Talk by Tomas Lin on Building Killer RIAs with Flex and Grails at the Groovy & Grails eXchange 2009

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Talk by Tomas Lin on Building Killer RIAs with Flex and Grails at the Groovy & Grails eXchange 2009

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Great Blogs for GORM

Hi,
  Just hit across two part Blog for GORM by Peter Ledbrook. Its kind of Must read for
every Grails dev. no matter how expert he/she is.

http://blog.springsource.com/2010/06/23/gorm-gotchas-part-1/
http://blog.springsource.com/2010/07/02/gorm-gotchas-part-2/
http://blog.springsource.com/2010/07/28/gorm-gotchas-part-3/

 

Reading i18n messages from the database with Grails

   Many Grails based applications wants to read i18n messages from some other resource instead of from static properties files. Below link gives a great explaination how you can do it if you want to read messages from DB.
http://graemerocher.blogspot.com/2010/04/reading-i18n-messages-from-database.html

Comparing Grails and Tapestry

Hi,
   Was going through some details of Tapestry to findout whats good/bad in it. Currently I am working with Grails based application for almost 1.5 Yrs. But believe me I would try to be very unbiased during this comparision.

Note: All the comments are my based on my personal likes and dislikes, so please excuse if you think otherway round ;). Your comments are welcome if you want to correct me or share your own experiences.

  Basically Tapestry and Grails both are  frameworks which gives you Convention Over Configuration platform where you can focus on your problem domain rather then settingup the environements for developement like Spring & Spring MVC configuration, Hibernate configuation etc.
  But  following are reasons why I still prefer Grails over Tapestry:

1. Tapestry is focused on UI development with Model based architecture in mind. Even though it says minimum configuration and more over convention, but didn't like the way we hare binding UI with backend as shown at http://joshuajava.wordpress.com/2008/09/11/a-glimpse-of-wicket-14-and-tapestry-5/ when we compare it with GRAILS. I feel GRAILS is much more mature in many ways.
   a.  We will still have to manage all the Hibernate Mappings (annotations) by hand. Though we do it in GRAILS in GORM way, but somehow GORM ways makes it look much readable and maintainable.

2. Like Grails there is TRAILS as well. But dont see TRAILS group really active as there is hardly in Traction there. ex. look at the JIRA summary page: http://jira.codehaus.org/browse/TRAILS#selectedTab=com.atlassian.jira.plugin.system.project%3Asummary-panel

    Trails: http://today.java.net/pub/a/today/2005/06/23/trails.html

3. Code in Tapestry still looks much more Verbose than in Grails. I mean we have to write relatively bigger code than in Grails.

4. I feels there are just ample of Grails plugin there are reusable components compared to whats are available for Tapestry based apps.

5. Environment based application behavior support in Grails is just too good to have it. Grails support to create custom environment as well that too without doing complex coding.

6. Its just too easy to write JSP taglib and template based apps which also changes relatively frequently in Grails and it can be use very extensively when you are developing a site which needs pages which gets data from multiple places and you dont want to hardwire your controller with all data.

     So basically I am not saying Tapestry is Bad. Its is good when someone is working on old frameworks like Struts/Spring only. But as a developer I would say, one someone starts working on Grails, would not prefer writing code in Tapestry atleast. Grails just so addictive ;) by its design and flexiblility :p

Some links for Tapestry:
http://tapestryjava.blogspot.com/
http://skillsmatter.com/podcast/java-jee/tapestry-5-java-power-scripting-ease
http://howardlewisship.com/screencasts/tap5-classreload-oct2006/tap5-classreload-oct2006.html
http://howardlewisship.com/screencasts/actionlink-oct2006/actionlink-oct2006.html
http://blog.taragana.com/index.php/archive/move-over-rails-we-have-grails-trails-and-now-sails/
http://moatazanany.wordpress.com/2008/09/13/boost-your-productivity-using-apache-tapestry/

Grails:
http://stateyourbizness.blogspot.com/2008/09/pessimistic-locking-with-grails.html

Grails Intro by Scott Davis:
http://www.youtube.com/watch?v=RqHwwAWXcbE
http://www.youtube.com/watch?v=gkaaOXGomzg

http://www.viddler.com/explore/oredev/videos/29/
http://naleid.com/blog/2009/10/01/batch-import-performance-with-grails-and-mysql/
http://sacharya.com/transactions-in-grails/

Grails DB Sharding Plugin

Here is the link for Grails DB sharding plugin.

Lucene Search Index

Hi,
  Sorry for not updating blog such a long time. May be I was just too lazy to do it. But I will try to not to be so lazy from nowon ;)
      Lucene is a framework which allows you to store some data that cab be indexed so that fast search operations can be performed on it. This data can actually from from any source like file system, Database, http etc.
     Data is stored in a "Document" form within by Lucene. Its is programmer's responsibility to get the data and create documents. Lucene takes responsibility to index it and make them searchable.
    Was reading on some articles to confirm the Lucene implementation in my Grails app is proper or not. Came across following few very good links for starters.


http://www.ibm.com/developerworks/web/library/wa-lucene2/?S_TACT=105AGX52&S_CMP=cn-a-web
http://www.darksleep.com/lucene/
http://www.javaranch.com/journal/2004/04/Lucene.html

MySQL Server Replication (5.0.84)

Hi all,

    Today I tried setting-up MySQL server replication for 5.0.84. Must say its kind of really easy to setup a simple replication between 2 MySQL server instances. Putting down some key points to be followed.

  Note:  Make sure that no processes are updating master server while we perform underlying operations.

   
Steps provided in this blog are applicable to both 32 bit and 64 bit version of MySQL.

Goal:
  Setup a replication of a Database "nba_hiber_test" on Master server on other Slave Server with same DB name over there.

Pre-Requisties:

If you are making Master slave for a fresh DB, where there is nothing on the Master, just create DBs on both Master and Slave DB and directly go to Step 3.

#1. Take Backup Dump of Master DB :
   If Source (Master) database is already there on some DB which is still going to act as Master server in replication environment, please export Master database using command at shell prompt as below:
   
    mysqldump --add-drop-table  -h 192.168.100.124  -u zuber -p nba_hiber_test | bzip2 -c > nba_hiber_test12Nov09_with_data.sql.bz2


      Here 192.168.100.124 was the machine on which my existing Master database is located, and that DB's name is "nba_hiber_test". This will create a compressed bzip2 file of SQL file and store it at the present working directory.


 #2. Import DB on the slave DB:
     Transfer "nba_hiber_test12Nov09_with_data.sql.bz2" to the slave machine.
     We need to put the exact copy of the Master database on the slave server before we can enable replication. To do that, import the database on the slave machine from "nba_hiber_test12Nov09_with_data.sql.bz2"

        a. Decompress "nba_hiber_test12Nov09_with_data.sql.bz2" :
       
                bzip2 -d nba_hiber_test12Nov09_with_data.sql.bz2

        b. Login to the MySQL on slave box and Create DB with same name as on the Master server (here "nba_hiber_test"):

                create database nba_hiber_test;

         c. Assuming you started MySQL client from at the same location where u ran command 2.a, run that SQL fil against "nba_hiber_test" on slave box:
       
               # start using target slave DB
                    use nba_hiber_test;
       
              # Run SQLs in "nba_hiber_test12Nov09_with_data.sql"
                    source nba_hiber_test12Nov09_with_data.sql;

        This import may take time depending upon the size of  the database and the hardware on which you are running MySQL. Use that time to go thru this whole document rather than waiting and looking curiously on the black screen ;)


  #3. What we did? :
         At this point, we have identical copy of Master and Slave dbs on bothe machines.

  #4. Configure Master server to generate bin logs that can be used pass replication info:
   This will be needed only if you are starting using this server as Master in a replication environment fpr the first time
   To confirm if server is acting as Master or not fir "SHOW MASTER STATUS;" command on mysql prompt. If no records returns, means you have to configure it for master.
  
     Add following lines inside [mysqld] of "my.cnf" file.
    
    # folder path whre mysql will store its log-bin files
    log-bin=/var/lib/mysqllogs/bin-log

    # databases for which the replication info (log-bins) to be generated
    replicate-do-db=nba_dev

    #Change server id to some unique number in the range of 0 to 2^32 - 1
    server-id       = 1 
    
     Most of the time "my.cnf" is located in "/etc" folder. You will need root access to change the file and restart the server.

  #5. Restart Master DB:
     
        /etc/init.d/mysqld restart

  #6. Confirm that bin logs are getting created:
        Login to Master DB and fire:
     
      SHOW MASTER STATUS;

    Assume its running fine if you see something like:

    mysql> show master status;
        +---------------------+----------+--------------+------------------+
        | File                | Position | Binlog_Do_DB | Binlog_Ignore_DB |
        +---------------------+----------+--------------+------------------+
        | bin-log.000001      |       98 |              |                  |
        +---------------------+----------+--------------+------------------+
        1 row in set (0.00 sec)
   
  #7. Find out the log position on which Master server points to right now :
    KEEP A NOTE OF THIS HADY to provide it to slave later:

    SHOW MASTER STATUS

  #8. Create replication user on the Master server to be used by slves to connect to do replication:

    CREATE USER 'repl'@'%' IDENTIFIED BY 'passwd';
    GRANT REPLICATION SLAVE ON *.* TO 'repl'@'%';

  #9. Configure Slave server to give details of what all databases on this server are to be popullated with replication.
        Add following lines inside [mysqld] of "my.cnf" file.
   
           skip-slave

          #Change server id to some unique number in the range of 0 to 2^32 - 1
          server-id       = 2 
 
  #10. Restart Slave DB:
     
        /etc/init.d/mysqld restart

  #11. Stop any existing Slave threads on Slave Server:

        STOP SLAVE

  #12. Setup the Master info on Slave DB:
         Note that we pass same values of "file" and "Position" in this command as found on step 7.
   
    CHANGE MASTER TO
    MASTER_HOST = '192.168.100.124',
    MASTER_USER = 'repl',
    MASTER_PASSWORD = 'passwd',
    MASTER_LOG_FILE = 'bin-log.000001',
    MASTER_LOG_POS = 98;

  #13. Chkeck the Slave thread status to see if is able to connect to the Master DB or not:

    SHOW SLAVE STATUS \G

    This commend should give you something like this as result:

        *************************** 1. row ***************************
             Slave_IO_State: Waiting for master to send event
            Master_Host: 192.168.100.124
            Master_User: repl
            Master_Port: 3306
              Connect_Retry: 10
            Master_Log_File: bin-log.000003
        Read_Master_Log_Pos: 41435
             Relay_Log_File: mysqld-relay-bin.000006
              Relay_Log_Pos: 41570
          Relay_Master_Log_File: bin-log.000003
           Slave_IO_Running: Yes
          Slave_SQL_Running: Yes
            Replicate_Do_DB: nba_hiber_test
        Replicate_Ignore_DB:
         Replicate_Do_Table:
         Replicate_Ignore_Table:
        Replicate_Wild_Do_Table:
    Replicate_Wild_Ignore_Table:
             Last_Errno: 0
             Last_Error:
               Skip_Counter: 0
        Exec_Master_Log_Pos: 41435
            Relay_Log_Space: 41570
            Until_Condition: None
             Until_Log_File:
              Until_Log_Pos: 0
         Master_SSL_Allowed: No
         Master_SSL_CA_File:
         Master_SSL_CA_Path:
            Master_SSL_Cert:
          Master_SSL_Cipher:
             Master_SSL_Key:
          Seconds_Behind_Master: 0
    1 row in set (0.00 sec)

  #14. Test:
        Now try creating some records in the Master table, and check its getting reflected in the Slave server in some interval.

  Wish you Happy Replication