We can now do Spring certification without going for Pivotal training. It was long due and here it is finally!
Can you take Spring certification without Pivotal Training Course?
5 Spring Framework Books for Java developers (Includes Spring Security and Spring Boot) – Best of lot
Read more: http://www.java67.com/2016/12/5-spring-framework-books-for-java-programmers.html#ixzz4hVU7visy
A simple technique on MacOS which I use every now and then when my SSH connections hang due to network disconnect. You can immediately terminate the hung SSH session by pressing ~. (tilde and dot) keys together.
http://apple.stackexchange.com/questions/35524/what-can-i-do-when-my-ssh-session-is-stuck
I use CURL for debugging my REST endpoints every now and then if I don’t want to use Postman or DHC clients. I usually like to copy paste results / statistics from command line into emails to my colleagues. This gives them a plain jane command which they can use to test themselves as well as compare their results with mine. The following article has some good pointers on how to use CURL and some very practical examples have been provided.
15 Practical Linux cURL Command Examples (cURL Download Examples)
I recently got into a situation where I had to debug around 10 servers all of which were suffering from memory issues. My java applications were slowing down after a day or so. Although its is difficult to diagnose this kind of issues which span across multiple VMs (welcome to Micro Services!) but with some little bit of scripting it is possible to see in real time the actual numbers if you manage to use tmux to multiplex multiple shell sessions stacked together. I hacked up the following command to display hostname, running war files as well as the memory statistics refreshed every 1 second on screen.
watch -d -n 1 "hostname | tr '\r\n' ' ' && printf \" \" && jps -l | grep .war | tr '\r\n' ' ' && echo "" && free -h"
I found a good link which lists good usages of the Linux command “du”.
This command allows me to see the usage in a ascending sort which is really helpful.
Tested on Linux.
du -h / | sort -h
Tested on Mac OS.
du -hs * | gsort -h
In case you don’t have gsort install coreutils.
brew install coreutils
This variation allows me to see any line which has the text “G” in it which basically allows me to see folders using space in GBs. Agreed it might give some folder names as well with “G” in it but I can bear with it.
Tested on Linux.
du -h /the/path | sort -h | grep "G"
Tested on Mac OS.
du -h /the/path | gsort -h | grep "G"
In order to setup a fully functional Sonarqube server via docker I use the following consolidated command:
docker run \
--detach \
--name=sonarqube \
--publish 9000:9000 \
--publish 9092:9092 \
--env="SONARQUBE_JDBC_USERNAME=sonar" \
--env="SONARQUBE_JDBC_PASSWORD=sonar" \
--env="SONARQUBE_JDBC_URL=jdbc:mysql://mysql:3306/sonar?useUnicode=true&characterEncoding=utf8&rewriteBatchedStatements=true" \
--link mysql:mysql \
sonarqube:5.1
This connects my dockerized mysql instance with sonar and it is able to create tables and start using MySQL properly for storing all it’s data.
In order to setup a fully functional MySQL server via docker I use the following consolidated command:
docker run \
--detach \
--name=mysql \
--env="MYSQL_ROOT_PASSWORD=abcd1234" \
--publish 6603:3306 \
--volume=~/Docker/mysql/conf.d:/etc/mysql/conf.d \
--volume=~/Docker/mysql/mysql-datadir:/var/lib/mysql \
mysql
The advantage of the above approach is that the configuration files can be defined under ~/Docker/mysql/conf.d folder on my system and it will be picked up whenever I bootup this instance. The second thing is that all information written by this instance will be stored outside of VM in the path ~/Docker/mysql/mysql-datadir on my system. So In case this VM goes away due to some unexplained reasons I can still bootup another docker instance of MySQL and point it to this data directory.
In order to install sonar I used the following approach to create database and user.
create database sonar;
grant all privileges on sonar.* to 'sonar'@'%' identified by "sonar";
flush privileges;
I needed to install a local jar file into my laptop’s local maven repository and found this article. I used this approach to install this jar file in my repo:
mvn install:install-file -Dfile=my-model-1.2.1.jar -DgroupId=com.cyberaka.my.package -DartifactId=my-model -Dversion=1.2.1 -Dpackaging=jar -DgeneratePom=true
This duly added the local jar file under appropriate group id and artifact id inside my maven repository and I was able to refer to this dependency through my project’s pom.
I needed to make SSH connection into a VM box setup inside VirtualBox which by default uses NAT. To enable this I had to setup port forwarding. This article proved useful.