Updating the hosts file in MAC

echo '172.16.144.128 hdp hdp' | sudo tee -a /private/etc/hosts

Bash script to rename or move files from a directory !

Following is the bash script that renames a sets of file form the current directoy. In the following is just updating the extension.

#/bin/bash

for file in *.JPEG; do

        name=$(basename "$file" .JPEG)

        mv "$file" "$name.jpeg"

done

Git - more on Git Tags -

The following steps outlines the Git Tag delete process both locally and remotely.

1.  Fetch all the tags from
   git fetch --tags
2. Delete the tag locally
   git tag -d yourTagToDelete  (eg: git tag -d v1.15.0)
3. Delete the tag in Remote
   git push origin :yourTagToDelete (eg git push origin :v1.15.0)
4. Create a new  tag locally
   git tag yourNewTag  (eg: git tag v1.15.0)
5. Push tag to Remote
   git push origin yourTagToDelete (eg git push origin v1.15.0)

Restarting Spring Boot Application !

Restarting Spring Boot Application  !

You have several options to restart Spring boot Application . You can restart either of the following three options. Based on your requirement you can choose one of the following.

1. Using spring-boot-devtools
           Add your Gradle dependency

    dependencies{ 
                compileOnly("org.springframework.boot:spring-boot-devtools")
  }

    After that Add, you can simply add an end poing on your controller class and have the following:
          org.springframework.boot.devtools.restart.Restarter.getInstance().restart();   

The drawback of using tools is you cannot make a good used of @Cacheable . it might cause ClassCastException while reading from the cache.


2. Using RestartEndPoint from 
   Add your Gradle dependency

  dependencies{ 
     compile "org.springframework.boot:spring-boot-starter-actuator"
  }

    After that Add, you can simply add an end on your controller class and have the following:

   @Autowired
   RestartEndpoint restartEndpoint;
   
  And call the following methond from your controller :
  restartEndpoint.restart() 
     
You might see NullPointer Exception while trying to bring the application up specially when you have UnderTow as your servlet container 

 3.   And the third one is reading the current context and restarting it. You can simply add the following method on the Main Class and invoke from your controller

       public static void restart() {
          ApplicationArguments args = appContext.getBean(ApplicationArguments.class);
          Thread thread = new Thread(() -> {
          appContext.close();
          SpringApplication springApplication = new SpringApplication(MyBootApplication.class);
          springApplication.addListeners(new ApplicationPidFileWriter());
          appContext =springApplication.run(args.getSourceArgs());
        });
       thread.setDaemon(false);
       thread.start();
      }

Thread Dumping in Unix - flyway recorder !

 jcmd 8308 JFR.start duration=100s filename=tempo.jfr

Monogo Pipeline scripts !

1. Filter by an assistance of an array element in a document:

  $and:[{assessmentPeriods:{$ne:null, $exists:true, $ne: []}}  ]

2. 

Java 11 and Groovy Compatibility and JAXBContext !

If you see the following error during compile : 

FAILURE: Build failed with an exception.

* What went wrong:
Execution failed for task ':compileTestGroovy'.
> org/codehaus/groovy/ast/MethodCallTransformation


Add the folling line to your gradle file :

ext['groovy.version'] = '2.5.6'  //i.e your grovy version.


Another issues with java 11

 Unable to load class groovy.xml.jaxb.Jaxb GroovyMethods due to missing dependency javax/xml/bind/JAXBContext 

You can fix this by adding the following dependency on the latest groovy version

Useful Unix Commands

1. Count number of lines on all the files in the current folder

wc -l *

2. Count the number of files on the current directory :

ls | wc -l

3. Print all the line containing word/s in a file
grep -iw "search words" arc.log

4. Thread dumping for a process
 jcmd 8308 JFR.start duration=100s filename=tempo.jfr

Simple hack to Update System Properties and Environment variables on Window !

If you don't have a permission to edit the System variable on your local window machine, the following hack might work

Click Window and  type "SystemPropertiesAdvanced"  on Search programs and file search text option. Then, once you see the SystemPropertiesAdvanced shortcut, right click it and open it as an administrator.  You might be able to edit it now.

MySql Query to turn ON Query statistics I/O

SET STATISTICS IO ON
SET STATISTICS TIME ON
SELECT er.ReportID, er.ReportName, er.ReportNumber
FROM dbo.EmployeeReports er
WHERE er.ReportNumber LIKE '%33%'
SET STATISTICS IO OFF
SET STATISTICS TIME OFF

MySQL Nested Case SQL statements (CASE WHEN OR THEN ELSE END )

Following is an example of nested MySQL Case When or then else End statement.

select
  CASE
  When (table.field1 = '01')
    THEN
      CASE
      When (SUBSTRING_INDEX(table.field1, ' ', 1) = 'abc')
         THEN '01abc'
         ELSE 'abc'
      END
  WHEN (table.field1 = '02')
    THEN
      CASE
      When ((SUBSTRING_INDEX(table.field1, ' ', 1)) = 'def')
        THEN '02def'
        ELSE 'def'
      END
  When (table.field1 = '03')
    THEN
      CASE
      When ((SUBSTRING_INDEX(table.field1, ' ', 1)) = 'efg')
        THEN '03efg'
      ELSE 'efg'
      END
  WHEN (table.field1 = '04')
    THEN
      CASE
      When ((SUBSTRING_INDEX(table.field1, ' ', 1)) = 'pqr')
        THEN '04pqr'
      ELSE 'pqr'
      END
  END
from table ;

Is this the beginning of the end of BitCoin, Etherum and LiteCoin ? Did it really crashed today evening ??

The BitCoin was traded at $14,212 at 6:40 PM CST, December 19 2017. The price is almost 27% less than its highest value. At the time of the post of this blog, the BitCoin is now backed up to $17,149 

The Etherum was traded at $705 at 6:40 PM CST, December 19 2017. The price is almost 17% less than its highest value. At the time of the post of this blog, the Etherum is now backed up to $772 The

LiteCoin was traded at $277 at 6:40 PM CST, December 19 2017. The price is almost 37% less than its highest value of $371. At the time of the post of this blog, the LiteCoin is now backed up to $320 

Where as the Bitcoin Cash is enjoying a ride of $3100 per bitcoin cash which is almost 41% higher than its yesterday's price.

Fix for xcrun: error: invalid active developer path after updating your mac OS to Sierra

If you are geting the following error with Git or any other tools while running it on from your terminal
 xcrun: error: invalid active developer path (/Library/Developer/CommandLineTools), missing xcrun at: /Library/Developer/CommandLineTools/usr/bin/xcrun. 

 using the following command to fix it
xcode-select --install

Git Cheat Sheet

A. To List your local branchs :

•   git branch

B. How to get or fetch a remote  Branch 
   You first need to fetch and check out the remote branc

•    git fetch remote remote_branch_name (eg :  git fetch origin story2525/mytest_remote_branch)
• git checkout remote_branch_name

C. How to delete a  Branch both locally and remotely:  

1. Delete the  remote branch   

•   git push origin :branch_name or
•   git push origin --delete branch_name

2. Delete a local branch

•   git branch -d branch_name   (use -D if your branch hasn't been fully merge yet)         

D. How to rename your remote Branch : 

1. Rename branch locally

• git branch -m old_branch new_branch

2. Delete the old remote branch   

•   git push origin :old_branch            

3.  Push the new Branch  and update the upstream to point it to the new remote branch.

•  git push --set-upstream origin new_branch

E. Git Logs :

git log --oneline | grep searchString

git log --pretty=format:"%cn committed %h on %cd"| grep searchString

F. Force Push :

 git push origin refactor/mybranch —force

G: Change the remote

git remote set-url origin <>


H. Ammend message for a committed and pushed changes

 git commit --amend 
To push the changes to the branch (myBranch) on the remote repository (origin) use: 
git push --force-with-lease origin myBranch

H. Reset your branch to origin version, revert all your local commit and changes.
Plese stash your changes before you do it. git stash

git reset --hard origin/yourbranch

 I. undo the last commit and unstage all the files:

git reset HEAD~;

j. Undo the commit and completely remove all changes(Becareful !)


git reset --hard HEAD~;

K. Undo previous merge:
check the previous log :
git log
Then revert back the merge  corresponding to the commit hash
 git revert -m 1
And finally push your changes:
git push

L. Roll Back your git push

git push -f origin last_good_commit_hash:yourbranch

 example : git push -f origin 4d875f7e3e8:develop

How to check if the given string is palindrome (Recursive vs Non-recursive )

A palindrome is a word, phrase, number, or other sequence of characters which reads the same backward or forward, such as "level" or "kayak" or  "amanaplanacanalpanama" 

Following is the program to check if the given string is a palindrome.  

package com.mytech.today;


public class PalindromeClient {


    public static boolean isPalendrome (String s) {

        if(s== null) {
            throw new RuntimeException("null value passed");
        }

        int n = s.length();
        if(n==1) return true;
        else {

            for (int i=0; i < n/2 ; i++) {
                if(s.charAt(i)!=s.charAt(n-i-1)) {
                    return false;
                }
            }
        }
        return true;
    }

    public static boolean isPalendromeRecurrsive (String s) {

        if (s.length()<2) { return true;}
        else if (s.charAt(0)==s.charAt(s.length()-1)) {
            return isPalendrome(s.substring(1, s.length()-1));
        }
        else return false;

    }

    public static void main(String[] args) {
        System.out.println(isPalendrome("levvel"));
        System.out.println(isPalendrome("manaplanacanalpanama"));

        System.out.println(isPalendrome("a"));
        System.out.println(isPalendrome("jptt aefa afdaf"));

        System.out.println(isPalendromeRecurrsive("levvel"));
        System.out.println(isPalendromeRecurrsive("manaplanacanalpanama"));

        System.out.println(isPalendromeRecurrsive("a"));
        System.out.println(isPalendromeRecurrsive("jptt aefa afdaf"));
    }
}