Login form using Spring MVC part 2


LoginServiceImpl class:

In the LoginController we have to modify the validation logic to use the service class for validating the user. LoginController class:

For creating full login site we should add Hibernate and MySql driver dependencies in pom.xml file. Another thing is to add applicationContext.xml file for initializing Spring and Hibernate related components. For example bean definition for MySQL dataStructure and sessionFactor which will be used in DAO classes.

Thera are also a few changes in: web.xml:

Login form using Spring MVC part 1

For Energy Billing System I want to add login screen for the user that will be displayed before access to user panel. The user can enter username and password, click submit button to proceed the login. For this purpose, I create a simple database in mysql.

Create a table called: users, by using fallowing sql:

Checking information about table that we created:

Added two records into users table:

Now in a database, we should have two records. Next step is to create a model class. This Entity is mapped to the “users” table.

Created DAO class interface:

For now is a small part of login implementation. In the next post, I will present complete implementation.


Initial controller, view and dispatcher servlet configuration

For the last few days, I have not had time to work on the project. Now there is simple page displayed as an initial project page.

Added spring framework dependencies in pom.xml file:

Simple view:


Created dispatcher servlet configuration:

The picture above presents the basic appearance of the page that will appear after run changes. For now, there are not many changes, but it is a necessary attitude to make new changes and work on the application.


Selenium Grid

Selenium Grid is a tool, that allows to runs multiple tests across different operating systems, browsers in parallel at the same time. Grid architecture contains Hub that only runs tests on a single machine, execution, however, these tests are performed on different machines called nodes.
This approach obviously has its advantages. Speeds execution of a test, otherwise the application under tests is tested simultaneously on several environments, giving additional feedback.

Selenium Grid Architecture

An architecture of grid is very simple. First, we should have a hub, only one hub in a grid. This will be our starting point and to a hub, we will load tests into. From there, tests are loaded into nodes.

Nodes are instances that will execute tests that were loaded from a hub. There can be one or more nodes, this depending on our configuration and of course needs.

To install Selenium Grid on a local machine we should make two things: first, install java JDK, and second download Selenium Server JAR file from SeleniumHq webpage.

After download, all needed files lets start with hub configuration. To start selenium grid hub on a local machine, open console and go to the directory where is located selenium server JAR file.

After that, we can open a browser and go to and for now, we should get an empty console, as bellow:

and config:

For now, we don’t have only a lot in this configuration. Next step is to configure nodes. To configure node on localhost: java -jar selenium-server-standalone-3.3.1.jar -role node -hub

And now we can see our first node:

To override default configurations node, we can register the second node as fallows:

Listing below:

After refreshing console with nodes configuration we should have second with custom configuration:

How to write tests for Selenium Grid?

To design tests for the grid is not that complicated that you thing. But first od course we must create some changes in our code. Wery important is to import DesiredCapabilites package. This allows us to use: DesiredCapabilites object.

Define a browser and initialize a DesiredCapabilites object with firefox method:

Declare requirements for a specific platform and browser version.

For this configuration, we will run out tests for OSX with Firefox 52.0.2 browser.

Below is configuration for all platforms:


Packages in java

Java allows to a group class and organizes them into packages. Packages are very simple and useful mechanism to organize, easily locate files, reuse code, use libraries and also save time. In real life, there are situations when we can tray to create the class in the same name. This provides to namespace collisions. Packages also help to prevent that kind of problems.

How to use a package

The class can use all of the classes from their package and all of the public class from packages that belong to other pancakes. To get access to the public class from other packages we can do it in two ways:

  • Call a full name: com.somePackage myClass = new com.somePackage();

However, it’s not a very practical way. Easier and much faster way is to use keyword: import. This keyword allows for easier use of a class from another package.

Of course, we can import all class from the package by add *, for example:

Adding a class to the package

To add class to package first we must to add package name on the beginning of source file, for example:

If we don’t add package name, a class will be placed in a default package. This package doesn’t have a name.

Part of the program that is listed bellow describes that HelloController.java belongs to com.billingsystem.controller. Therefore file HelloController.java must be stored in com/billingsystem/controller:

Docker ~01 Docker and Raspberry Pi

Today I tried to install Docker on my Raspberry Pi 3 board to check how it will work, just for testing purpose. And you know what? It works very nice. First of all, I install Raspbinan Jessie Lite on SD card. For this point, I log in on a fresh installation and make the system update. After update list of repositories, I made the update of the whole raspberry:

Next step is to install Docker directly from the Docker website for ARM architecture.

This process will take a few minutes. After installation finished we will see the latest installation of Docker and that is running on ARM architecture:

Installation process suggests us to use user pi and add them to docker group. This will allow us to run docker command without using the sudo command.

To check that Docker demons are running we can use: sudo docker info

As you can see docker demons are running. After running classic: sudo docker run hello-world docker can’t find hello version:

The container didn’t start. This problem appears due to incompatible between two architectures: ARM and x86. To solve this problem the best way is to find Docker image that can be run on ARM architecture. So how can we find this image?

The best way is to find an image on Docker Hub. Searching for: ARM or RPI.

Another way is use Docker build to build our own Docker images for Raspberry. To create simple Dockerfile we must create the build directory, and in this folder placed Dockerfile that in my case contains:

To run Docker build: sudo docker build -t /rpi-java8 .
The build will take a while. After finish, we can check by using: sudo docker images. This will list:

To run created Docker image we can use: sudo docker run -it /rpi-java8. But this displayed all options for java because I didn’t specify anything. After adding some variables like: java -version we can see:

Using Travis CI

Getting started with Travis-Ci is pretty easy. First, we should create a .travis.yml file in root project directory. The second step is to create hooks between GitHub and Travis.

In my configuration of Travis, I used two operation systems: Windows and Linux. This configuration allows to runs each build in an isolated Google Compute Engine virtual machine that offer a vanilla build environment for each build. That allows creating clean slate and making clear output for our tests that runs in environment build from scratch every time.

Of course, this is some example of the initial setup for Travis, that I currently use for my pet project. In the near feature it will be updated for more components such as data store, environmental variables and adding APT Sources.

Travis will automatically create matrix environment variable with each Java version. In that case, all test will be run for every combination of three.

Eclipse IDE

Eclipse is an integrated development environment, a free platform widely distributed among Java developers, but also PHP, C ++. The last option especially highlights Visual Studio.

Why is writing about the Eclipse IDE? I’m writing about it because I started to develop my project seriously. Let’s get to know 2017 but IntellyJ Community version does not allow to create certain JEE components or use Spring Framework. That’s why I started looking for another solution and support for Spring. I choose Eclipse Neon. A few years ago I had quite a bit of tangency with this environment. It’s very powerful.

Installation is very simple. In the first step, we should primarily download versions from the eclipse.org project. Find the Downloads section and download Eclipse. I downloaded the Java Enterprise Edition (JEE). Installing such a package consists in extracting the * .zip archive to the appropriate folder. It depends primarily on our preferences and the operating system.

After the first start up location window should appear, in which we choose the workspace. This is the location where our projects will be stored. A perspective project is already ready for programming and the creation of the first project. We can also modify it with a simple drag and drop mechanism, dragging selected items into a convenient place for us, allowing partial personalization of the IDE perspective view.

On the left, we can see Package Explorer. The structure itself resembles a tree. On the right side, there is Outline, a quick preview of the class in the form of a sketch of the field and method, along with colored markings indicating the access specifiers. At the bottom, there is a box showing the errors, warnings, and problems that appear in his project. By default, the console also appears after launching the application.