CONTINUAL INTEGRATION – Page 220 – A Technical I.T./DevOps Blog

How Do You Troubleshoot the Java Error “class … is public, should be declared in a file named foobar.java”?

Problem scenario
You copied a Java program from the Internet. You named the file foobar.java. You try to compile it (e.g., with "javac foobar.java"), but you get this error:

foobar.java:6: error: class ContInt is public, should be declared in a file named ContInt.java
public class ContInt
^
1 error

What do you do?

Solution
Rename foobar.java to be ContInt.java.

A List of RESTful API Books

API Management: An Architect's Guide to Developing and Managing APIs for Your Organization by Brajesh De
APIs: A Strategy Guide: Creating Channels with Application Programming Interfaces by Daniel Jacobson, Greg Brail and Dan Woods
ASP.NET Web API: Build RESTful web applications and services on the .NET framework by Joydip Kanjilal
Build APIs You Won't Hate: Everyone and their dog wants an API, so you should probably learn how to build them by Phil Sturgeon
Building a RESTful Web Service with Spring by Ludovic Dewailly
Building RESTful Python Web Services by Gaston C. Hillar
Client-Server Web Apps with JavaScript and Java: Rich, Scalable, and RESTful by Casimir Saternos
Developing Web Apps with Haskell and Yesod: Safety-Driven Web Development by Michael Snoyman
Diving into ASP.NET WebAPI: Learn REST services in .Net : A Practical Approach by Akhil Mittal
Go Programming Blueprints - Solving Development Challenges with Golang by Mat Ryer
Grails in Action by Peter Ledbrook and Glen Smith
Introduction to JavaScript Object Notation: A To-the-Point Guide to JSON by Lindsay Bassett
Professional Java for Web Applications by Nicholas S. Williams
Pro RESTful APIs: Design, Build and Integrate with REST, JSON, XML and JAX-RS by Sanjay Patni
Rails 4 in Action: Revised Edition of Rails 3 in Action by Ryan Bigg, Yehuda Katz, Steve Klabnik and Rebecca Skinner
REST: Advanced Research Topics and Practical Applications by Cesare Pautasso, Erik Wilde and Rosa Alarcon
The REST API Design Handbook by George Reese
REST API Design Control & Management: DevOp Series by Alasdair Gilchrist
REST API Design Rulebook: Designing Consistent RESTful Web Service Interfaces by Mark Masse
RESTful API Design (API-University Series) (Volume 3) by Matthias Biehl
RESTful Java Patterns and Best Practices by Bhakti Mehta
RESTful Java Web Services - Second Edition by Purushothaman Jobinesh
RESTful Java Web Services Security by Rene Enriquez and Andres Salazar C.
RESTful Java with JAX-RS 2.0: Designing and Developing Distributed Web Services by Bill Burke
RESTful Rails Development: Building Open Applications and Services by Silvia Puglisi
RESTful Web API Design with Node.JS - Second Edition by Valentin Bojinov
RESTful Web API Handbook by Michael Bohner
RESTful Web Clients: Enabling Reuse Through Hypermedia by Mike Amundsen
RESTful Web Services Cookbook: Solutions for Improving Scalability and Simplicity by Subbu Allamaraju
RESTFul Web Service Development with Jersey 2.x by Han Sun
RESTful Web Services with Dropwizard by Alexandros Dallas
RESTful Web Services with Scala by Jos Dirksen
RESTful Web APIs: Services for a Changing World by Leonard Richardson, Mike Amundsen and Sam Ruby
REST in Practice: Hypermedia and Systems Architecture by Jim Webber, Savas Parastatidis and Ian Robinson
Restlet in Action: Developing RESTful web APIs in Java by Jerome Louvel , Thierry Templier and Thierry Boileau
Scalatra in Action by Dave Hrycyszyn, Stefan Ollinger and Ross A. Baker
Understanding RESTful Web Services by Van Nguyen

What Do You Do If You Run an Ansible Command and You Receive an Error “Failed to connect to the host via ssh: OpenSSH_6.6.1, OpenSSL 1.0.1e”?

Problem scenario
You run an Ansible command. But you get an error like this:

" UNREACHABLE! => { "changed": false, "msg": "Failed to connect to the host via ssh: OpenSSH_6.6.1, OpenSSL 1.0.1e
-fips 11 Feb 2013\r\ndebug1: Reading configuration data /etc/ssh/ssh_config\r\ndebug1: /etc/ssh/ssh_config line 56:"

What should you do?

Solution
On the Ansible control server find the ansible.cfg file (find / -name ansible.cfg). If you not using Mac OS, this stanza should not be in your ansible.cfg file:

control_path = ~/.ssh/ansible-ssh-%%C

Comment out the above stanza if you are using Ansible on Linux (e.g., Linux SUSE or a RedHat or Debian derivative). Then run your ansible command. The problem should be fixed.

The root cause is that "~/.ssh/ansible-ssh-%%C" is appropriate for MacOS deployments of Ansible and not regular Linux.

How Do You Create a New User on a Windows 2016 Server with PowerShell?

Problem scenario
You want to use PowerShell to create a local user on the server. What command do you run to do this?

Solution
1. Open PowerShell as Administrator.
2. Run this (but replace "jane" with the username you want): New-localuser -Name jane
# respond to the pop-up GUI with a password that is reasonably strong.

How Does the Dictionary Definition of Automation Relate to Software GUI Automation?

Question
How does the dictionary definition of automation relate to software GUI automation?

Answer
The most common definition (and first-listed) of the word automation on Dictionary.com's website is "the technique, method, or system of operating or controlling a process by highly automatic means, as by electronic devices, reducing human intervention to a minimum." Attended and unattended robotic process automation solutions can greatly enhance productivity and reduce the likelihood of errors. To learn more about RPA see this posting that defines it or this posting that gives insight into when it should be used.

How Do You Select More RAM to Purchase for Your Desktop and Know the Difference between DDR3 and DDR4 RAM?

Problem scenario
You want to buy more RAM for your desktop computer. You find it is frequently memory constrained (e.g., when you look at the Task Manager if it is running Windows or use the top utility from a Linux command prompt. What should you do?

Solution
Know the difference between DDR3 and DDR4 RAM. If you want to read an article about the difference between DDR3 and DDR4 RAM, see this link.

DDR4 RAM costs more. Here is a link to DDR4 RAM if you want to buy some. For buying more affordable DDR3 RAM, see this link.

Beware, many motherboards support either DDR3 or DDR4. Only a few can support either. Even then the slots themselves are dedicated to either DDR3 or DDR4; one slot can support only one type (DDR3 or DDR4) however.

Aside from the type DDR3 and DDR4, attributes of RAM that should affect the purchasing consideration include the bus speed (measured in Mhz) and the size of the RAM (measured in GB). You want your memory to perform well for the price that you pay.

A List of VMware vSphere Books

How Can Variables Be Carried across Multiple PHP Pages (Not Just Immediate Subsequent Pages)?

Problem scenario
You want to pass variables from user input and have them carry across multiple pages. You may or may not want the immediate subsequent page to use the variables. You want pages (.php files) after several clicks of navigation (two pages or more) to employ the variables that were read in or calculated via PHP pages.

You are using session_set() and/or session_start() but they are not working. Your $_SESSION['variablename'] usage is not working as you expect. What do you do to have global variables so you can take in user input from one page and have pages two pages away use those variables?

Solution
Use session_start() above any HTML code on the page after the "Submit" button was clicked. That is, on a page that has the $_POST['varname'] available, use the session_start() PHP function before any HTML code. Do not use session_set() for a modern version of PHP. Here are three pages below that can work as an illustration. To use them, you'll put them all in the same directory. The first one will read in user input. The second page acts as an intermediate page. The third page (arrived to by clicking a button on the second page), has access to the global variables which are the user input.

1. one.php should have the following content:

<html>
<body>
<h2> Welcome to page 1. Enter your credentials here.</h2>
<form action="two.php" method="post">
UserName: <input type="text" name="username"><br>
Password: <input type="password" name="password"><br>
<input type="submit">
</form>

</body>
</html>

2. two.php should have the following content:

<?php
session_start();
$_SESSION['username'] = $_POST['username'];
$_SESSION['password'] = $_POST['password'];
?>
<html>
<body>
<h2> Welcome to page 2. Click submit to proceed to the third page. </h2>
<form action="three.php" method="post">
<input type="submit">
</form>

</body>
</html>

3. three.php should have the following content:

<?php
session_start();
echo "The username you entered on the first page was ";
echo $_SESSION['username'];
echo ".";
echo "\n";
echo "This proves the variable is global.";
$var1 = $_SESSION['username']; //This is a suggestion for PHP coding.
?>

4. Go to http://x.x.x.x/one.php and enter any username and password you like. Make sure the username is not blank. Click "Submit query." Click "Submit query" again.

How Do You Quickly Install Several Python Packages Such as Pycrypto and Paramiko on RedHat Linux?

Problem scenario
How do you install pycrypto, paramiko and the several related packages without copying several individual packages on a RedHat Linux server?

Background
It can be tedious getting the different dependencies of python packages installed. By downloading various .tar.gz files, you have to unpack them, then run a series of "python setup.py ..." commands. While it is not advisable to install more packages than are strictly necessary, there are some benefits to doing it (e.g., having these features available to you).

Solution
Install pip, Ansible and other packages. Run these commands as root:

yum -y update
yum -y install java gcc python-openssl openssl-devel openssl
curl "https://bootstrap.pypa.io/get-pip.py" -o "get-pip.py"
python get-pip.py
pip install ansible

How Do You Install Java on an AWS Instance of RHEL?

Problem scenario
You are using RedHat Enterprise Linux 7.x in AWS. How do you install Java?

Possible Solution #1
Use this posting as it is preferred. Below is an alternative.

Possible Solution #2
This will install Java 1.8.x.

1. Create a file named java.sh with this as the content:

yum -y install java-1.8.0-openjdk*
JAVA_HOME=/usr/lib/jvm/jre-1.8.0-openjdk
echo 'export JAVA_HOME=/usr/lib/jvm/jre-1.8.0-openjdk' >> ~/.bashrc
source ~/.bashrc
sudo -s
sudo -s source /etc/environment

2. Run this command: sudo -s source java.sh

3. You are done. To test, you can run java -version and echo $JAVA_HOME. If you are having network issues, you may want to view this posting.