Creating Java Command Line Applications using jLine

  • Posted by Chathurika Sandarenu
  • Friday, November 18, 2011
Most common way of writing a command line application in java is to use BufferedReader to read user input. But if you want more features like tab completion, you have to write code to handle it from the scratch in BufferedReader method.

There is a nice library called jLine http://jline.sourceforge.net/ which can be used to write nice CLI apps without much effort. It has out of the box support for;

  • Command History 
  • Tab completion 
  • Line editing 
  • Custom Key Bindings 
  • Character masking
I've written simple sample application on how to use jLine. You can check that out in github https://github.com/sandarenu/sample-apps/tree/master/java-cli-app. 
 

Another Tech Genius Passed Away...

  • Posted by Chathurika Sandarenu
  • Monday, October 17, 2011












Dennis Ritche, co-author of C programming language and one of the creators of Unix operating system has passed away last week. His inventions changed the way how we do things in the computer industry.
Thank You Dennis....

It is really sad to see that two of the great minds in technology world passed away in a month...
 

Remembering Steve Jobs

  • Posted by Chathurika Sandarenu
  • Thursday, October 06, 2011
Steve Jobs, one of the greatest visionaries of our time has passed away on Wednesday(5th Oct 2011). He was 56.

At 2005 Stanford address quated on his own mortality, saying:
“Remembering that I’ll be dead soon is the most important tool I’ve ever encountered to help me make the big choices in life. Because almost everything — all external expectations, all pride, all fear of embarrassment or failure - these things just fall away in the face of death, leaving only what is truly important.”

 

How to Use Multiple GIT Accounts

  • Posted by Chathurika Sandarenu
  • Thursday, September 08, 2011
Yesterday at HMS we moved some of our projects to GIT from SVN repository. So in order to access that office GIT repository I had to create a new ssh key using my office email address. I already had a ssh key which I used to access my GitHub account. So once I created new key I was unable to access GitHub since in normal configuration ssh can only have one public key.
But I wanted to find a way which I can use both office GIT server login and my GitHub login. After doing some searching on google I found a solution to that. For that we'll have to create ssh config file. So I created following config file at my .ssh folder
vi ~/.ssh/config

# hms-git
Host hms-git
  HostName git.myoffice.com
  User git
  IdentityFile /home/sandarenu/.ssh/id_rsa

# github
Host github.com
  HostName github.com
  User git
  IdentityFile /home/sandarenu/.ssh/id_rsa_github

 Once this config file is saved I could clone office git projects using
  git clone git@hms-git:myproject

To clone GitHub project I could use
  git clone git@github.com:sandarenu/task_tracker.git
 

Using SoapUI for Web Service Testing

  • Posted by Chathurika Sandarenu
  • Friday, July 08, 2011
SoapUI is a great tool which can be used to test web services. In this post I'll show you how to set up SoapUI project for WS testing.

Create new project from File ->New SoapUI Project, and in "New Project Dialog" give name and the location of the WSDL file.


You can find the sample wsdl file I used for testing in github https://github.com/sandarenu/soapui-test.

Web Service Mocking

Service mocking is required when you are writing a web service clients and either you don't have the web service implemented or you don't have the access to the real service. Here's how to do that using SoapUI.

Create Mock of the web service by right clicking on the project and selecting 'Generate MockService'.

Once mock service is created you can mock the operations by clicking on the small icon in the service mock dialog.




Double click on the operation you just mocked and you'll get a dialog to configure mock responses.
You can configure any number of mock responses and then select how those response to be dispatched when our mock service receives WS request. There are many dispatching strategies available such as "Script", "Sequence", "Query Match", etc...

When you do some integration testing you need your mock service to respond based on different parameters of the requests you send. In such cases you can either use "Script" or "Query Match" dispatch mechanism.

Web Service Testing
We can use SoapUI to create test cases to test a Web Service we developed. To create a test suite right click on the project and select "New TestSuite" from the context menu. Then right click on the test suite we just created and select "New TestCase".



Once we have created the test case we can add test steps to it. Lets add a test step to test time for time zone 'lk'. Right click on the test steps dialog and select "Test Request" and create the request you want to test.
Once test request is created we can add assertion step to it. Click the "Assertions" button at the bottom of the test request editor.


Right click on the assertion editor and add "xPath Match"

 Put //Time as "xQuery Expression" and put value you are expecting as "Expected Result"

Now you can test this request using the Mock WS you created before. Start the mock service by clicking on the small green arrow found in the top of the "TimeServiceMock". Then open the test case you created above by double clicking it. Then run the test case again by clicking small green arrow in the to of the dialog box.


If every thing went well you'll be able get success result for your test case.

This is just the start. You can then add more test cases and assertions and improve your test suite. SoapUI site has good documentation on how to do functional testing. http://www.soapui.org/Getting-Started/functional-testing.html
You can refer that and get more information.

You can also find the SoapUI project for this example at https://github.com/sandarenu/soapui-test. Download it and open it using "File -> Import Project"

Happy Testing.....
 

Solving 'symbol lookup error' in new Eclipse 3.7 Indigo in Fedora

  • Posted by Chathurika Sandarenu
  • Sunday, July 03, 2011
When I downloaded and run the latest eclipse 3.7 Indigo release, it crashed with a strange error.

symbol lookup error: /usr/lib/libwebkit-1.0.so.2: undefined symbol: soup_content_decoder_get_type

After some searching in the web I found out that it is due that I'm having an older version of libsoup library. I had libsoup-2.28.1-1.fc12.i686 in my fedora 12.
Issue was solved by updating that library using yum.
yum update libsoup

 

Hibernate HQL Select Query Based on Item in a One-to-Many Relationship

  • Posted by Chathurika Sandarenu
  • Friday, May 06, 2011
Few days back I had a situation where I have to fetch some data based on a value of an item stored in one-to-many relationship. I my project I had two classes like below. I had to fetch all the Oders that has particular item.

class Order {
    private List<Item> items;
    //more code ...
}

class Item {
    private String itemId;
    private String name;
    //more code ...
}

With native SQL it was not that difficult, but since I've used Hibernate I wanted to find a way to do it in HQL. After some searching in Google I found out how to do it.

select o from Order o left join o.items its where its.itemId = :itemId
 

Different views for your blog

  • Posted by Chathurika Sandarenu
  • Thursday, April 21, 2011
Recently Blogger started providing different views for the blogs created in it. They are very cute way to view our blogs in different angles. Following is snapshot view of my blog.
 

After Long Time.......

  • Posted by Chathurika Sandarenu
Its being long time since my last post......
Hopping to do some posts more frequently in coming months. So keep your fingers crossed :)
 

MySql - Ms Sql Server Database Portability

  • Posted by Chathurika Sandarenu
  • Tuesday, May 04, 2010
Few weeks back I was given a task to migrate a Java application using MySQL as its database to MS SQL Server. It was actually not a full migration, rather application should be able work with both MySQL and MS SQL Server. Since we had used Hibernate in our application I thought it will be a easy thing. But when I dig deep in to the application and started migration I was proved to be wrong. I encounter lot of issues and hence thought of documenting them so any one can get some help. Major headache was the difference in some direct SQL commands used in the application. Following are the list of issues I encounter and how I solved them.


1. JDBC Driver Issue with the Microsoft JDBC Driver
    First thought of using JDBC driver provided by Microsoft for MS SQL Server 2005.  But when I ran the test cases I got few issues with it.
    1). Gave execption "org.hibernate.MappingException: No Dialect mapping for JDBC type: -9 "
        After some investigation found out that it was due to NVARCHAR datatype. There is another opensource driver called jtds. Which is more actively developed as well. With that driver I did not get that MappingException.

2. Data type differences
    For queries like "SELECT count(id) From myTable", MySql JDBC driver returns datatype java.math.BigInteger and with MsSQL jtds JDBC driver we get datatype java.lang.Integer. So I had to convert it to string first and then convert to long
    String countStr = summaryRow[1] == null? "0": String.valueOf(summaryRow[1]);
    long count = Long.parseLong(countStr);

3. Nullable Unique columns not supported in MsSql Server. In Sql Server NULL is taken as a value and hence can't have multiple rows with null, but in MySql we can have Nullable unique columns. So when table schema is generated through Hibernate we have to execute additional update query to perform a workaround for this issue. Here we add new column called 'my-table_id_add' to the table.

declare unique_key_list_my-table cursor for
    select OBJECT_NAME(OBJECT_ID)
    FROM sys.objects
    WHERE type_desc LIKE '%CONSTRAINT' and OBJECT_NAME(OBJECT_ID) LIKE 'UQ__my-table%'

OPEN unique_key_list_my-table
    FETCH NEXT FROM unique_key_list_my-table INTO @keyName
    set @RowNum = 0
    WHILE @@FETCH_STATUS = 0
    BEGIN
      set @RowNum = @RowNum + 1
      print cast(@RowNum as char(1)) + ' ' + @keyName
      if not @keyName is null
      begin
           select @sql = 'ALTER TABLE [my-table] DROP CONSTRAINT [' + @keyName + ']'
           execute sp_executesql @sql
      end
        FETCH NEXT FROM unique_key_list_my-table INTO @keyName
    END
CLOSE unique_key_list_my-table
DEALLOCATE unique_key_list_my-table

ALTER TABLE my-table ADD my-table_id_add AS (CASE WHEN my-table_id IS NULL THEN CAST(id AS VARCHAR(30)) ELSE my-table_id END);
ALTER TABLE my-table ADD CONSTRAINT UQ__my-table_my-table_id UNIQUE(my-table_id_add);


4. TIMESTAMP in MS Sql server is not functionally same as MySQL. Have to use GETDATE() function for that.
    e.g: Create table timestamp_test DATETIME default(GETDATE())

5. In Ms Sql Server we can't use 'user' as table/field name, but that is possible in MySql.

6. LIMIT is not supported in Ms Sql Server and there is no easy way if we want go select some range of data. In MySql we use "SELECT * FROM my-table LIMIT 10, 20" to select records from 10 to 20, but in Ms Sql Server we have to use something like "SELECT * FROM ( SELECT *, ROW_NUMBER() OVER (ORDER BY id) as row FROM my-table ) a WHERE row > 10 and row <= 20"
 

Integrating YUI Compressor to your Maven Web Project

  • Posted by Chathurika Sandarenu
  • Wednesday, February 17, 2010
Size of the javascript files and css files in a website has a big affect on its performance. Especially in slow connections lot of time will be spent on downloading those files. We recently came across such situation. Our website was using jQuery and some other javascipt libraries. Some of them were more than 100kb. Sometimes it took more than 10 seconds to load a page. When we view the loading statistics using developer-tools in Chrome it showed that browser had downloaded more than 500kb of scripts and css.

One way to reduce this script size is to compress them. Our script files contained lot of comments, licencing statements, nice formattings, long meaningful variable names etc... which increases the file size. YUI Compressor is a free utility by Yahoo which can be use to compress our scripts by removing above mentioned things. It is jar file and you can use that and compress file by file.

But that is not very practicle to keep those minimized scripts in develepment since after minimizing you won't be able read them and edit them when needed. Best method is to do the minization when you create the war file. Luckly there is a maven plugin for this. Following is the plugin component you can add to your maven pom.


<plugins>
....
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-war-plugin</artifactId>
<configuration>
<webResources>
<resource>
<directory>
${project.build.directory}/minimized
</directory>
<targetPath>/</targetPath>
<filtering>false</filtering>
</resource>
</webResources>
</configuration>
</plugin>
<plugin>
<groupId>net.sf.alchim</groupId>
<artifactId>yuicompressor-maven-plugin</artifactId>
<version>0.7.1</version>
<executions>
<execution>
<goals>
<goal>compress</goal>
</goals>
</execution>
</executions>
<configuration>
<webappDirectory>
${project.build.directory}/minimized
</webappDirectory>
<nosuffix>true</nosuffix>
</configuration>
</plugin>
....
</plugins>



When you run mnv clean package YUI compressor will compress the scripts and put them in target/minimized folder and those will be used to create the war file.
 

8 Stages of Programming a New Feature

  • Posted by Chathurika Sandarenu
  • Friday, January 15, 2010
This is a really nice comic I came across few days back. It is really nice and explains every thing what we generally going through as software engineers.....



This one was originally published at http://www.my25percent.com/2009/09/eight-stages-of-programming-new-feature.html 

 

Happy New Year 2010

  • Posted by Chathurika Sandarenu
  • Friday, January 01, 2010

Wish You All a Very Happy and Prosperous 
New Year!
May All Your Dreams Come True in This Wonderful Year...
 

Traditional SDP Vs mChoice Soltura

  • Posted by Chathurika Sandarenu

SDPs are commonly developed as core systems which interconnect different Telco network services and provide one unified access point for customers (application developers). This will reduce the application development cost rapidly and easy management of applications for the Telco. Even though SDP reduces the application development cost, still the most difficult part remains; which is the development of the business logic of the application. With SDP model if any content provider wants to run a mobile application, then they have to consider about two things;
  1. Developing/running and maintaining the application
  2. Managing the content provided by the application
These two are completely different things. For a genuine content provider 'Developing/running and maintaining' an application is a completely new thing and it will deviate his concentration from providing valuable content. In addition to that, content provider also has to bear the cost of infrastructure required to run the application. Initial cost of developing the application and buying infrastructure can be really high. This startup cost is one of the main reasons blocking many of the new comers entering to the market. 


This is where the mChoice Soltura TM come in to the scene. mChoice Soltura is not just a SDP, rather it provides infrastructure for content providers to create their own application with virtually zero cost. They don't have to worry about creating applications, maintaining them and infrastructure requirements to run those applications. They can put 100% of their attention to the creation of the content. mChoice Soltura will provide different types of applications, so the content provider can choose the application matching to their requirement and use it. mChoice Soltura provides a simple and powerful Web Based Interface for content provider to create/manage application and manage content. 


mChoice Soltura releases the burden of application creation, maintenance and infrastructure management and brings the freedom to the content providers.  
 

Reducing the Time Between SCTP Message Received and SCTP_SACK Sent

  • Posted by Chathurika Sandarenu
  • Saturday, November 14, 2009
Last few weeks I was involved with a development related to SCTP protocol in Java. I have also done two posts on how to get started with SCTP. During that project I came across a strange issue. That is I receive two responses for all the packets I send to the peer. After doing some investigation we found that it is due to that from my application SCTP SACK message is sent after 200ms. Because of that delay peer thinks that I have not received the message and sent it again.
That 200ms is a configuration based on the SCTP RFC. According to that an acknowledgment(SACK) should be generated for at least every second packet received, and SHOULD be generated within 200 ms of the arrival of any unacknowledged DATA chunk.So to fix this issue I had to find a way to reduce the delay between message receiving and SACK sending.
We can reduce that time delay by editing the value of /proc/sys/net/sctp/sack_timeout property file. Just use following to set timeout to 50ms. 
echo 50 > /proc/sys/net/sctp/sack_timeout
After doing that that two response issue was fixed.  Thanks Chris at sctp-dev@openjdk.java.net for helping me on fixing this issue.


, , ,
 

Catching JVM Shutdown event

  • Posted by Chathurika Sandarenu
  • Friday, October 16, 2009
Shutdown hook is a mechanism provided by java for us to handle shutdown event of our applications. We can attach any piece of code to this and execute them just before JVM exits.

public class ShutDownHookTest {
      public static void main(String [] args) throws Exception {
              System.out.println("System Started...");

                Runtime.getRuntime().addShutdownHook(new Thread( new Runnable() {
                      public void run() {
                              System.out.println("System is Shutting Down...");
                      }
              }));

              Thread.sleep(10000);
      }
}


Compile and run this sample code and press Crt+C to exit the application, you can see that "System is Shutting Down" message prints before application exiting.

But we have to be careful when using this, because if the shutdown code we attach to the shutdown hook end up in an infinite loop, our application will be stuck and only way to exit will be killing the process.
 

InfoQ allow you to download Mp3s

  • Posted by Chathurika Sandarenu
  • Friday, September 25, 2009
Finally, a feature I was waiting for long time has been included to InfoQ. Now they give the mp3 files of the presentations posted in the site. Previously we had to use some tools to capture the streaming flash video and convert them in to mp3.

 

Command Line Client for JMX

  • Posted by Chathurika Sandarenu
  • Saturday, August 08, 2009

JMX is a mechanism where we can used to monitor and control our java applications remotely. We can expose variables and methods to outside using JMX.  To access these exposed variables or methods, we have to use JMX Client. JConsole is the JMX client application shipped with Java. It is a swing based application.

There is nothing wrong with JConsole if I'm using it in from my desktop. But issue is when I want to run it on a remote machine through ssh, I can't use X because of bandwidth limitations. So ideal tool for such situation is to use CLI tool.

After searching few minutes in goolgle I found this cute little tool called "Jmxterm (JMX  Terminal)". It is again a Java application and give you all the features you need when you use JMX. It is really user friendly as well. It has auto command completion and also can remember previous command you used. It is just like bash.

[sandarenu@localhost jmx-commandline]$ java -jar jmxterm-1.0-alpha-4-uber.jar
Welcome to JMX terminal. Type "help" for available commands.
$>help
#following commands are available to use:
about    - Display about page
bean     - Display or set current selected MBean.
beans    - List available beans under a domain or all domains
bye      - Terminate console and exit
close    - Close current JMX connection
domain   - Display or set current selected domain.
domains  - List all available domain names
exit     - Terminate console and exit
get      - Get value of MBean attribute(s)
help     - Display available commands or usage of a command
info     - Display detail information about an MBean
jvms     - List all running local JVM processes
open     - Open JMX session or display current connection
option   - Set options for command session
quit     - Terminate console and exit
run      - Invoke an MBean operation
set      - Set value of an MBean attribute

$>jvms
2686     ( ) -
12216    ( ) - jmxterm-1.0-alpha-4-uber.jar
12200    ( ) - hsendidmobile.ss7.sampleapp.performance.ApplicationStarter
$>open 12200
$>bean Performance:name=smsSender,type=map
#bean is set to Performance:name=smsSender,type=map
$>info
#mbean = Performance:name=smsSender,type=map
#class name = hsendidmobile.ss7.sampleapp.performance.sms.ForwardMoSenderMBean
#there is no attribute
# operations
  %0   - int currrentTps()
  %1   - void sendMessage()
  %2   - void sendTps(int p1)
  %3   - void sendTpsParallay(int p1,int p2)
  %4   - void stopSending()
#there's no notifications
$>run sendMessage
#calling operation sendMessage of mbean Performance:name=smsSender,type=map
#operation returns:
null

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Download Presentation Videos from InfoQ

  • Posted by Chathurika Sandarenu
  • Saturday, July 11, 2009

InfoQ is a very resource full web site for anyone in the software industry. They have lot of articles, white papers, and presentations in various topics related to software engineering. Presentation videos found in InfoQ have being recorded during various conferences and are really useful. I really love watching those videos since it is great opportunity to listen to industry experts.

But the problem was that I had to sit in front of the browser and watch those videos. So I though of downloading those videos watch them when I have free time, or when I'm traveling. So I tried to download the flv using many of the free tools available in the web. But they were not successful at all. After many unsuccessful attempts, I found a way to download those presentations. It is a tool called Grub-Pro coming with Orbit-Downloader. Here is the tutorial for it. Only issue with this tool is that you have to use Internet Explorer. But no worries, as long as I can download the video, I don't mind even using IE for a while :)

grub-pro-in-IE

grub-pro-download

 

Task Focused Programing with Mylyn and TaskTop

  • Posted by Chathurika Sandarenu
  • Sunday, June 14, 2009

Few days back I came across this presentation at InfoQ site regarding "Eclipse, Mylyn and the TFI". I've seen the Mylyn view in the Eclipse and my idea about that was like some kind of a task management tool that comes with Eclipse IDE. After watching the vide my idea about Mylyn changed a lot and I was really exited about Mylyn and wanted to give it a try.  Mylyn is an open source product, there is a commercial version as well, which is called TaskTop. In task top there is a free version called "TaskTop Starter" which has some more features like Time Tracking.

Installing Mylyn and TaskTop

Mylyn comes by default with many of Eclipse editions. I was using Eclipse JEE Developer edition and it already had Mylyn. So most probably you also having it already. If you don't have Mylyn pug-in already installed in your Eclipse you can get it from Eclipse site. It has all the instruction you need to install it.

Once you install Mylyn you'll get a new view called "Task". If it is not already shown you can get it from Window -> Show View -> Other.

task-view

To install TaskTop starter edition follow the instructions given in TaskTop site. Before installing TaskTop you should do a complete update of your Eclipse. Otherwise you'll get some errors regarding incompatibilities.

Some Interesting Features of Mylyn/TaskTop

Mylyn is all about task focused programing. It allows you to do multitasking with ease. When you create a task all the editors you open are attached to that task. So when you move to another task you can see all the file which you had opened already there. You don't need to waist time on opening and closing editors when switching from one task to another.  Trust me this can improve your productivity many times. I personally experiences this during last tow days

I used mylyn.

task-list

creating-new-task 

You can also integrate bug reports from common bug tracking systems like bugzilla and Jira. Most interesting thing about this is that you can share how you fix the bug with other developers as well. Lett's say you had to open 5 files and do changes in order to fix the bug. When you mark the bug as Fixed you can also attach Mylyn context as well. So when other open it, mylyn will automatically open the files you have opened when you fixed that bug.

Another interesting thing is you can see how you have spent your time on various tasks you have performed during the day. This feature comes with the TaskTop Starter.

time-tracking

There are many more interesting things regarding Mylyn. This is only an enlightment article. If you are interested you should watch that InfoQ video.

 

 

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