Java Applications on Privileged Ports

I am running most of my Java applications with Java Service Wrapper on Ubuntu. Most of these applications can run on unprivileged ports above 1024, e.g. Tomcats running behind an Apache http reverse proxy or the Openfire XMPP server that uses ports above 1024 by default. However there are exceptions like the LDAP server ApacheDS or Tomcats that do not require the features of httpd in front of them.

If you want to run Java applications on privileged ports below 1024 there are several options you can choose from:

To use authbind follow these steps:

Step 1: Install and configure authbind

Install authbind from the Ubuntu repository:

# aptitude install authbind

For each port your application should be able to bind to create a file in /etc/authbind/byport and make in executable by the user that runs your application. For ApacheDS I did the following:

# cd /etc/authbind/byport
# touch 389 636
# chown apacheds:apacheds 389 636
# chmod 700 389 636

This results in the following files:

# ls -l /etc/authbind/byport/
total 0
-rwx------ 1 apacheds apacheds 0 2010-05-04 21:24 389
-rwx------ 1 apacheds apacheds 0 2010-05-04 21:24 636

More information on access control is available in authbind (1).

Step 2: Update wrapper.conf

Authbind works by overloading the bind function in libc. This is done by setting the environment variable LD_PRELOAD. If you are using Java Service Wrapper the easiest way to do this is to add the following line to your wrapper.conf:


As authbind only supports IPv4 you must prevent your application from binding to the IPv6 port as well. This can be achieved by setting the system property in wrapper.conf:

That’s it!

This approach works with any Java application and is not limited to ApacheDS. Have a look at A Better Tomcat for Ubuntu and Debian by MuleSource to see how they are using authbind without Java Service Wrapper to make Tomcat run on standard HTTP ports.

Book Review: Modular Java

Modular Java by Craig Walls is a book on building modular Java applications on OSGi platforms.

Published in the Pragmatic Bookshelf series it keeps up to the standards of that great series by presenting content that matters in a format that makes you try it out immediately.

OSGi’s value proposition is to keep complexity in software products manageable. It keeps modules isolated from each other and encourages loose coupling through publishing and consuming services. You can think of OSGi as an incarnation of service oriented archietcure (SOA) within the Java Virtual Machine. OSGi has its roots in the embedded systems environment and became popular for desktop applications with Eclipse using it as their core infrastructure. From embedded to desktop OSGi is currently coming to the server side.

Craig’s book introduces the basics of OSGi, shows how it isolates modules by its unique approach to classpath handling and gives you an overview of the concept of OSGi services. One easy to follow example application is used consistently throughout the book to show the various aspects.
Most of the time the book uses Equinox as runtime but Felix and Knopflerfish are also mentioned. For building bundles Modular Java makes use of Pax especially Pax Construct. It does not mention Bundlor, Bnd or Tycho in depth. Especially the Maven based Tycho stack sounds really promising so it’s unfortunate that it isn’t covered. I guess however this is just an attribution to the current speed of development in the OSGi tooling space.

Spring Dynamic Modules are an attempt to bring the principles of Spring Framework to OSGi. In the spirit of Spring Framework Dynamic Modules (DM) build on proven solutions (OSGi in this case) and make them easier to use. They eliminate a lot of boilerplate code that is normally require to handle OSGi services that may appear and disappear at any time. Spring-DM also provides integration with Spring Application Contexts and has support for web applications through an extender. Spring-DM is covered really well by the book. An appendix describes the new OSGi Blueprint Services that are an attempt to standardize the ideas of Spring-DM. Spring’s new dm Server is not covered.

The book focuses on the core concepts and shows the benefits of using OSGi for application development. The target audience are experienced Java developers. It is very well written, easy and fun to read and serves as a great introduction. I recommend the book to Java developers who consider making use of OSGi in future projects.

Code Style: Final Arguments

Java allows you to make arguments final by declaring them as final in the argument list of the method declaration:

public void doSomething(final String foo)

This means that inside the method you cannot change what the argument reference points to, i.e. it prevents you from doing things like this:

  foo = "bar";

It is bad style to change the reference an argument points to. You should treat all arguments as if they were marked final. It would have even been a good idea to make this a language feature and have Java treat all arguments as final by default.

However does this justify to declare all arguments as final? Some people suggest this though I haven’t seen this in the wild very often.

The pros:

  • enforces not changing the reference an argument points to

    The cons:

    • makes method signatures longer and harder to read
    • takes longer to write, being lazy is a virtue

    There is one thing to note: Changing the reference the argument points to does not actually change the value of the caller’s variable passed to the method:

    public void testDoSomething()
      String foo = "foo";
      System.out.println(foo); // still prints "foo"
    public void doSomething(String foo)
      foo = "bar";

    However if you pass an object that is not immutable and you change the state inside the called method you actually do change the caller’s data. This is nothing a final modifier can prevent you from doing though it may be a source of trouble if not properly stated in the contract of the method.

    So to sum it up: You should not change the reference an argument points to as it causes confusion. You can prevent this by adding the final modifer. Doing so however clutters your code and thus shouldn’t be done (except when needed to use the argument in an inner class). Pay attention to not change the state of an object passed to a method if that’s not part of the method’s contract.

    The same applies to some extend to final local variables. Use them where they make your code easier to understand but not everywhere you could. If you are a fan of final have a look at Scala‘s val keyword.

SSO for RoundCube Webmail with Atlassian Crowd

Atlassian Crowd is a single sign-on and identity management tool by Atlassian that integrates well with their suite of software engineering and collaboration tools like JIRA, Confluence and Crucible. It offers a SOAP API that allows integration into arbitrary third-party systems. Integrating a webmail system with Crowd is quite easy. I’ve choosen RoundCube Webmail 0.2.2 as an example. RoundCube is based on PHP and has a nice and clean user interface and a well-written code base.

Step 1: Basic Integration

There is a PHP integration library that can be used as a starting point. It provides the methods for SSO but lacks the convenience of Crowd’s HttpAuthenticator. Implementing a simple PHP version of the HttpAuthenticator was the first step. My implementation uses APC to store the application token and validates every request with Crowd.

Step 2: Dovecot Masteruser

While the original version of RoundCube uses the user’s username and password to connect to the IMAP store that’s no longer possible with the crowdified version as it doesn’t have access to the user’s password. One solution is to use dovecot’s masteruser feature. With that configuration in place RoundCube can access the user’s mailbox by using its own password instead of the user’s password.

Step 3: Configuration

That’s it. Quite simple. If you like you can have a look at my patch. Check config/ and provide the username and password of your dovecot masteruser as well as the application name, credential and service URL for Crowd.

Nexus vs. Artifactory

Until now we didn’t use a repository manager for Maven. Our repos were a plain directory structure on the file system served by Apache. Uploading was done using Apache’s WebDAV capabilities with a simple authentication against our LDAP directory:

<Location /maven>
  Options Indexes

  DAV On
  AuthType Basic 
  AuthName "reucon Maven Repositories"
  AuthBasicProvider ldap
  AuthLDAPURL ldap://
  AuthLDAPBindDN uid=httpd,ou=techusers,o=myorg
  AuthLDAPBindPassword secret
  AuthzLDAPAuthoritative off

  Require valid-user
  FileETag None

We are maintaining four repositories: one for our public Open Source artifacts and one for proprietary internal artifacts along with corresponding snapshot repositories. Access to the internal repository was limited based on an IP address range.

There are multiple reasons for us to use a repository manager:

  • Unified access to repositories

    In the old days all you needed was the central repo (formerly known as ibiblio). Times have changed and now many of our projects require artifacts from a variety of different repositories. It seems many organisations prefer having their own repos instead of publishing to central. This includes SpringSource, JBoss, Codehaus and several snapshot repos like for Apache. Maintaing a list of these repos in each developers settings.xml is a pity and including them in the poms makes things even worse in the long run.
  • Finer grained access control
    On the one hand we need access to our internal repo from outside of our internal network, so IP based access control no longer works well. On the other hand not all developers should be allowed to publish releases. Some kind of role based access control was needed.
  • Automated creation of the Nexus index
    A Nexus index is basically a zip file containing a lucene index of the artifacts in a repository. Most Maven IDE plugins now support searching for artifacts when adding dependencies to a project. To make this work the IDE must be be able to download an up to date index of the repositories.
  • Web based artifact search
    You may know a web site to search for artifacts in the central repo. I’ve often used it to find the correct version and maven coordinates for a dependency. A similar solution for our internal repositories would be nice.

There are a lot more reasons to use a repository manager like faster builds through caching of artifacts, black- or whitelisting of artifacts based on corporate standards but those listed above were the key factors for us.

There are three products that can be used: Apache Archiva, Sonatype Nexus and JFrog’s Artifactory. There is a feature matrix
that shows their features.

I dropped Archiva because its development is rather slow and it is missing some important features like grouped repositories. So Nexus and Artifactory remained. I came across two blog postings from January:
Sonatype’s comparison and
JFrog’s response. Combined they provide a lot of insight. Here is my own comparison:


Good LDAP integration is a must have. Artifactory supports this out of the box, Nexus does not include LDAP support in its Open Source edition. It is a Nexus Pro feature. I do understand that Sonatype is trying to sell its Pro version but LDAP support is really a basic and vital feature. Fortunately it is not too difficult to implement a custom authenticator for Nexus and in fact there is already a project at Google Code called nexus-ldap that adds free LDAP support to Nexus. Both Artifactory and Nexus support fine grained role based authorization. One problem I faced with Artifactory was that requiring authentication seems to be a global setting, so you either require authentication for all repositories or for none. This is less flexible than Nexus which allows us to make our Open Source repository available without authentication and requires authentication only for deployment and for our internal repositories.
Artifactory has a nice additional feature that eliminates the need to store the user’s password in Maven’s settingx.xml in clear text by encrypting the password with a user specific key stored in Artifactory. This is an interesting approach and I would like to see this concept being used more widely (e.g. for Subversion).


How the repository manager stores artifacts and meta data is the biggest difference between Artifactory and Nexus. Artifactory uses a Java Content Repository (JCR) that can optionally be hosted in a MySQL database.
Nexus stores artifacts and meta data in the file system. It uses the maven layout so it is easy to access the repositories managed by Nexus externally. This becomes handy not only for migration but also when synchronizing to central through rsync. Though Artifactory offers an export feature having my repository data available directly on the file system makes me feel better.

Searching and Indexing

Both Nexus and Artifactory publish indexes (based on Lucene) and provide a web interface for searching artifacts stored in the repository. Nexus takes this one step futher and also allows searching for artifacts in proxied repositoreis not yet stores in the local repository. This is really handy and eliminates the need to use external sites to search for artifacts and they current version.


Before I found nexus-ldap I was about to choose Artifactory over Nexus. After that I prefer Nexus for the file system based storage and better searching.


Maven Release with Subversion 1.5 and 1.6

There is a problem with the maven-release-plugin when used with recent versions of Subversion. It stared at version 1.5.1 of Subversion and made the release:prepare command fail because Maven was no longer able to tag the release.

You may have encountered the following error with release:prepare:

svn: File '...' already exists

One reason for this can be SCM-406.

For some time I’ve worked around this issue by doing my releases on a machine with an older version of Subversion.

A better solution is to use the latest version of the maven-release-plugin (2.0-beta-9 at the moment) and set the remoteTagging property to true:

        <preparationGoals>clean install</preparationGoals>

Keep in mind that you should always specify the exact version of the plugins you are using. This not only makes sure you get what you need it also ensures that the build is reproducible in the future and works consistently accross different machines.

Security Issues Caused By External Hosting

Thomas has a nice example of how Deutsche Lufthansa has leaked personal data through an entertainment site operated by an external agency.

Most companies have strict rules for handling personal data and installed security policies for secure handling of sensitive information. Therefore enterprise data centers are usually quite secure. However the corporate processes that are required to keep the standards high are slow and expensive. This causes some companies to skip them in favor of faster and cheaper alternatives.

One solution is to accept hosting offers by the agencies that build the sites. The problem is that they are seldomly capable of providing a secure environment. It’s just not their business. The result is that sites with sensitive data are operated in shared hosting environments by unskilled persons out of control of corporate IT. It’s only a matter of time until security issues pop up and companies can be glad if they are informed before any data is stolen.

It just doesn’t make sense to harden the front door if you open up a few back doors at the same time. The best security policies are worthless if companies are willing to bypass them for faster and cheaper alternatives. Maybe Thomas’ story will help showing the value of corporate IT to those seeking alternatives without looking at the consequences.

Nokia E63

As DECT is mostly broken it was time for some new mobile handsets.

We are already using Asterisk for our communication so the new mobile handsets are required to work well with it. Communication should be secure and ideally the handset would also be a mobile (GSM) phone that could be carried along when leaving the office.

Our choice was the Nokia E63. It supports quad-band GSM, UMTS, SIP and WLAN IEEE 802.11b/g including WEP, 802.1X, WPA and WPA2. Combining GSM and SIP + WLAN works out great. In the office we directly receive landline and VoIP calls to our mobile. When we are away Asterisk detects the missing phone and either routes calls to the mobile number or sends callers to the mailbox.

The solution is affordable, based on open standards, secure and very user friendly.

JBoss Admin Console

JBoss AS 5.1.0-CR1 is out and finally includes a brand new admin console:

After installing JBoss AS 5.1.0 you can access it at http://localhost:8080/admin-console. Login with user “admin” and password “admin”.

The project behind the admin console is Embedded Jopr a web-based application for managing and monitoring an instance of JBoss AS. It is the little brother of Jopr. Jopr is a full-fledged systems management tool that helps managing and monitoring multiple instances of JBoss AS, Apache Webserver, Tomcat and more. The advantage of Embedded Jopr is that it is available out of the box and does not need any external resources like a database or separate agents. I am sure it makes operating JBoss AS a lot easier and more fun.

Give it a try and download the latest version.

The Ideal Development Workspace

After my old chair was more and more broken I decided to buy a new one. After some research I chose the Embody by Herman Miller.

The chair was delivered yesterday and it is just great. Its covering is like skin and lets the air flow through. The chair supports your movements and feels very comfortable.

For me this chair is part of the ideal workspace for software development which consists of

  • a fast computer with lots of memory
  • two big screens
  • a phone with good support for hands free calls
  • a cheap desk
  • a great chair
  • a calm environment
  • enough coffee