IoC : Ulises Fasoli's blog: May 2013

Managing system scoped jars with maven and the addjars plugin

When using some third party dependencies in a maven project you realize that sometimes some of jars are not available in any of the public maven repositories available (e.g. the oracle jdbc driver that is not available for copyright reasons)

When developing a team project and that you are required to use a jar of this type you have mainly 3 options :

1. Using Maven repository repository manager

There are a few maven repository managers out there which allow mainly to mirror distant maven repositories such as maven central, by storing the remote jars locally and making them available inside the company

This is where you can store your companies jars and wars and some other jar not available in the public repositories

I will not go into the details of the different repository managers but there are mainly 3

I never used Archiva but I really like Nexus. There is a nice comparison matrix over here so you can make and educated choice

Anyhow if you or your company have a repository manager you can easily install the required JAR on your repository.

Once the JAR is installed in the repository it will be available to anyone that uses the repository as long as your settings.xml file or pom.xml file are properly configured.

The main advantage if this approach is that once the JAR downloaded and installed in the repository manager it will be available for all the users and future projects

The main inconvenient is the fact that you need to install a repository manager

2. Installing the JAR in the maven local repository

Installing a JAR in the user's maven local repo is quite straightforward

a) Download the JAR to the local machine

b) Install the JAR in the local repository

    mvn install:install-file -Dfile=/data/downloads/ojdbc6.jar -DgroupId=com.oracle -DartifactId=ojdbc6 -Dversion=11.2.0.3

c) Declare the JAR as a maven dependency


   

       .....

      
          
              =com.oracle
              ojdbc6
              11.2.0.3

This is the quickest and simplest approach to implement

The major inconvenient is that every new developer will need to install the JAR in their local repository

3. Using the addjars shade plugin and system as dependency scope

Maven allows you to easily defined dependencies with a system scope. But there is a problem with system scoped jars. When packaging the application (WAR, JAR, etc.) the system scoped jars will not be included in the packaged result. Here is where the addjar plugins comes in handy, this plugin allows you to include system scoped jars when packaging the application

Below is a quick example of a simple java web app with system scoped jar (ojdbc6.jar) :

my-app
|-- pom.xml
`-- src
    |-- main
    |   `-- java
    |   `-- webapp
    |-- external
    |   `-- ojdbc6.jar

As stated before if I run a mvn package on this project I will get a WAR file but the ojdbc6.jar JAR will not be included under WEB-INF/lib

Thankfully the addjars plugins comes to the rescue here this plugin will include your third party jar in your project's classpath when packaging

You can see below a sample configuration for the plugin in the pom.xml file :


   
...

  
      
       com.googlecode.addjars-maven-plugin
       addjars-maven-plugin
       1.0.5
          
             
                
                  add-jars
                
                
                  
                    
                      ${basedir}/external/
                    
                 
              
           
        
      
    
  
...

The main advantage is that once the pom.xml configured with the dependency and the plugin and the JAR committed into the source control the building becomes transparent for the users

The main inconvenient comes from the fact that you will need to commit the JAR file in your source control repository and handle JAR versions manually

It's good to note that the add-jars plugin requires maven 3.0.3+

Reconfiguring a mongodb replicaset after a "loading local.system.replset config (LOADINGCONFIG)" error

Weird thing happen today when I came to work my MongoDB replicaset was not working anymore after a system update

There was a mongodb instance running but when I checked for the replicaset status I had this error message :

> rs.status()

{
        "startupStatus" : 1,
        "ok" : 0,
        "errmsg" : "loading local.system.replset config (LOADINGCONFIG)"
}

Now I have no idea what caused the problem but I could see (from the error message) that it was related to the replicaset configuration

The problem was actually pretty weird since when I printed the replicaset config it showed an old configuration

> rs.config()
{
        "_id" : "rps",
        "version" : 2,
        "members" : [
                {
                        "_id" : 0,
                        "host" : "192.168.13.200:27017"
                },
                {
                        "_id" : 1,
                        "host" : "192.168.13.201:27017"
                }
        ]
}

Since this is a development environment I didn't have a database backup so I really needed the replicaset to start running again

Thankfully MongoDB (since version 2.0) offers a relatively easy way to reconfigure a replicaset that is the rs.reconfig() command

In my case what I had to to was to reconfigure my replicaset with the only surviving member (itself) since the second one was under heavy maintenance.

This operation can be done in 6 steps :

1. Get the current replicaset configuration into a variable

> var cfg = rs.config()

2. Overwrite the members property with the remaining replicaset nodes


> cfg.members = [{"_id" : 3, "host"  : "192.168.1.100"}]
[ { "_id" : 3, "host" : "192.168.1.100" } ]

3. Reconfigure the replicaset with the new configuration

> rs.reconfig(cfg , {force : true})
{
        "msg" : "will try this config momentarily, try running rs.conf() again in a few seconds",
        "ok" : 1
}

4. Wait for the configuration to be applied

Give it a few seconds and run again the conf command to see if the new configuration is properly applied

> rs.conf()
{
        "_id" : "rps",
        "version" : 77682,
        "members" : [
                {
                        "_id" : 3,
                        "host" : "192.168.1.100:27017"
                }
        ]
}

5. Restart your mondod instance

/etc/init.d/mongod restart

6. Check that everything is running properly


rps:PRIMARY> rs.status()
{
        "set" : "rps",
        "date" : ISODate("2013-05-23T07:54:47Z"),
        "myState" : 1,
        "members" : [
                {
                        "_id" : 3,
                        "name" : "192.168.1.100:27017",
                        "health" : 1,
                        "state" : 1,
                        "stateStr" : "PRIMARY",
                        "uptime" : 8,
                        "optime" : {
                                "t" : 1352365425,
                                "i" : 1
                        },
                        "optimeDate" : ISODate("2012-11-08T09:03:45Z"),
                        "self" : true
                }
        ],
        "ok" : 1
}

Sources :

Reconfigure a Replica Set with Unavailable Members

JSF 2 performance improvement on latest release (Mojarra)

According to this blog the latest version of Mojarra JSF (2.1.22) performance should improve dramatically when handling pages with a large quantity of objects (1000+).

jsf-performance-mojarra-improves-dramatically

Always acording to the blog author with the previous version of Mojarra, rendering a page with 1000+ components would take up to 5 times more compared to the other JSF implementation Apache MyFaces.

This is great news and comes as a welcomed improvement!

This improvement comes mainly from the resolution of the bug :

JAVASERVERFACES-2494