to proxy a request and you need to re-authenticate, for example using oAuth.
    • Line 3 : This is the call back method, as you can see in this method I use the ResponseWrapper to check the code in the status attribute. Depending of the status OK or not I do print the value.


    In this how-to you have learned how to:
    • Get the security context in your REST Service
    • Check the membership of a user using the eXo Identity Service
    • Create a gadget that consume this service and expose only data to user with correct profile
    • Download the full project from GitHub

    Wednesday, March 16, 2011

    eXo Cloud IDE : develop for the Cloud on the Cloud

    Yesterday, eXo has launched a new cloud based service: the eXo Cloud IDE. This IDE is an online service that facilitates the development of gadgets and mashups that could be deployed directly to a PaaS.

    Before launching this service on the Cloud we, eXo team and customers, have used the IDE embedded in the eXo Platform to extend our intranet and customer deployments (some of the modules that we have developed live on our intranet are available as plugins on the eXo Resource Center).
    This IDE is the last mile between the users and the developers. It provides a way to add new services asked by business users at a lower cost with a good time to market. And all this based on standards that corporate and Web developers like : REST Services using JAX-RS and UI based on OpenSocial gadgets in which you can leverage all the cool and powerful features of HTML5.

    What eXo has launched yesterday is a big step for developers since you can now develop, test and deploy your gadgets and services online, and this in your "personal environment" using eXo Cloud IDE supports multi-tenancy. I won't go in all the features of the IDE since you can test it yourself by joining the beta program and look at this video:

    eXo Cloud IDE resources:

    Tuesday, March 1, 2011

    How to calculate the size of a folder in JCR (Java Content Repository)?

    Today I was working with a partner in Paris and he wanted to know how to calculate the size of a specific folder in the eXo Java Content Repository (JCR).

    For this specific need the goal is to calculate the size of all the documents stored inside a specific location in the content repository. This could be used for example to manage quotas, estimate the size of a shared or personal storage, ... For this specific sample I will only take in consideration the size of the binary part of the document stored in the repository; this means I will not pay attention to the various attributes and meta-data that are also stored, neither the full text index created by Lucene that is embedded in eXo JCR.

    How the files are stored in the JCR?

    Files are stored in eXo JCR in the standard node type nt:file (and nt:resource). So for this example I will simply list all the nt:file of a folder and aggregate the size of the file itself. It is important to understand how JCR is storing the binary content. The best way to understand it, is to view it. For that I am using the print information given by  CRaSH, a shell for content repository developed by eXo team and lead by Julien Viet. Here the structure of a PDF document :

    | +-jcr:primaryType: nt:file
    | +-jcr:mixinTypes: [mix:referenceable,mix:versionable]
    | +-jcr:uuid: '6b89b6f0c0a8006530a8617df51bb0d7'
    | +-jcr:created: 2011-02-28T10:11:50.770+01:00
    | +-/Groups/spaces/intranet_v2/Documents/Technical/jsr170-1.0.pdf/jcr:content

    As you can see in this node the 'binary' is not visible, nothing bad here. As written in the specification in the section nt:file, the binary content is an attribute of the child node jcr:content that is exposed below:
    | +-jcr:primaryType: nt:resource
    | +-jcr:mixinTypes: [exo:owneable,exo:datetime,dc:elementSet]
    | +-jcr:uuid: '6b89b6f7c0a80065735b1a8853d389d0'
    | +-jcr:data: 
    | +-jcr:encoding: 'UTF-8'
    | +-jcr:lastModified: 2011-02-28T10:11:50.767+01:00
    | +-jcr:mimeType: 'application/pdf'

    You can see now that the jcr:content contains some interesting attributes:
    • jcr:mimeType
    • jcr:data this is where the binary content, the PDF itself , is
    So using the JCR API you just need to get the content length using the following java code:

    This returns the number of bits of the binary data. So to calculate the size of a folder you just need to navigate in all the documents (nt:file or jcr:content) and cumulate the size of all the files. In this following code, I am calculating the size of the folder "/Documents" by navigating into all the files contains in this folder and subfolders. (I could have chose to query all the jcr:content type instead of nt:file)

       Session session = getSession(); // use RepositoryService or context to get a session
       QueryManager manager = session.getWorkspace().getQueryManager();   
       String queryStatement = "select * from nt:file where (jcr:path LIKE '/Documents/%')";
       Query query = manager.createQuery(queryStatement, Query.SQL);
       NodeIterator nodeIterator = query.execute().getNodes();
       Node node = null;
       long totalSizeInMb = 0;
       while (nodeIterator.hasNext()) {
         node =;
         totalSizeInMb = totalSizeInMb + node.getProperty("jcr:content/jcr:data").getLength() / (1024*1024);

    As you can guess since we are navigating in the hierarchy you have to be very careful when using such query. This example is just a simple code sample to show you some of the cool features provided by the JCR API.

    Sunday, January 2, 2011

    iOS 101: How to convert a String to a NSDate

    During my vacations, I took some time to play with iOS development. I have been struggling with many small issues... This is the price to pay when learning a new technology, and this is part of the fun of doing it. I will try to document some of these issues in articles...  Let's start with a very common story : working with date.

    Objective-C and iOS SDK provide a class to help formatting date (marshaling and unmarshaling), this class is NSDateFormatter. No surprise, the NSDateFormatter uses the Unicode Date Format Patterns.

    A small example of date creating from a string:

        NSDateFormatter *dateFormatter = [[NSDateFormatter alloc]init];
        [dateFormatter setDateFormat:@"yyyy-MM-dd"];
        NSDate *date = [dateFormatter dateFromString:publicationDate ];
        [dateFormatter release];
         // use your date object

    The date that I have to create from a sting looks like "2010-11-12". So I do not have any time information. When I do convert this string with the code above, the result is  "2010-11-11 23:00:00 +0000". As you can see the date is calculated from my current time zone, small reminder I am in France. So the "date" object itself is perfectly fine, but in my example I want to have the date independently of the time.

    To be able to manage the date without any time/timezone information, I can force the timezone I want to use when using the  NSDateFormatter class. I just need to use the setTimeZone instance method.
    The code looks like that now (see line#3):
        NSDateFormatter *dateFormatter = [[NSDateFormatter alloc]init];
        [dateFormatter setDateFormat:@"yyyy-MM-dd"];
        [dateFormatter setTimeZone:[NSTimeZone timeZoneForSecondsFromGMT:0]];
        NSDate *date = [dateFormatter dateFromString:publicationDate ];
        [dateFormatter release];
         // use your date object

    Hope that helps!