I’ve been sitting on this one for a while, finally getting around to publishing.
An example project where we have taken a Java library (java-xirr) and expose it as a REST service using JAX-RS. Then the service is dockerized using the maven dockerfile plugin. On the client side, we create a separate client using the Node.js connect server in order to illustrate various issues with CORS when utilizing REST services.
I finally took the plunge to migrate my old Blogger blog to the more convenient GitHub Pages. Like everybody else I found when googling this topic discovered, it wasn’t as easy as it seemed at first.
As an exercise in creating a Java library and submitting it to the Central Repository, I created an implementation of the xirr (irregular internal rate of return) function in Java.
Some XSLT re-usable templates for posterity:
New box, new OS, time for another edition of trying to connect to Microsoft's VPN software. This time it is Fedora's turn.
Just to get my feet wet, I published a Node.js module called xirr.
I recently upgraded from Ubuntu 14.04 on my main desktop machine and discovered that my VPN connection to Windows 2008 Server no longer worked. The bugaboo turned out to be the routing table which no longer requires a gateway entry. Here I have rewritten my post originally written for 12.10 to reflect the new configuration.
So if you have not been under a rock and have used Java 8, you are surely aware of the new String.join() method and the Collectors.joining() method to concatenate arrays or streams of Strings. Sometimes however, a simple concatenation with a delimiter is not quite up to the job.
Creating a custom implementation of java.stream.Collector seems daunting at first, but once you give it a try, you'll see that it can actually be pretty easy.
If you are not used to using lambdas and functional concepts, your first look at the Collector interface will be intimidating. From a pre-Java 8 perspective, there are four interfaces to implement to create a custom Collector implementation: java.util.function.BiConsumer, java.util.function.BinaryOperator, java.util.function.Function and java.util.function.Supplier. Fortunately they are all functional interfaces which will allow us to take some shortcuts with lambdas and functional expressions.
The example I chose to implement is a Collector for SetValuedMap from Apache's Common Collections project. We'd like a static method similar to the standard Collectors.toMap() method which will generate a Collector instance yielding a SetValuedMap implementation.
There are a lot of moving parts to the Collector in terms of generics. First, we will have generic parameters for the type in the existing stream <T>, the type of the key in the map <K> and the type of the values in the map <V>. Then we need to identify the three generic parameters to the Collector interface: <T> is the same as before, the type of objects in the stream; <A>, the accumulation type will be SetValuedMap<K,V>; and <R>, the result type, will also be SetValuedMap<K,V>. It is frequently the case with Collectors that <A> and <R> are the same.
Now that we have our generic ducks in a row, we can start figuring out our Collector implementation. For the supplier, we can use a constructor of a SetValuedMap implementation, e.g. HashSetValuedHashMap::new.
The accumulator will be a lambda function taking in a map and a stream object, it will need to put the stream object in the map. For that we will need to pass in functions converting the stream objects to keys and values respectively (just like in Collectors.toMap()).
The combiner will need to accept two maps and return a map containing entries from both. Again this can be specified with a lambda function.
We don't need anything beyond the identity function for the finisher, which means we ready to create our Collector implementation using the Collector.of() factory method:
This method can be used to create a version of Collectors.groupingBy() which eliminates duplicates simply by passing Function.identity for the valueMapper:
If we wanted to get really fancy we could also pass in a Comparator to use with our set, but I will leave that as an exercise for the reader.
See the file MoreCollectorsTest.java for some examples of these methods in action.
Just collecting the implicit objects defined by the JSF 2.2 specification (section 126.96.36.199, table 5-11) which are available in the EL:
Every once in a while when using jQuery UI I notice that my widget is not being initialized smoothly. For example, when using the menu widget I might see the list items behind the menu briefly. Then the page jumps around and it is a generally unpleasant experience for the user. Who likes it when your jQuery widgets are jumpy and cause the page to feel like one of those old 'punch the monkey' banner ads?
To add the conversation ID parameter
cid to a
persistent-sessions element to your WildFly configuration to keep sessions persistent across redeployments and restarts:
This post documents how to install and configure WildFly 8.2.0 on CentOS 6.6. We make some changes to move some of the configuration under /etc and also place log files under /var/log and temp files under /tmp just like a well-behaved POSIX application should.
We’ll start by installing Java; download your desired version as an RPM from Oracle and install:
I had a number of CentOS instances running under Hyper-V using the standard virtual network interface via integration services. Post CentOS 6.3 integration services are included in the install and that has been my experience. However at some point after updating to 6.6, something causes the integration services to no longer work with the virtual network interface.
To fix, remove the Network Adapter from the Hyper-V configuration and replace it with a Legacy Network Adapter.
Now you need to boot the virtual machine and access it from the Hyper-V console in order to log in. Backup the file
/etc/udev/rules/70.persisent-net.rules and remove it from the
/etc/udev/rules directory. This file tells CentOS to look for the old network interface and assign it to
Second, backup the
/etc/sysconfig/network-scripts/ifcfg-eth0 file. Edit the file and remove any reference to
Just a quick post in case you are trying to use a JSF page as a welcome file. This is what you'll need in your web.xml:
Recently I was porting a JEE application’s development environment from an outdated version of IDEA to Maven and NetBeans. After some effort I got the two builds to yeild pretty much the same EAR files.
I've had this one as a draft post for a while and I just ran into the it again, so it's time to to publish it.
Liferay is a JSR-286 (also known as Portal 2.0) compliant portal (and a whole lot more). Since I am in the market for a portal server for an upcoming project, I figured I needed to check Liferay out. The folks at Liferay have bundled version 6.2 with a number of different open-source application servers, including JBoss 7.1.1, but what fun would it be to simply download a bundle? Liferay is also available as a war download for deployment on existing (and closed-source) application servers. So let’s see if we can get Liferay running on the JBoss 7.2.0 server we built previously.
GateIn is a JSR-286 (also known as Portal 2.0) compatible portal based on the JBoss application server (soon to be known as WildFly). The latest version of GateIn with a provided build is GateIn 3.6.0 and is bundled with JBoss 7.1.1. (There is also a beta build of Red Hat JBoss Portal 6.1.0 which bundles GateIn with JBoss EAP and thus carries a more restrictive license.) Note that GateIn is bundled with the application server and is not an add-on to an existing application server.
As you may or may not be aware, a great many changes have been happening to the JBoss application server since being purchased by Red Hat. Most importantly, the application server is being rebranded as WildFly for version 8. ("Why?" is the first entry on the WildFly FAQ if you are curious.) But since WildFly is not quite ready as of this writing (but looks real close), we are going to deal with the latest community release, JBoss AS 7.2.0.
Deploying RESTful web services on JBossAS 7 is relatively painless and straightforward. Thanks to the extensive support of annotations vs configuration in JEE 6, creating RESTful web services is almost XML-free.
By the way, the RegexLinkPlugin is a nice way to map wiki text to links in your Trac installation. For example, I am using it on an IT wiki where each server has its own page but the servers are all referred to by all lowercase hostnames. Using RegexLinkPlugin I can map each hostname to link to the page for the server with no extra wiki markup, ensuring my users always generate the links when using the hostnames.
As the number of CentOS (or Red Hat) machines in your environment grows, you begin to appreciate the need for a central login mechanism. Most workplaces already have a such a login for their Windows workstations in the form of an Active Directory domain. By joining your CentOS machines to the Active Directory domain, you allow users to login with the same credentials as on their Windows machines. Furthermore you do not need to add or remove users when new people join the team or others drop off the team.
In the past I have detailed how I set up a mail server for development application servers. Today I want to explain how to set up a mail server for a production application server, or one that should interact with real-life mail systems.
Back when I was fooling around with Ruby I wrote some code using the ruby-taglib library for manipulating mp3 tags. Later, I went through the process of installing Ubuntu 12.10 from scratch on my main system. Eventually I tried running the old on the new system and discovered that I needed to re-install ruby-taglib and ran into some difficulties.
A quick example script for creating a table in an Oracle database only when it does not already exist.
I recently went through the exercise of adding an additional JBoss application server to a production CentOS 6.4 server. The two applications were to be hosted on the same machine using virtual name servers to distinguish requests. I have covered virtual name servers before in my post on install Trac on CentOS 6. Multiple instances of JBoss can be made to play nice on the same servers by shifting the ports via the switch ‑Djboss.service.binding.set=ports‑01.
Just a quick post in case someone else ever encounters this issue. I got the following error when migrating an unchanged web application to CentOS 6.3 from an earlier version of CentOS:
If you have ever needed to develop a web application you have probably needed to send email from the application. Frequently in the applications I work on, we end up using the email address as the login, which means we need lots of email addresses for unit test and integration testing, etc. Using real email addresses for this is not very convenient, so we have used a separate development mail server. Ideally this mail server will accept mail from any development machine, but will not relay mail to any real addresses (so it won’t be an open relay).
Now for the exciting conclusion of our three-part series on installing Trac on a 64-bit server running CentOS 6.3. In part 1 I installed some prerequisite software and Trac itself. In part 2, I installed and configured Apache as a front end to Trac. In part 3, I will configure Trac to use an Active Directory domain for authentication.
Recently I had the need to set up a Trac instance on a 64-bit machine running CentOS 6.3. In part 1 I installed some prerequisite software and Trac itself. In part 2, I will be installing Apache as a front end to Trac. In part 3, I will configure Trac to use an Active Directory domain for authentication.
Recently I had the need to set up a Trac instance on a 64-bit machine running CentOS 6.3. For CentOS and Red Hat 5, someone has done the hard work already and set up RPM files (see the Trac documentation on RHEL 5 and Dag Wieers RPM repository for details) making installing Trac as easy as yum install trac. Unfortunately, our benefactors have not gotten to RHEL 6 yet so I needed to do it myself.
Just a quick and dirty note to solving the following error from Subversion:
SVN: E200031: attempt to write a readonly database.
I found the answer on Tor Henning Uelands blog under the post http://h3x.no/2010/12/04/svn-gives-attempt-to-write-a-readonly-database-error. The solution was to fix the permissions on the db/rep-cache.db file in the subversion repository. See his blog if you need more details. Thanks Tor.
A few weeks ago I upgraded my HTPC to Ubuntu 12.10 and was treated to a nasty surprise: the overscan settings for the nvidia driver were no longer recognized. The HTPC is connected to my television (naturally) which is a 40" LG LCD HDTV. If you have ever tried to connect your PC to an HDTV before, you probably encountered the problem of that the visible portion of the screen is smaller than the drawable portion of the screen. The result is that the edges of the screen are not visible. In my case that meant the dash and the universal menu of Unity could not be seen. That makes for a less than usable experience.
I recently upgraded to Ubuntu 12.10 on my main desktop machine from scratch, which means a number of things which had been installed and configured need to be re-done. One of those things is my VPN connection to work, which runs Windows 2008 Server for VPN.
A big hat tip to Asaf Shahar for this one.
Recently I took the plunge and put an SSD drive into my desktop. Since I needed to re-install the OS, I figured I would install the latest Ubuntu, version 12.10. I went over my trials and tribulations of getting the OS installed in part 1, and dealt with swap in part 2. Today we finish up the tweaks for the SSD.
Recently I took the plunge and put an SSD drive into my desktop. Since I needed to re-install the OS, I figured I would install the latest Ubuntu, version 12.10. I went over my trials and tribulations of getting the OS installed in part 1, today we are going to talk about some changes I made afterwards to support the SSD.
Recently I took the plunge and put an SSD drive into my desktop. Since I needed to re-install the OS, I figured I would install the latest Ubuntu, version 12.10.
In the process of converting an application from JSF 1.2 to JSF 2.1, I came across the following structure:
So when I get the chance I am working through Bruce Tate’s Seven Languages in Seven Weeks (it might end up being seven years in my case) and commenting on it when the mood strikes. I am currently working through the exercises for Io Day 2 and today I was contemplating the final exercise.
The ANT build tool for Java does a pretty decent job of abstracting away OS concerns from your build script. E.g., file paths can always be represented using the / separator and there are tasks for all the typical file system and build operations.
As you are probably aware, I am working my way through Seven Languages in Seven Days by Bruce Tate. (And if you have ever googled basic questions on the Io language, you will know that I am not the first person to have this idea.) In any case, I am on Day of Io, but before I get to anything specific there, I wanted to share a gotcha of Io that I encountered.
I recently hit an error I had never seen before:
Recently I have been upgrading a JEE application to the latest versions of the libraries used. In particular I was upgrading from Hibernate 3 to Hibernate 4.
I finally got back to my little Ruby project over the weekend. The idea was to write a tool to copy an m3u play list and associated files to my mp3 player since Rhythmbox and Banshee were not up to the task. I used the ruby-taglib library from http://robinst.github.com/taglib-ruby/ to access mp3 tags.
So I finally got back to my Ruby play list project. The next mini-goal would be to parse a play list file and print out the converted file names. I created a PlayListEntry class and a PlayList class and things were moving along very well:
I wanted to explore Ruby a little more so I needed to give myself a project. I figured I would try to create a script to copy a playlist to my MP3 player, since both Rhythmbox and Banshee had issues with this.
My notes on the final section on Ruby from Seven Languages in Seven Days by Bruce Tate.
My notes on Day 3 of Ruby from Seven Languages in Seven Weeks by Bruce Tate follow.
I ran into a situation today where I wanted to script deletion of folders older than a set number days on an old Windows 2000 machine. (The culprit is a commercial SMTP spam and virus filter that does not clean up after itself when it updates. Eventually the drive gets full and no mail comes through.) I found a solution using forfiles but this version of Windows does not have it. I found myself searching the web and gnashing my teeth over the limitations of Windows batch scripting.