OS X ethernet self-assigned ip

Recently I had a problem with my mac, my wifi connection was working properly but my ethernet connection was not it was getting a self-assigned IP. After checking the obvious culprits (cable, router, switch) it turns out that the problem was elsewhere.

After searching the internet I realized that I wasn't the only one having this problem, and there are a lot of fixes such as :

  • Deleting the "/Machintosh HD/Library/Preferences/com.apple.alf.plist" and rebooting
  • Resetting the PRAM
  • Recreating a network configuration

By chance I decided to try and disable IPv6 on the network interfaces like so :

networksetup -setv6off Wi-Fi
networksetup -setv6off Ethernet

And after rebooting it worked !!

So there you go; I hope this works for you too!!

On a final note: Another thing I was about to try was uninstalling the virtual interfaces of my VMWARE but it didn't get to that

Git svn clear stored credentials

Recently a change was made in my company in the way the SVN repositories were handled; as a result we had to change the accounts we used to access the repos

Whenever I tried pulling or pushing info into those repositories I was getting errors like :


RA layer request failed: PROPFIND request failed on '/svn/2001/ufasoli/myproject/trunk': PROPFIND of '/svn/2001/ufasoli/myproject/trunk'
: 403 Forbidden (https://internal.svn.com) at /lib/Git/SVN.pm line 717

I realized that it was because the credential information was cached locally on the machine, so the system was sending old information , the tricky part was that the old accounts allowed authentication on the repositories, they were just no longer authorized to do anything on them, so I was getting an HTTP 403 error and the system was not prompting me for a new password (since the old accounts could still log in...)

So this is how I fixed it on my windows machine:

Under your user folder you should have a folder where subversion stores cached data C:\Users\ulf\.subversion (in my case)

This folder contains an auth folder were you will normally find another 3 folders :

  • svn.simple
  • svn.ssl.server
  • svn.username

To delete the cached credentials you can delete the content of the following folders :

  • svn.simple
  • svn.ssl.server

Once this folders deleted git should prompt you again for your username/password

Building and installing git 2.x on Windows

So Git 2.x has been out for a few months now and it came with some nice stuff, you can read more about it here

However if you are under windows, the git portage msysgit has yet to release a 2.X portage(as of this writing the latest version is 1.9.4)

If you want to install Git 2 on Windows you will need to build it from the source, and here is how it's done

1. Download the Git build environment

Head up to the Github page https://github.com/msysgit/msysgit and download the latest version from the master branch

Unzip it let's say to c:/tmp/git/msygit-env

2. Download the latest version of git

Head up to the Github page https://github.com/msysgit/git and download the latest version from the master branch

Unzip it let's say to c:/tmp/git/git

3. Copy the git folder

Now copy the entire contents of the c:/tmp/git/git under c:/tmp/git/msygit-env/git

4. Build Git

Now you can fire up a DOS console and head up to the msysgit and build Git


cd c:/tmp/git/msygit-env
msys.bat

Once the build starts you should see some output similar to

-------------------------------------------------------
Building and Installing Git
-------------------------------------------------------
GIT_VERSION = 2.1.0
    * new build flags
    CC credential-store.o
    * new link flags
    CC abspath.o
    CC advice.o
    CC alias.o
    CC alloc.o
    CC archive.o
    CC archive-tar.o

5. Moving the binaries and updating the path

Once the build is finished you will find the git binaires under the /bin folder

So let's say for example that I want to put my git binaries under c:/dev/bin/git2 go ahead and copy the following folders from the c:/tmp/git/msygit-env/git :

  • bin
  • cmd
  • etc
  • include
  • lib
  • libexec
  • mingw
  • share
  • ssl

Please note that I don't think you actually need all those folders but I copied them all just to be sure ..

Now for the final step the PATH; you will need to add the following folders to your PATH :

$PATH;C:\dev\bin\git2\bin;C:\dev\bin\git2\mingw\bin;C:\dev\bin\git2\cmd

Once the cmd prompt restarted you should be able to use your newly build Git

git --version
git version 2.1.0

And there you go if everything went as expected you should be running git 2.x

NodeJS, tune or disable HTTP agent pooling

When using NodeJS's HTTP module to query you might end-up having performance problems if you do some heavy HTTP querying.

By default when executing queries using the HTTP module NodeJS will use connection pooling with the maximum number of connection sockets being 5, so if you hit the bottleneck your HTTP queries will lag as they will be queued.

To my knowledge you have 2 options to "counter" this behavior :

  1. Increase the number of http sockets
  2. Disable the HTTP agent per request

1. Increase the number of http sockets

    var http = require('http');

    // increase the maximum number of http connections in the pool
    http.globalAgent.maxSockets = 100;

    //regular http request options
    var options = {
        port: 1337,
        hostname: '127.0.0.1',
        method: 'GET',
        path: '/test'
  };

  // make http query
  var req = http.request(options, function(res) {
       console.log('STATUS: ' + res.statusCode);
       console.log('HEADERS: ' + JSON.stringify(res.headers));
       res.setEncoding('utf8');
       res.on('data', function (chunk) {
          console.log('BODY: ' + chunk);
      });
   });



2.Disable the HTTP agent per request


    var http = require('http');
  
      //regular http request options
      var options = {
         port: 1337,
         hostname: '127.0.0.1',
         method: 'GET',
         path: '/test',
         agent:false //disable the nodejs agent (no connection pooling)
      };

      // make http query
      var req = http.request(options, function(res) {
       console.log('STATUS: ' + res.statusCode);
       console.log('HEADERS: ' + JSON.stringify(res.headers));
       res.setEncoding('utf8');
       res.on('data', function (chunk) {
          console.log('BODY: ' + chunk);
      });
   });

Please be aware that changing this options might have side effects on your host system such as higher memory and bandwidth use so use it wisely

Spring boot JPA broken encoding on database when loaded from data.sql file

As covered in a previous article (here and here) spring-boot is a very useful framework when working on full enabled Spring projects

Recently I wasted some time with yet another encoding problem.. where all my accentuated and special characters where corrupted.

I was using the data.sql convention that states that if a file named data.sql is found in the CLASSPATH spring will use this file to bootstrap the database, my SQL file was properly encoded in UTF-8 as well as my maven-resources-plugin however the data recovered from the database was corrupted (accents and special characters where broken)

After reading a bit the documentation I found out that the source of the problem was at the moment of reading the SQL file that the encoding was causing trouble.. thankfully you can fix this one pretty easlily by changing one property value :

spring.datasource.sqlScriptEncoding=UTF-8

spring-boot has a lot of useful properties that allow you to tune the framework which you can find here

Maven custom packaging with the assembly plugin

It's not uncommon to need a custom packaging or assembly for a given project for some reason or another, this can be accomplished in a certain number of ways

Recently I needed an application to be packaged as the following structure :

|- runnable-jar.jar
|- lib
    |-- axis.jar
    |-- commons.logging.jar 
|- certificates
   |-- cacerts.jks
|- config
   |-- config.properties
|- logs
   

The schema is pretty self-explanatory I needed a runnable JAR at the root of my dist folder with a few other folders such as config, logs, etc.

One way to accomplish this with maven is to use maven-assembly-plugin

The Assembly Plugin for Maven is primarily intended to allow users to aggregate the project output along with its dependencies, modules, site documentation, and other files into a single distributable archive.

Your project can build distribution assemblies easily, using one of the convenient, prefabricated assembly descriptors.

These descriptors handle many common operations, such as packaging a project's artifact along with generated documentation into a single ZIP archive. Alternatively, your project can provide its own descriptor and assume a much higher level of control over how dependencies, modules, file-sets, and individual files are packaged in the assembly.

Currently the plugin can create distributions in the following formats:

  • zip
  • tar
  • tar.gz
  • tar.bz2
  • jar
  • dir
  • war
  • format that the ArchiveManager has been configured

For this tutorial we will be using the dir format in order to output the project structure described above

Let's start with the easy part first, the maven assembly plugin configuration where we will tell the plugin where to find our assembly file and where to output the result of the assembly operation


    
...

    
        
            
                maven-assembly-plugin
                
                    false
                    
                        
                        src/main/resources/assembly.xml
                    
                    
                    ${project.build.directory}/dist/
                
            

            
                maven-resources-plugin
                
                    UTF-8
                
            
            
                maven-compiler-plugin
                
                    ${java.version}
                    ${java.version}
                    ${project.build.sourceEncoding}
                
            
        
    
...


Now since in our case we want all the files in the resource directory to be handled by the assembly plugin we will configure the maven resources plugin to ignore everything inside the resources folder (please note that this is an optional step and it might not apply to your project)


...  

    
       
          ${basedir}/src/main/resources
          
              **/**
           
        
     

...

Once the maven part is done we can get started with the core code

If you remember we will end up with a runnable JAR file so go ahead and create a Main class like so :


package com.ufasoli.maven.custom.assembly;

/**
 * User: Ulises Fasoli
 * Date: 23.06.2014
 * Time: 18:03
 * Project : maven-custom-assembly
 */
public class Main {

    public static void main(String[] args) {
        System.out.println("HELLO WORLD !");
    }
}

Since this is going to be a runnable JAR file we will need to configure the maven JAR plugin to generate the manifest file with our main class




   org.apache.maven.plugins
   maven-jar-plugin
   2.4
   
      
         
            com.ufasoli.maven.custom.assembly.Main
            lib/
            true
         
       
   

Now we get to the core of the subject, the assembly file :


    paynet-dir
    
        dir
    
    false
    
        
        
            /lib
            
                ${project.groupId}:${project.artifactId}
            

        
             
            
                /
                
                    ${project.groupId}:${project.artifactId}
                
            

    

    
        
            src/main/resources/keystore/Certificate.SSL
            /certificates
        
        
            src/main/resources/config
            /config
        

        
            src/main/resources/config
            /logs
            
                *
            
            false
        

        
            src/main/resources/docs
            /docs
            
                *
            
        
    

Now this file is pretty self-explanatory but below are the highlights :

  • format --> the output format for our assembly (directory in our case)
  • dependencySets--> which artifacts to include in the final structure and where to put them
  • fileSets--> which files to include in the final structure and where to put them

Now you can build your assembly by running the following maven goal :

    mvn clean package assembly:single

Once the goal completed under the /target folder you should find your custom project structure

As usual you can find the code source for this tutorial over at my github account here

Asciidoctor maven integration : introduction to asciidoctor and maven asciidoctor plugin part 2/2

This is the second part of the Asciidoctor maven integration tutorial part 1/2 where we explore some of Asciidoctor cool features

4. Additional cool formatting elements and content

There are plenty of nice cheat-sheets out there that resume much better all the cool stuff you can do with (see 5. Some useful links) so I will just list here a few tips to get you started

4a. Asciidoc files inclusion or composition

Personally when writing documentation I like to create a separate file for each topic and then include them in an a big index file (you can do this otherwise if you prefer) this can easily be done using the include macro

Let's create a new Asciidoc page named topic1 and add some content to it

= Topic 1

== Intro

This page describes some information related to topic1

and now include the newly created page using the include macro

= Asciidoctor hello world



include::topic1.ad[]

After re-compiling the code you should end up with the content of the file topic1.ad inside the index.html file

4b. Table of contents (TOC)

Asciidoctor has a lot of macros and attributes that help you when writing documentation, the full list of attributes can be found here

Attributes are configured as child tags of the attributes XML tag under the maven asciidoctor plugin. To enable the table of contents while providing a TOC level we will use the toclevels attribute, since once you start writing a lot of documentation you could end up with a pretty big HTML document it's a good idea to enable the creation of anchors using the setanchors attribute



  
     
          org.asciidoctor
          asciidoctor-maven-plugin
          ${version.asciidoctor}
          
              
                 output-html
                 generate-resources
                 
                     process-asciidoc
                 
                 
                     html
                     book                    
                     
                          
                          true
                          
                          3
                     
                 

               
           
      
  


Once you configured the maven plugin it's time to add the :toc: attribute to the index.ad header

Please be aware within the the first lines of a document known as document header spacing and markup are important as they have special meaning and are handled differently by the asciidoc parsing engine

, for more information on the document header please check the documentation here

= Asciidoctor hello world
:toc:


include::topic1.ad[]

Once the documentation files generated the result should be pretty close to the one in the picture below :

Please note : Not all attributes are supported through the maven asciidoctor plugin so you have to play a bit with the maven configuration to see which ones are supported.
4c. Adding images in your documentation

Everyone knows a picture is worth 1000 words so why don't add some pretty pictures to your documentation

By default when generating the documentation files containing images the asciidoctor plugin will prefix all image paths with images/ this of course can be changed but I usually leave it with the default option

We will now add an images folder to our maven project under src/main/resources/images and put an image of your choice inside of it in my case asciidoc-logo.png

Once this is done let's add our image to our document

= Topic 1

== Intro

This page describes some information related to topic1.

Asciidoc is cool

image::asciidoc-logo.png[Asciidoc logo]

Now we have included an image in our doc file but we're not done yet, you need to instruct maven to copy our images folder to the generated-docs target folder

 
...
        
            
                
                src/main/resources/images
                ${build.directory}/generated-docs/images
            
  .....


4d. Code syntax highlighting

Code syntax highlighting is very important when writing documentation since it helps with the readability. Asciidoc currently supports 4 frameworks to handle your code highlighting

  • coderay
  • prettify
  • highlightjs
  • pygments (not currently supported by maven asciidoctor plugin)

For this tutorial let's say we will use coderay so we first need to activate the syntax highlighting in the maven POM file :



  
      
          org.asciidoctor
          asciidoctor-maven-plugin
          ${version.asciidoctor}
          
             
                 output-html
                 generate-resources
                 
                    process-asciidoc
                 
                 
                      
                      coderay
                      html
                      book

                      
                         
                         true
                         3
                     

                 
              
          
       
    
  

Once our maven configuration is done we can add some source code to our docs, the syntax is pretty straightforward in it's most basic form you just put [source, language] and you surround your code with ---- like so :

[source,java]
----
public class HelloWorld{

   public static void main(String[] args){
      System.out.println("Hello World");
   }
}
----

Once your docs file regenerated you should see something like this :

4e. External links (target _blank)

Whenever I'm reading an HTML documentation containing a link I prefer it when the link opens automatically in a new tab i.e.target="_blank"

This can be achieved using link attributes however by default in Asciidoc this feature is disabled; luckily you just need one small line in your pom.xml file to enable this feature with an attribute


  
      
          org.asciidoctor
          asciidoctor-maven-plugin
          ${version.asciidoctor}
          
             
                 output-html
                 generate-resources
                 
                    process-asciidoc
                 
                 
                      
                      coderay
                      html
                      book

                      
                         
                         true
                         3
                         
                        true
                     

                 
              
          
       
    
  

Now you can go ahead an add your links withe


http://powerman.name/doc/asciidoc[Asciidoc cheatsheet, window="_blank"]


So this concludes this 2 part introductory tutorial to Asciidoctor and maven integration ; have fun writing cool documentation!

5. Some useful links

As usual you can find the code source for this tutorial over github here

Below is a list of useful links to help you with Asciidoctor such as cheatsheet or general documentation :

Asciidoctor maven integration : introduction to asciidoctor and integration with maven asciidoctor plugin part 1/2

For some time now I have been hearing a lot aboutAsciiDoc as a mean to write documentation but never had the chance to use it...

Recently I stumbled upon AsciiDoctor and since I was about to begin working on a small project with no previous documentation I thought it was the perfect time to try it out..

Documentation is an important part of a project which more often than we would like gets put aside for a great number of reasons. One of them is that we as developpers tend not to like writing documentation...

0.Intro and scope

In this tutorial I will show you how to integrate Asciidoctor class in your Java project and get you started with a small documentation example as well as some tips such as :

  • Asciidoc templating using fragments
  • Generating a TOC (table of contents) for your documentation
  • Integrating images in your asciidoc files
  • Code syntax highlighting in your asciidoc files
  • Making external links (i.e. _target blank)

Please note that I assume you have some knowledge of Asciidoc so I won't delve into much detail regarding Asciidoc

1. What is AsciiDoc ?

AsciiDoc is a text document format for writing notes, documentation, articles, books, ebooks, slideshows, web pages, man pages and blogs. AsciiDoc files can be translated to many formats including HTML, PDF, EPUB, man page. AsciiDoc is highly configurable: both the AsciiDoc source file syntax and the backend output markups (which can be almost any type of SGML/XML markup) can be customized and extended by the user.

2. What is Asciidoctor ?

Asciidoctor is a pure Ruby processor for converting AsciiDoc source files and strings into HTML 5, DocBook 4.5 and other formats. It’s published as a RubyGem and is available under the MIT open source license.

I invite you to take a look to this nice presentation by Dan Allen Discover Zen Writing with Asciidoc which gives you a good overview of AsciiDoc

3. First steps and configuration

First things first go ahead and create a simple maven module let's say a simple JAR for example using the maven archetype plugin or using you favorite IDE

mvn archetype:generate -DgroupId=com.ufasoli -DartifactId=asciidoc-helloworld -DinteractiveMode=false

Once your maven project is created go ahead and create a folder named asciidoc under src/main this is where we will be putting our Asciidoc files

Let's go ahead and create our first asciidoc file under the folder we just created let's name it index.ad and for the moment keep it simple let's just add the page title

= Asciidoctor hello world

So now with our first asciidoc file let's go ahead and configure maven to parse our documentation files and generate HTML documentation files by using the Maven Asciidoctor plugin




  
     
          org.asciidoctor
          asciidoctor-maven-plugin
          ${version.asciidoctor}
          
              
                 output-html
                 generate-resources
                 
                     process-asciidoc
                 
                 
                     html
                     book                    
                 
               
           
      
  

Now if you run a mvn clean compile you will see an index.html that will be generated under the target/generated-docs folder with an output similar to :

So that's it for the first part of this tutorial, you can find the rest tomorrow on part 2

Java Mail network is unreacheable connect exception

Recently I stumbled upon a weird problem while debugging a simple java application that needed to send an email

Since I was debbuging this application locally I used the FakeSMTP tool that I described in this tutorial here : Testing email sending functionality with FakeSMTP which I run locally on my machine

So after editing the configuration on my Java program and firing up the SMTP server I was quite surprised to get the following exception :

Caused by: javax.mail.MessagingException: Could not connect to SMTP host: 127.0.0.1, port: 25 (java.net.SocketException: Network is unreachable: connect)
System.setProperty("java.net.preferIPv4Stack" , "true");

So once you are sure you problem is not coming from a non running SMTP server or a network connection, you can check if the culprit is no other than Java

If you read the Oracle documentation here you will see that by default Java prefers IPv6 to IPv4 which is the problem in our case since FakeSMTP binds on IPv4

Luckily there is a way to force Java to prefer IPv4 over IPv6 using the system property java.net.preferIPv4Stack

This can either be done :

  • programmatically
  • using java options

1. Programmatically


 System.setProperty("java.net.preferIPv4Stack" , "true");

2. Using java options


java -jar myJar.jar -Djava.net.preferIPv4Stack=true

That should take care of the problem

Another solution would be to disable IPv6 networking on your machine but that may have other side effects on your system..

Heroku PostgreSQL and DBVisualiser connection using SSL

I occasionally use Heroku to deploy webapps on the cloud combined with a Postgres database to store my relational data

I recently found a multi-platform polyglot SQL client that I could use with my MAC, this product is called DbVisualiser

However since Heroku requires an SSL security on external connections after providing the usual database connection properties (url, username, password) when I tried to connect through DbVisualiser I was getting the error message :

FATAL: no pg_hba.conf entry for host "86.200.9.63", user "u4b1uljsil33m2", database "de9td8cv06p4se", SSL off

After playing a bit with the different options and reading the Postgres JDBC driver over here I found out that you can provide an Non Validating SSL factory in the connection properties to satisfy Heroku's SSL requirements

In order to configure the SSL properties in DbVisualiser you need to edit the following SSL properties in the Properties tab :

  • SSL : true
  • sslfactory : org.postgresql.ssl.NonValidatingFactory

By providing these 2 properties you should be able to connect to your Heroku database without any problems

SSH linux how to kill an idle or innactive connection

Sometimes when you're disconnected abruptly from a remote server like if your network connection gets dropped, you can be left with a ghost or inactive SSH session.

This can become pretty annoying when you're doing some SSH port redirection since you will not be able to bind to a given port since the ghost connection is still using that port, and you might end up with error messages such as the following :

debug1: Local connections to LOCALHOST:21521 forwarded to remote address localhost:21521
debug1: Local forwarding listening on 127.0.0.1 port 21521.
bind: Address already in use
debug1: Local forwarding listen

Now there are a few ways of dealing with this issue, the one I prefer is a 3 step operation :

1.Check who is connected to the server

This step is actually optional but it allows you to check which user is currently connected to the server and prevent accidentally destroying another user's session (or at least warning him that you will do it ;) )

To check who's connected to the server you can run the w command. the w command shows who is logged in to the system and what they are doing.

So go ahead and run the following command on your prompt :

   [ufasoli]> w

You should see an output similar to this one

 20:16:14 up 132 days,  3:38,  2 users,  load average: 0.04, 0.03, 0.00
USER     TTY        LOGIN@   IDLE   JCPU   PCPU WHAT
root     pts/0     20:07    0.00s  0.02s  0.00s w
root     pts/1     20:09    6:17   0.02s  0.02s -bash

Here you can identify your user with the WHAT column as it indicates what the user is doing (invoking the command w in our case) /

2.Display the running processes

By using the pstree command with the -p to show process identification numbers (PIDs)

Go ahead and run the following command :

[ufasoli]> pstree -p

pstree displays the processes (i.e., executing instances of programs) on the system in the form of a tree diagram so when running the above command you should have an output similar to the one below :

init(1)─┬─cron(8865)
        ├─cupsd(2385)
        ├─oracle(2063)
        ├─oracle(2065)
        ├─oracle(2067)
        ├─oracle(2069)
        ├─oracle(2176)
        ├─oracle(2180)
        ├─oracle(12830)
        ├─scsi_eh_1(226)
        ├─scsi_eh_2(232)
        ├─scsi_eh_3(236)
        ├─slpd(2136)
        ├─sshd(2411)─┬─sshd(12840)───bash(12842)───pstree(12908)
        │            └─sshd(12887)───bash(12889)
        ├─sshd(14276)
        ├─syslogd(2035)
        └─tnslsnr(3917)


3.Kill the unwanted process

In our case the unwanted session has the PID 12287 as it's the session without the pstree command that we've just issued.

You can now kill the unwanted PID (just be careful not to kill a colleagues session ;) ):

   [ufasoli]> kill -1 12887

Once the session is killed you should be able to bind to the previously occupied port

Running a spring boot application with maven

On the last 2 part tutorial that I published recently on Spring boot :Spring boot and spring data (part 1) and Spring boot and spring data (part 2) I said that when using pure maven (not the groovy approach) you needed to either package the project and then run the JAR manually or use the maven mojo exec plugin (which I preferred)

But as often after playing a bit more with it I realized that there is an even simpler solution and that is using the run goal of the spring-boot maven plugin

So you can simply run your spring-boot project by executing the following goal on your console/IDE


 mvn spring-boot:run

Spring boot and spring data jpa tutorial - A sample application using spring 4.0 spring boot and JPA (part 2/2)

This is the second part of the Spring boot and spring data jpa tutorial - A sample application using spring 4.0 spring boot and JPA

At the end of the tutorial I promised you that we will be removing one of the steps when running the application, that is merge the package and run in a maven command and make him do the work

5.- Making maven run the JAR directly

We're going to make maven run the runnable JAR for us after it has been packaged, for this purpose we're going to use one of org.codehaus.mojo maven plugins



....

        
            
                org.springframework.boot
                spring-boot-maven-plugin
            

            
                org.codehaus.mojo
                exec-maven-plugin
                1.2.1
                
                    com.ufasoli.tutorials.spring.boot.HelloWorldApp
                
            
        
    
...

So what's happening here ? :

  • By adding the exec plugin to the build section of our pom.xml and providing a mainClass when we run the appropriate maven goals the application will be packaged and run directly from maven

You can try this by running :

    mvn clean package exec:java

By running this on your console the application will be packaged and run directly using maven

Now let's add some more interesting stuff to our app

6.- Adding Spring Data and JPA support

We're now going to add some Spring Data and JPA support to our app.

The first thing you need to do is add the additional spring boot starter module (spring-boot-starter-data-jpa) to your maven dependencies and since we will be using an embedded HSQL database the dependency for the HSQL driver too:

 
 ...
        
        
            org.springframework.boot
            spring-boot-starter-data-jpa
        

         
            hsqldb
            hsqldb
            ${version.hsqldb}
        
...


The next thing you need to do is tell spring to enable Spring Data and its repository features this is done by simply adding the @EnableJpaRepositories to your Spring App class

@ComponentScan 
@EnableAutoConfiguration
@EnableJpaRepositories
public class HelloWorldApp {

    public static void main(String[] args) throws Exception {

        SpringApplication.run(HelloWorldApp.class, args);

    }
}

And that's it if you now build and run your application you will have a Spring web application with Spring Data and JPA support even though the app won't do much for the moment ;).

So what's happening here?

  • Annotating the Spring Application class with the @EnableJpaRepositories will cause a lot of "magic" to happen and a lot of things will be configured/initialized for you such as an Entity Manager, DataSource (see next item), JPA Vendor adapter ..
  • Since we haven't defined a DataSource if Spring finds an in memory JDBC driver in the Classpath it will automatically create one for us using a set of predefined conventions

Now let's add some logic to our app :

7.- Adding some Spring data and JPA logic

The first thing we're going to be doing is adding a simple JPA entity to perform some CRUD operations later on



import javax.persistence.Entity;
import javax.persistence.Id;

@Entity
public class Book {


    @Id
    protected String isbn;
    protected String title;
    protected String author;
    protected String description;
    // omitting setters/getters/constructors
}

So now that we have our entity lets use one of the great features of Spring Data : The Repositories Abstraction :

The goal of Spring Data repository abstraction is to significantly reduce the amount of boilerplate code required to implement data access layers for various persistence stores.

By annotating an interface with @Repository and making this interface extend CrudRepositoryYou will get among other things 2 pretty nifty goodies of the box:

  • Some utility CRUD methods such as findAll() or count()
  • Auto-implementation of methods based on naming convention such as findBooksByAuthor()

And the best part is you get all of this without writing any code logic for these methods (of course you can override these methods, and write some custom methods) as shown in the doc, you can even avoid yet to write some code by using for example the @Query annotation

So now lets create our CRUD repository for our entity with a custom method to find the books by their author


import com.ufasoli.tutorials.spring.boot.model.Book;
import org.springframework.data.repository.CrudRepository;
import org.springframework.data.repository.query.Param;
import org.springframework.stereotype.Repository;


@Repository
public interface BookRepository extends CrudRepository {

    public Iterable findBooksByAuthor(@Param("author") String author);
}

This interface will be picked up by Spring an instantiated accordingly.

We're almost done with our JPA/database logic, one last thing I would like to do is to have some data inserted automatically into the database when the application starts (especially since we're dealing with an in-memory database

Once again we can take advantage of another Spring convention, if you place a data.sql file in your maven resources directory the script will be automatically executed when the database will be bootstrapped and after reverse engineering your entities into the database

INSERT INTO book(isbn, title, author,description) VALUES ('1111111', 'The Spirit Thief (The Legend of Eli Monpress #1)', 'Rachel Aaron',
                         'Eli Monpress is talented. He''s charming. And he''s a thief.But not just any thief. He''s the greatest thief of the age - and he''s also a wizard. And with the help of his partners - a swordsman with the most powerful magic sword in the world but no magical ability of his own, and a demonseed who can step through shadows and punch through walls - he''s going to put his plan into effect.The first step is to increase the size of the bounty on his head, so he''ll need to steal some big things. But he''ll start small for now. He''ll just steal something that no one will miss - at least for a while. Like a king');

INSERT INTO book(isbn, title, author,description) VALUES ('2222222', 'The Spirit Rebellion (The Legend of Eli Monpress, #2)', 'Rachel Aaron',
                         'Eli Monpress is brilliant. He''s incorrigible. And he''s a thief.He''s also still at large, which drives Miranda Lyonette crazy. While she''s been kicked out of the Spirit Court, Eli''s had plenty of time to plan his next adventure. But now the tables have turned, because Miranda has a new job -- and an opportunity to capture a certain thief. Things are about to get exciting for Eli. He''s picked a winner for his newest heist. His target: the Duke of Gaol''s famous ''thief-proof'' citadel. Eli knows Gaol is a trap, but what''s life without challenges? Except the Duke is one of the wealthiest men in the world, a wizard who rules his duchy with an iron fist, and an obsessive perfectionist with only one hobby: Eli. It seems that everyone is hunting for Eli Monpress');

INSERT INTO book(isbn, title, author,description) VALUES ('3333333', 'The Spirit Eater (The Legend of Eli Monpress, #3)', 'Rachel Aaron',
                         'With the pressure on after his success in Gaol, Eli Monpress, professional thief and degenerate, decides it''s time to lie low for a bit. Taking up residence in a tiny seaside village, Eli and his companions seize the chance for some fun and relaxation. Nico, however, is finding it a bit hard. Plagued by a demon''s voice in her head and feeling powerless, she only sees herself as a burden. Everyone''s holiday comes to an untimely close, though, when Pele arrives to beg Eli''s help for finding her missing father. But there are larger plans afoot than even Eli can see, and the real danger, and the solution, may lie with one of his own and her forgotten past. If only Nico could remember whose side she''s on.');

INSERT INTO book(isbn, title, author,description) VALUES ('4444444', 'The Spirit War (The Legend of Eli Monpress, #4)', 'Rachel Aaron',
                         'Eli Monpress is vain. He''s cocky. And he''s a thief. But he''s a thief who has just seen his bounty topped and he''s not happy about it. The bounty topper, as it turns out, is his best friend, bodyguard, and master swordsman, Josef. Who has been keeping secrets from Eli. Apparently, he''s the only prince of a rather feisty country and his mother (a formidable queen who''s every bit as driven and stubborn as he is) wants him to come home and do his duty, which means throwing over personal ambitions like proving he''s the greatest swordsman who ever lived. Family drama aside, Eli and Josef have their hands full. The Spirit Court has been usurped by the Council of Thrones and someone calling herself the Immortal Empress is staging a massive invasion. But it''s not just politics --- the Immortal Empress has a specific target in mind: Eli Monpress, the greatest thief in the world.');

INSERT INTO book(isbn, title, author,description) VALUES ('5555555', 'Spirit''s End (The Legend of Eli Monpress #5)', 'Rachel Aaron',
                         'First rule of thievery: don''t be a hero. When Eli broke the rules and saved the Council Kingdoms, he thought he knew the price, but resuming his place as the Shepherdess''s favorite isn''t as simple as bowing his head. Now that she has her darling back, Benehime is setting in motion a plan that could destroy everything she was created to protect, and even Eli''s charm might not be enough to stop her. But Eli Monpress always has a plan, and with disaster rapidly approaching, he''s pulling in every favor he can think of to make it work, including the grudging help of the Spirit Court''s new Rector, Miranda Lyonette. But with the world in panic, the demon stirring, and the Lord of Storms back on the hunt, it''s going to take more than luck and charm to pull Eli through this time. He''s going to have to break a few more rules and work with some old enemies if he''s going to survive');

8.- Wrapping things up with a REST controller

To wrap things up we'll add a simple RestController that will interact with our freshly created Repository


import com.ufasoli.tutorials.spring.boot.model.Book;
import com.ufasoli.tutorials.spring.boot.repositories.BookRepository;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.http.MediaType;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RestController;

@RestController // assumes @ResponseBody annotation in methods annotated with  @RequestMapping
@RequestMapping(value = "/books", produces = MediaType.APPLICATION_JSON_VALUE)
public class BookController {

    @Autowired
    protected BookRepository bookRepository;

    @RequestMapping
    public Iterable books() {
        return bookRepository.findAll(); // uses the findAll() method inherited from CrudRepository
    }


    @RequestMapping(value = "/{isbn}")
    public Book book(@PathVariable("isbn") String isbn) {
        return bookRepository.findOne(isbn);// uses the findOne() method inherited from CrudRepository
    }


    @RequestMapping(value = "/{isbn}", method = RequestMethod.DELETE)
    public String deleteBook(@PathVariable("isbn") String isbn) {

        try {
            bookRepository.delete(isbn);
            return String.format("Book [%s] successfully deleted", isbn);// uses the delete() method inherited from CrudRepository
        } catch (Exception e) {
            return String.format("A problem occurred when deleting Book [%s]", e.getMessage());
        }
    }

    @RequestMapping("/author/{author}")
    public Iterable booksByAuthor(@PathVariable("author") String author) {

        return bookRepository.findBooksByAuthor(author);// uses the custom method defined in our BookRepository interface
    }


}

So that's it you can re-run your application now using the maven goal

     mvn clean package exec:java

You should see your application bootstrapping your database and inserting data, and once it's fully started you should be able to play with your Web Service

9.-Some final thoughts

I must say that I quite enjoyed playing with Spring boot, as long as you're using the full spring stack it helps you get things running quickly and has some very useful starter modules and conventions

I also added the actuator module which gives you some metrics and stats (as REST endpoints) on your application which is pretty cool to have when running the app in production

Check it out here

As usual you can find the code source for this application over at my github account here

Spring boot and spring data jpa tutorial - A sample application using spring 4.0 spring boot and JPA (part 1/2)

Spring boot is a strongly opinionated framework / generator based on the principle of convention over configuration, which according to the website:

Spring Boot makes it easy to create Spring-powered, production-grade applications and services with absolute minimum fuss. It takes an opinionated view of the Spring platform so that new and existing users can quickly get to the bits they need

Basically by using a few annotations and minimum boilerplate code the framework/generator will configure all the necessary beans and contexts based on a set of conventions.

Spring boot has a few modules that depending on your needs can speed-up development such as :

  • spring data jpa
  • spring data mongodb
  • spring web
  • spring actuator
  • ...

Personally I find that when using the spring stack this tool is pretty awesome!!

When using this tool you must know that there are actually 2 ways to use spring boot :

  1. Using the cli (and by extension groovy)
  2. Using good old maven and the spring-boot plugins

In this tutorial we will be building a simple Hello World tutorial as a RESTful web service

1.- Getting things started

Add the required maven dependencies to your pom.xml

        spring-boot-hello-world-ws
    spring-boot-hello-world-ws
    1.0-SNAPSHOT


    
    
        org.springframework.boot
        spring-boot-starter-parent
        1.0.0.RC1
    

    
    
        
            org.springframework.boot
            spring-boot-starter-web
        

    

    
    
        
            
                org.springframework.boot
                spring-boot-maven-plugin
            

        
    

    
    
    
        
            spring-snapshots
            http://repo.spring.io/snapshot
            
                true
            
        
        
            spring-milestones
            http://repo.spring.io/milestone
            
                true
            
        
    
    
        
            spring-snapshots
            http://repo.spring.io/snapshot
        
        
            spring-milestones
            http://repo.spring.io/milestone
        
    

So what's happening here :

  • Since spring-boot is not G.A. yet you will need to include the Spring milestones repositories
  • When using maven your project will have to inherit from the spring boot starter parent in order for it to work
  • We are using the web module (see dependencies)
  • The spring-boot-maven-plugin will build a runnable jar file

2.- Creating our first controller

With the basic configuration out of the way we can start building our app.

Since this is going to be a RESTful API we will create a REST controller. Spring included a new annotation in the latest version @RestController. Types that carry this annotation are treated as controllers where @RequestMapping methods assume @ResponseBody semantics by default; which in our case it's what we want.

So with that being said let's write our first controller :


package com.ufasoli.tutorials.spring.boot.web.controllers;

import org.springframework.http.MediaType;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

/**
 * Created with IntelliJ IDEA.
 * User: Ulises Fasoli
 * Date: 04.02.14
 * Time: 15:33
 */
@RestController
@RequestMapping(value = "/hello", produces = MediaType.APPLICATION_JSON_VALUE)
public class HelloWorldController {

    @RequestMapping
    public String sayHello(){
        return "Hello World";
    }
}

Nothing special here just a simple Spring MVC controller but using the new @RestController annotation

We are now 2 steps away from running our Spring app.

3.- Creating our Spring Application main class

In order for the Spring context to be bootstrapped you will need to create a class that will run the Spring application inside a main method and a few annotations.So let's go ahead and do that :

package com.ufasoli.tutorials.spring.boot;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
import org.springframework.context.annotation.ComponentScan;

/**
 * Created with IntelliJ IDEA.
 * User: Ulises Fasoli
 * Date: 04.02.14
 * Time: 11:39
 *
 */
@ComponentScan // spring standard component scan
// spring boot autoconfiguration will bootstrap your Spring
//application while attempting to configure the beans you need
// it will also bootstrap an in-memory database if a driver is found
// in the classpath and no datasource is defined
@EnableAutoConfiguration
public class HelloWorldApp {

    public static void main(String[] args) throws Exception {

        SpringApplication.run(HelloWorldApp.class, args);

    }
}


What's happening here? :

  • The @Component is standard spring annotation to search for annotated beans in the classpath
  • The @EnableAutoConfiguration is spring boot specific and will be doing most of the "magic"

We are now one step away from running our spring application! Yep that's it no web.xml configuration, no XML files, nothing!!

4.- Taking it for a spin

With the application configured it's time to test our app, so fire-up your IDE or your console and execute the following maven goal :

  mvn clean package

Once your app is packaged you can run the generated runnable JAR file by simple going into the target folder and running :


  java -jar .\spring-boot-hello-world-ws-1.0-SNAPSHOT.jar
 

If everything worked as expected you should see the Spring boot / maven output in your console :


  .   ____          _            __ _ _
 /\\ / ___'_ __ _ _(_)_ __  __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
 \\/  ___)| |_)| | | | | || (_| |  ) ) ) )
  '  |____| .__|_| |_|_| |_\__, | / / / /
 =========|_|==============|___/=/_/_/_/
 :: Spring Boot ::            (v1.0.0.RC1)

2014-02-04 15:46:47.628  INFO 12516 --- [           main] c.u.tutorials.spring.b
oot.HelloWorldApp  : Starting HelloWorldApp on LTULF01 with PID 12516 (C:\dev\wo
rkspaces\idea\java-blog-tutorials\spring-boot-hello-world-ws\target\spring-boot-
hello-world-ws-1.0-SNAPSHOT.jar started by ULF)
....

That's it you can now test your controller by calling the url :

 curl http://localhost:8080/hello.json

You should see the Hello world message printed out in the console

Personally it kind of bugs me to have to package the app and then run it manually so on part 2 of this tutorial we will change this so Maven will do the work for us.....

SyntaxHighlighter and blogger dynamic templates

Recently I decided to switch my blogger template to use one of Google's dynamic templates since I really like the possibility to switch the presentation of the blog posts

Even though I thought this would be pretty straight-forward as it turns out I run into a problem. I use Alex Gorbatche's SyntaxHighlighter JavaScript plugin to "prettify" my code, and as it turns out Dynamic Templates and the Syntax Highlighter do not play well together (apparently the content of the posts is loaded after the script has been bootstrapped so you end up with ugly unreadable bits of code.

After goggling here and there I found a few workarounds some worked, others not.. (I'm sorry I do not have the links now, but they are easy to found). Those who worked basically consisted in altering my previous posts to give an id to each of the pre that I had used before which was unacceptable for me. So here is the solution that I came up with by inspiring myself of the different workarounds out there .

Basically what my workaround does is to delay the moment where the Highlighting will be performed to after the posts content has been loaded and then iterate through all the appropriate html tags in your code and apply highlighting


1.- Add SyntaxHighlighter's CSS resources in the template's head


<head>
     
      <link href='http://alexgorbatchev.com/pub/sh/3.0.83/styles/shCore.css' rel='stylesheet' type='text/css'/> 
      <link href='http://alexgorbatchev.com/pub/sh/3.0.83/styles/shThemeMidnight.css' rel='stylesheet' type='text/css'/>

   

2.- Add Javascript resouces and snippet to delay the script's bootstrapping at the bottom of the page (before the body closing tag




     

      <script src='http://alexgorbatchev.com/pub/sh/3.0.83/scripts/shCore.js' type='text/javascript'/>
      <script src='http://alexgorbatchev.com/pub/sh/3.0.83/scripts/shBrushJava.js' type='text/javascript'/>
      <script src='http://alexgorbatchev.com/pub/sh/3.0.83/scripts/shBrushSql.js' type='text/javascript'/>
      <script src='http://alexgorbatchev.com/pub/sh/3.0.83/scripts/shBrushXml.js' type='text/javascript'/>
      <script src='http://alexgorbatchev.com/pub/sh/3.0.83/scripts/shBrushXml.js' type='text/javascript'/>
      <script src='http://alexgorbatchev.com/pub/sh/3.0.83/scripts/shBrushBash.js' type='text/javascript'/>
      <script src='http://alexgorbatchev.com/pub/sh/3.0.83/scripts/shBrushJScript.js' type='text/javascript'/>
      <script src='http://alexgorbatchev.com/pub/sh/3.0.83/scripts/shBrushPerl.js' type='text/javascript'/>
      <script src='http://alexgorbatchev.com/pub/sh/3.0.83/scripts/shBrushPlain.js' type='text/javascript'/>
      <script src='http://alexgorbatchev.com/pub/sh/3.0.83/scripts/shBrushScala.js' type='text/javascript'/>

     <script language='javascript' type='text/javascript'>
       
          // define usual options
           SyntaxHighlighter.config.bloggerMode = true;  
           SyntaxHighlighter.config.clipboardSwf = 'http://alexgorbatchev.com/pub/sh/2.1.382/scripts/clipboard.swf';
        
            function doHighlights(){
           
   
              if(jQuery("pre").length > 0){

                     if(hasConsole()){
                        console.log("About to highlight fields");           
                     }

                     jQuery("pre").each(function( index ) {  SyntaxHighlighter.highlight(undefined, jQuery( this ).get(0));   });

              }
          }

      

          function hasConsole(){

         return typeof console != "undefined";
         } 
          

         setInterval(doHighlights, 500);
  
  </script>
</body>



Please note a few things :
  • I tried using jQuery's document ready which I find more elegant than the JavaScript timeout but it didn't work probably because it was still executed too early
  • Here running the highlight function every 500 milliseconts which I know it's not great...
  • Finally please note that the above code snippet will apply to all the pre tags in your code (which is OK for me since I only use them to display code) but it might affect your blog layout if you use them for other purposes; in that case just modify the script to check for CSS classes corresponding to those used by SyntaxHighlighter

Testing email sending functionality with a free mock smtp server

Intro

Often web applications include some email sending functionality that you have to develop/and test and there are certainly a lot of way to do this, use a fake-email recipient, use a dummy email recipient, spam your colleagues, etc. and there are some advantages and drawbacks to each of these approaches.

Recently I had to do some maintenance on an application that would send a massive amount of emails (mailing list) and I needed to test if everything was still working properly after the code modifications and since I had to change the application to allow sending multi-part messages with attachments there was a possibility that something was broken in the process.

Now for obvious reasons I could not test this in the production environment as it will have an impact on the company's SMTP server and the poor souls receiving an indecent amount of emails so I needed a mock or fake SMTP server to emulate this...

A solution

I present you Fake SMTP server. This great little Java program allows you to easily test your email sending functionality without side-effects (like spamming all your colleagues) by mimicking a real SMTP server.

Once the server is started and listening it will provide you with a list of received emails as well as SMTP logs and RAW email data and it works for both "simple" and MultiPart emails with attachments

How to use it ?

Just download it, unzip it and run it:

[/home/ufasoli/tools/smtp ~] java -jar fakeSMTP.jar

this will start the GUI but not the server for that you will need to click on the "Start server" button

There are also a few command line options that you can provide when starting the server like for example to start the server automatically :

  • -o : Change the output directory
  • -p : Change the listening port
  • -s : Start the server automatically when you run the GUI

As indicated by the author on the websites there are a few alternatives :

Requirements

The only thing you need to run this server is JVM 1.6+. Please also note that if you run this on a Unix/Linux environment you will need root privileges to listen on the port 25

Keeping alive a SSH connection or in my case a multi-hop ssh tunnel to prevent timeout

A few months ago I wrote an article on how to create a multi-hop SSH tunnel between 3 machines

Since then I have been using this a lot for one of the projects I'm working on but I was annoyed that whenever the connection went idle for more than 2 minutes (like if I was reading an article or answering an email) the connection will be dropped abruptly and I will have to start it all over again...

After playing a bit with SSH options and reading ssh man I finally found my salvation, that is the -o flag with 2 options :

TCPKeepAlive
Specifies whether the system should send TCP keepalive messages to the other side. If they are sent, death of the connection or crash of one of the machines will be properly noticed. However, this means that connections will die if the route is down temporarily, and some people find it annoying. On the other hand,if TCP keepalives are not sent, sessions may hang indefinitely on he server, leaving host users and consuming server resources. The default is "yes" (to send TCP keepalive messages), and the server will notice if the network goes down or the client host crashes. This avoids infinitely hanging sessions. To disable TCP keepalive messages, the value should be set to "no".
ServerAliveInterval
Sets a timeout interval in seconds after which if no data has been received from the server, ssh will send a message through the encrypted channel to request a response from the server. The default is 0, indicating that these messages will not be sent to the server. This option applies to protocol version 2 only.

Below is the line of code that I use to create my multi-hop SSH tunnel and to prevent it from getting disconnected when idle :

ssh -o TCPKeepAlive=no -o ServerAliveInterval=15 -v -L38080:localhost:38080 ufasoli@host1 -t ssh -o TCPKeepAlive=no -o ServerAliveInterval=15 -v -L38080:localhost:38080 ufasoli@host2 -t ssh -o TCPKeepAlive=no -o ServerAliveInterval=15 -v -L38080:localhost:8080 ufasoli@host3

Here I'm disabling the TCPKeepAlive option on all the SSH chained connections and sending a message through the tunnel every 15 seconds to keep the data flowing

Please note that disabling the TCPKeepAlive option might be frowned upon by your IT Linux Guru / System administrator since as stated in the manual can keep alive dead connections (like if you forget to close your connection) so be careful when using these options and do not forget to properly close your SSH connection / tunnel. Also as I always say, I'm no Linux Guru so I'm not aware of the possible side-effects of this options so use them at your own risk !

MongoDB using MapReduce to filter fields by text content

Let's say that we want to filter a list of documents and extract only those in which the text of one of the fields matches a given constraint, for example a word that is repeated in the text

For this example I will be doing it using MongoDB's MapReduce


   {
      "_id" : "507f191e810c19729de860ea",
      "txtField" : "Lorem ipsum dolor sit amet, consectetur adipiscing elit. Phasellus mauris arcu, lacinia a pharetra id, rhoncus in lorem. Morbi tempor consequat ante, vel porta tellus lacinia id. Phasellus vel nisi vitae velit pulvinar tincidunt non id massa. "
}


Below is the Map/Reduce functions that I will be applying to filter my results the results :

1.- Map Function


   
   function Map() {
 
     // count the number of times the regexp is matched in the text for the field txtField
     var count = this.txtField.match(/lorem/gi);

    // emit the result when the pattern has been matched at least 2 times
    if( count != null && count.length > 1){ 
       emit(this._id,count);
   }    
 
}

2.- Reduce Function



   function Reduce(key, values) { 
      return values[0];
   }

3.- Full query


  db.runCommand({ 
       mapreduce: "MY_DOCS", 
       map : function Map() {
            var count = this.txtField.match(/lorem/gi);
    
           if( count != null && count.length > 1){ 
             emit(this._id,count);
           }    
    
 
       },
      reduce : function Reduce(key, values) {
         return values[0];
      },
      query : { "txtField" : { "$exists" : true } },
      out : { inline : 1 }
  });

You can find additional info on MapReduce operations this nice article

Custom number formatting in JSP with JSTL for a given locale

So this one was pretty painful to resolve and I spent a few hours struggling with it.. especially since I haven't work with JSP for A WHILE...

Usually when you need to format a given number (in my case a BigDecimal) you can use the fmt:formatNumber tag if you have setted your locale properly it should use the appropriate decimal separator according to the language.

However this time it wasn't working and I'm really not sure why, other fields in which I was using the spring tag spring:bind the output was properly formatted

I needed to output a large number using grouping separators (by groups of 3) and at least 2 decimals

What I was trying to accomplish was to have a number with Swiss grouping and decimal separators like this 2'300'120.40 but I was getting this 2 300 120,40

I tried a lot of things, like setting the locale for the page using the setLocaletag


   

Forcing the pattern when calling the formatNumber function


   

And different combinations of values for the different attributes of the formatNumber tag, such as type="currency" nothing worked!! and the spring:bind just stood there gloating !!

It would have been great if the formatNumbertag would allow you to force the grouping and decimal character that would be used, but it's just not possible.

Luckily however this can be done in Java using the java.text.DecimalFormat ; and java.text.DecimalFormatSymbols

Since I was running out of time the workaround that I found was :

  1. Create a Util class in Java with a static method that would do the formatting and conversion how I wanted it to be done
  2. Declare this static method as a custom JSTL tag
  3. Call this function with my number as argument to obtain the formatted String
  4. Go enjoy a coffee :)

Below are the code snippets I used

The Java util method :


  public static String bigDecimalToFormattedString(BigDecimal bd)
  {
    String formattedString = null;
    try
    {
      DecimalFormatSymbols symbols = new DecimalFormatSymbols();
      symbols.setDecimalSeparator('.');
      symbols.setGroupingSeparator('\'');
      
      String strange = "###,###.##";
      
      DecimalFormat chCurrencyFormat = new DecimalFormat(strange, symbols);
      chCurrencyFormat.setGroupingSize(3);
      chCurrencyFormat.setMinimumFractionDigits(2);
      
      formattedString = chCurrencyFormat.format(bd);
    }
    catch (Exception e)
    {
     logger.error(String.format("Unable to convert BigDecimal : %s to String. error : %s", new Object[] { bd, e.getMessage() }));
    }
    return formattedString;
  }

You will need then to declare your custom functions in a .tld file that needs to be placed under the WEB-INF :




    Custom Functions    
    1.0
    http://java.sun.com/xml/ns/javaee:cf

    
      Converts a given BigDecimal to a formatted String with decimal and grouping separators
        bd2s
        com.ufasoli.StringUtils
        String bigDecimalToFormattedString(java.math.BigDecimal)      
    

Once this is done you can use your custom functions by simply importing the taglib in a JSP file


<%@taglib prefix="cf" uri="http://java.sun.com/xml/ns/javaee:cf"  %>
.....
......

Now all of this can certainly be improved like by allowing the user to override the pattern, or the grouping separator, but in my case the output would be the same formatting throughout the application so I didn't need them. Regarding the hyper generic I know it's a really bad practice and should not be used but in this case we needed a quick and dirty solution that will not cause the app to fail if an exception occurred when formatting a given number

Angular6 hiding component selector

It's sometimes useful to have angular's component selector not to be rendered in the page, as sometimes this can cause problems with...