Trial of Apache Sling

Introduction

Sling is based on Felix which is an implementation of OGSi. It includes Felix webconsole (http://felix.apache.org/site/apache-felix-web-console.html) bundle to make it easy to inspect OSGi framework. Also Sling integrates Jackrabbit and wraps it as an OSGi bundle. To update Java Content Repository, the client app can send regular HTTP POST requests. In other words, it exposes Java Content Repository in a REST way.
It can be run either independently or in a servlet container (e.g. Apache Tomcat).

Resources

Sling: http://sling.apache.org/site/index.html
Useful Sling help: http://felix.apache.org/site/apache-felix-framework-usage-documentation.html
Install and upgrade bundles in Felix web console: http://sling.apache.org/site/installing-and-upgrading-bundles.html
Address of Felix Management Web Console: http://ip_address:port/system/console/

When I clicked “Configuration” link on the top, Null Pointer Exception was thrown out.
It turns out that this is problem of Felix webconsole. See
http://issues.apache.org/jira/browse/FELIX-1135
http://issues.apache.org/jira/browse/FELIX-1028

This post contains some useful information http://groups.google.com/group/sakai-kernel/web/building-3akai-sling.

Solution

Download sling (standalone distribution) and unzip the tarball:
http://mirror.cc.columbia.edu/pub/software/apache/sling/org.apache.sling.launchpad.app-5-incubator-bin.tar.gz
Download new version of felix webconsole:
https://issues.apache.org/jira/secure/attachment/12407768/org.apache.felix.webconsole-1.2.9-SNAPSHOT.jar
Assume the new version of webconsole is downloaded to dir <DIR>

Execute following commands in the directory where sling tarball is unzipped.

jar xf org.apache.sling.launchpad.app-5-incubator.jar 
cd resources/bundles/5/ 
rm org.apache.felix.webconsole-1.2.8.jar 
cp <dir>/org.apache.felix.webconsole-1.2.9-SNAPSHOT.jar ./ 
jar cMf org.apache.sling.launchpad.app-5-incubator.jar resources META-INF org

Run the server:

java -jar org.apache.felix.webconsole-1.2.8.jar -p 4040

Note: you CANNOT use arbitrary new version of felix webconsole without updating other components of felix package. The reason is that different versions of felix console requires different versions of felix core/OSGi.

Misc.

If you are using both JCR Installer and Felix web console to update a bundle, you will get into trouble.
JCR installer:
    http://sling.apache.org/site/jcr-installer-jcrjcrinstall-and-osgiinstaller.html
    JCR installer tries to install OSGi bundles/modules found in Java Content Repository.
Bug
   “JCR Install prevents update of bundle through other channels like the web console”
    http://issues.apache.org/jira/browse/SLING-1106

Java Conent Repository - Jackrabbit

Resources

Wiki: http://en.wikipedia.org/wiki/Content_repository_API_for_Java
JSR 170: http://jcp.org/en/jsr/detail?id=170
JSR 170 API: http://www.day.com/maven/jsr170/javadocs/jcr-1.0/index.html
JSR 283 (JCR 2.0): http://jcp.org/en/jsr/detail?id=283 (in progress)
Jackrabbit: http://jackrabbit.apache.org/
List of Jackrabbit components: http://jackrabbit.apache.org/jackrabbit-components.html

Introduction

Jackrabbit implements JSR 170 and JSR 283.

• Wrap JCR to make it a WebDAV server so that WebDAC client can access it.
  Actually it is a fully featured WebDAV server backed by the JCR repository.
  Address for default repository: http://your_ip:your_port/repository/default/
  It seems that this method only exposes the file and directories in JCR. If you want more fine-grained access, use JCR remoting instead.
  Also see: http://jackrabbit.apache.org/standalone-server.html#StandaloneServer-WebDAVaccess
  http://jackrabbit.apache.org/jackrabbit-web-application.html
• JCR remoting
  Provides more fine-grained content access.
  Address for all workspaces of JCR repository: http://your_ip:your_port/server
  Also see: http://jackrabbit.apache.org/jackrabbit-web-application.html
• RMI access
  http://jackrabbit.apache.org/standalone-server.html#StandaloneServer-RMIaccess
• local access
  Through JNDI or servlet context.

Installation problem

When I tried to install Jackrabbit on gridfarm machine which uses NFS V3, I got problem described in this bug report (http://issues.apache.org/jira/browse/JCR-1605). Basically it says Jackrabbit needs some features that are not implemented in NFS prior to V4.