Gradle and Command Line Workshop Activity

Transcription

1 Gradle and Command Line Workshop Activity Activity for the SUNY Oswego Computer Science Association s Gradle and Command Line Workshop. Written by Christopher Wells, and released under CC0 license. Introduction In this workshop we will be going over how to use Gradle and the Linux command line. Will try out a few Linux commands to learn what they do and when to use them, and learn how to use Gradle to compile and run some Java programs. For this workshop we will be working on the CS servers, so be sure to install an FTP client such as Filezilla, this will allow you to send files to and from the servers. Also if you are using Windows, then you should install PuTTy, which is a program that will allow you to remotely use the department s Linux servers from anywhere in the world. Connecting to the Servers In this workshop we will be using the department s Linux servers to get familiar with the command line and Gradle. Using the servers will make this easier as we: Won t need to install Gradle (which can be tricky) Will be able to use Linux command line utilities (which come in handy) Using the servers and the command line can take a little while to get used to, but it can be a huge time saver in the long run. Remotely connecting to the servers is called SSH-ing. This stands for Secure SHell Protocol, where shell refers to the command line. Connecting to the servers will differ a bit based on what operating system you are using. Mac + Linux If you are using Mac or Linux you can open up the terminal and run the following command. ssh YOUR_USERNAME@pi. cs. oswego. edu For example if your username is jdoe42 then you would run the following command.

2 ssh cs. oswego. edu Windows If you are using Windows, run PuTTY. Put in the following settings and click Open at the bottom of the window. Host Name: * If you are prompted about an RSA key type yes How to use the Command Line The command line (or terminal) is a text-based interface for interacting with a computer. It allows you to input commands to perform various functions as opposed to performing them with a graphical (GUI) application. Using the command line can make it easier to perform actions in a simple text commands that would be difficult to perform in a GUI application, such as processing a large amount of files. There are a few important concepts to keep in mind while using the command line. Path The path is your current location in your file system. When you are using the command line, you are always in a specific directory (folder). By default you start in your home directory /home/username also referred to by ~, but you can navigate up and down into other directories. You can find out what your current path is by looking at the command line prompt or by running the pwd command. pi:~/git> ^ \ This is your path cd Command In order to change the path, you can use the cd (change directory) command. When running the cd command you must specify the directory that you want to move into. cd my_code Enter the my_code directory

3 cd my_code/hw01 cd.. cd../.. cd /home/cwells2/public_html/ Enter the hw01 directory inside the my_code directory Move up one directory Move up two directories Move into the /home/cwells2/public_html/ directory. This is known as cd-ing into an absolute path Try playing around with the cd command a bit. Try moving into and out of a few different directories until you get the hang of it. ls Command In order to see what files are in the current directory you can use the ls (list) command. This will simply print out a list of the files in the current directory so that you can see what files you can work with. You can also supply some command flags (options) to change the information the command gives you. ls ls -a ls -l ls -la Lists the files in the current directory Includes all hidden files. Gives more detailed file information Command flags can be chained like this to combine their functionality Try running the ls commands with some of the options above to get the hang of it. ls is a very handy command that you will use all the time. File Editing To edit a file on the server, you can use one of a number of different text editors. Command line text editors can be a little bit tricky to use at first, but can be very powerful once you get used to them. Two commonly used text editors are: Vim Emacs

4 Both editors have very similar functionality, but differ in the keybindings that they use to perform different actions. Usually people pick one to the two and stick with it. I would recommend taking a look at some video tutorials online to learn how to use one of these editors. Though for now all you need to know is how to edit text in them as well as how to save and quit. vim file.txt emacs file.txt Opens file.txt in Vim Opens file.txt in Emacs Vim Type i to enter Insert Mode Edit your file Type Esc :wq Enter to save and exit Emacs Edit your file Type Ctrl + x Ctrl + c to save and exit Using Gradle Gradle is a type of program called a build tool. Build tools allow you to compile and run your programs on the command line without having to directly run the compiler on all of your code with all of the configuration options you need. They also allow you to easily use external libraries in your code. In order to use Gradle for a Java project, you need to setup your code in a specific directory structure and create a Gradle configuration file called a build.gradle file. Project Structure The directory structure of a Gradle project should be setup in the following manner. project_directory build.gradle src main java mypackage Main.java Cube.java Room.java

5 In the project directory (ex. csc241hw01) you should have your Gradle config file build.gradle, which will tell Gradle how your project is set up, what libraries and plugins you want to use, and other miscellaneous compilation settings. In the project directory you should also have the nested directories src/main/java/mypackage. These directories serve the following purposes: src main java mypackage Contains all of the source code subdirectories Contains all of the subdirectories with source code for the program main Contains the Java packages Contains the source code for the program s java package This directory structure can seem overkill at first, but it comes in handy if you want to add tests for your code or source code in other JVM languages like Scala, which is made easier though adding additional directories which fit the project structure. (ex. src/test/scala/mypackage ) Build Configuration Once you setup the structure of your project and add some Java files, including a main class, you can start working on creating the build.gradle config file. The first thing you need in your Gradle config file is the list of Gradle plugins that you would like to use. Some good ones to use are java which lets you compile Java files, application which gives you the gradle run command, and errorprone which gives you some useful warning messages. plugins { id 'java' id 'application' id 'net.ltgt.errorprone' version '0.0.13' } Next, if you have a main class, then you will want to specify which class is the main class, you can do this in the following manner, substituting in the correct class name and package. mainclassname = "mypackage.main" Finally, if you are using errorprone then you will need to include the following lines to tell Gradle where it can download the plugin from.

6 repositories { mavencentral () } Compiling and Running Once you have setup the correct project structure and written the configuration file, you can now use Gradle to compile and run your project. To simply compile your project you can run the following command in the top directory of the project. gradle build This will compile all of the.java files, creating.class files for each (in build/classes/main/mypackage ) and a jar file for the project (in build/libs/ ). If you include the application plugin in the build.gradle file, then you can compile and run your program by using the following command. gradle run