I am new in Scala and I have to learn Scala and SBT, I read the sbt tutorial but i am unable to understand the use of sbt, for what purpose its been used.After reading this tutorial
I am still confused can any one will explain it in simple words, also suggest me if there is some tutorial for simple build tool
When you write small programs that consist of only one, or just two or three source files, then it's easy enough to compile those source files by typing scalac MyProgram.scala in the command line.
But when you start working on a bigger project with dozens or maybe even hundreds of source files, then it becomes too tedious to compile all those source files manually. You will then want to use a build tool to manage compiling all those source files.
sbt is such a tool. There are other tools too, some other well-known build tools that come from the Java world are Ant and Maven.
How it works is that you create a project file that describes what your project looks like; when you use sbt, this file will be called build.sbt. That file lists all the source files your project consists of, along with other information about your project. Sbt will read the file and then it knows what to do to compile the complete project.
Besides managing your project, some build tools, including sbt, can automatically manage dependencies for you. This means that if you need to use some libraries written by others, sbt can automatically download the right versions of those libraries and include them in your project for you.
Related
I have no Scala experience, but I need to create a JAR to include on a project's classpath from a single Scala source file.
I'm thinking there is a relatively straightforward way to do this, but I can't seem to figure it out.
The Scala file is here: http://pastebin.com/MYqjNkac
The JAR doesn't need to be executable, it just needs to be able to be referenced from another program.
The most convenient way is to use some build tool like Sbt or Maven. For maven there is the maven-scala-plugin plugin, and for Sbt here is a tutorial.
If you don't want to use any build tool, you may want to compile the code with scalac and then create the jar file manually by using zip on the resulting class files and renaming it to jar. But you have to preserve the directory structure. In your pastebin you use the package org.apache.spark.examples.pythonconverters, so make sure the directories match.
Btw, if you want to just integrate this piece of code with your java project, and using maven, you can have the scala code in your 1 project as well (in src/main/scala). Just use the maven-scala-plugin plugin and hook it to the compile phase, or some sooner phase if your Java code depends on it. However, I don't recommend mixing multiple languages in one project, I would split it into two separate ones.
I have a setup with 13 different eclipse projects (mostly scala and java). All projects have dependencies on each other in different ways. Now the project is starting to get big so we want to transition to a build tool and I wanted to try SBT.
First question: Is there any way to export the build files from eclipse? I mean, I have everything working in eclipse so It feels like an "export build.sbt" would be possible.
Second question: I have not found any easy way to add the project dependencies in a sbt file. Some sites say that I should publish all projects to a local maven repo and then using dependencies to be able to build it, but that requirement seems a little extreme.
I found my answers by a friendly person on the #sbt irc-channel.
For the first question: No, there seems to be none at the moment.
For the second qestion: I should create a multi-project build and define dependencies between projects that way (following the guide at: http://www.scala-sbt.org/release/docs/Getting-Started/Multi-Project.html)
I have recently completed the Scala course on Coursera, and since then I have been looking forward to getting my hands dirty with Scala again. I have written code for some years but I neither educated to be nor work as a programmer, so it took me a while to get a good opportunity but now that I have some time to invest and a good project to work on it's time...
Except I can't seem to get things set up properly, which I find really frustrating. I have OpenJDK 1.7.0_25 running on my Linux machine. I have downloaded and installed the Bundle Scala IDE build for Eclipse (just like we used in the course). And I got ScalaTest both as a jar file and the Eclipse plug-in.
I have a simple project (so far) and no matter what I do I can't seem to get my builds and tests in order. First off how exactly am I supposed to set up my project so that my classes and tests are actually run properly? All the assignments we got were projects that had the same structure, so do I have to have:
project
|--src
|--main
|--scala
|--test
|--scala
structure? If so why is it not the default way the project is setup when I create a new project? Do I create these folders manually, as packages or as source folders? The whole thing gets pretty murky..
I should mention that I tried to "Mavenize" the project using the contextual menu in Eclipse, added my ScalaTest dependency. The first thing that happens is that I get compile errors, at every point of dependency in my code. So clearly the library is not visible, in other words Maven does not seem to be doing much of management. I thought the whole point of Maven was to get and maintain dependencies as the project evolves. I concluded that I do not fully understand the way Maven works and thus I eventually gave up on Maven, once again, and went back to doing things manually.
Secondly, I can't seem to run my tests; the Run As... menu item does not include ScalaTest as it's mentioned in the documentation of ScalaTest Eclipse Plug-in. I have double checked that the plugin is installed. If I instead try to run using JUnitRunner then my tests are not recognized as valid tests. I have JUnit and ScalaTest on my build path, so it's got to be something else.
I suppose my overarching question is as follows:
given the Scala IDE build of Eclipse and ScalaTest, just exactly how am I supposed to set up my project (in Eclipse) so that I can just focus on writing my code and testing it, and hopefully not have any other headaches?
I work alone, and this project is not a product I need to deliver to some client. In other words I do not need to adhere to strict professionalism here. Honestly I just want to be able to code, get better acquainted with Scala and hopefully build a small data analysis tool that I will be using from time to time.
Thanks in advance!
Try using the sbt eclipse plugin:
https://github.com/typesafehub/sbteclipse
This is of course assumes that you use sbt as you build tool. If you don't at the moment you can find instructions on installation and usage here: http://www.scala-sbt.org/
Personally I've been using typesafe giter8 template (https://github.com/typesafehub/scala-sbt.g8) to setup my Scala projects, and then I use the sbt plugin mentioned above to generate eclipse project files.
Scala is somewhat Maven-based (sometimes implicitly), that's why you use that structure.
The easiest way I think is to create a simple Sbt/Maven POM and create the Eclipse project configurations (like with sbt eclipse). There you can set the dependencies (like the actual version of JUnit, Scalatest to use), so you can use the ScalaTest plugin easily.
In case of other issues, feel free to ask at the ScalaTest mailing list, Chee Seng and Bill Venners can help you a lot there.
The Scala IDE website has a full documentation on how to run unit testing frameworks with the IDE, have a look ! If you find missing elements, the bug tracker of the scala-IDE project is here.
I have developed a scala application for the first time, but I have to deploy it with a "one-click" type script that can run and build the scala application from source WITHOUT ECLIPSE.
Since I'm completely new to scala I don't know how to tell it where all my source files are etc... to get it to build my app from the command line. I also have 2 3rd party .jar libraries that I need to tell the scala compiler to link to...
Any documentation on this? Or example command lines? My project hierarchy is:
src/packagename: contains all .scala
bin/packagename: contains all.class files
libs/ -> contains 2 .jar files I will need to import somehow
I'm working on debian linux
EDIT: I found this ability to export in eclipse so I created a .java file and called my main scala object from it. Then I exported as a runnable jar. However, when I go to run the new runnable jar "sudo java runnable.jar" it says "class not found exception: runnable.jar"
You should take a look at https://github.com/harrah/xsbt/wiki which is the common way to build a Scala project. Run through the tutorial in the wiki to learn how you should organise your directory structure, so that everything may run fine.
If you want to combine it with eclipse, checkout this plugin: https://github.com/typesafehub/sbteclipse
This question is not limited to lex and yacc, but how can I add a custom script compiler as part of a project? For example, I have the following files in the project:
grammar.y
grammar.l
test.script
The binary 'script_compiler' will be generated using grammar.y and grammar.l compiled by lex, yacc and g++. And then I want to use that generated script_compiler to compile test.script to generate CompiledScript.java. This file should be compiled along with the rest of the java files in the project. This setting is possible with XCode or make, but is it also possible with Eclipse alone? If not, how about together with Maven plugin?
(I might setup the script compiler as a separate project, but it would be nice if they can be put in the same project so that changes to the grammar files can be applied immediately)
Thanks in advance for your help!
You can add a custom "Builder" from the project properties dialog. This can be an ant script (with an optional target) or any other script or executable.
There are also maven plugins for ant and other scripting languages
If you just want to run an external program in Maven this is what you want: http://mojo.codehaus.org/exec-maven-plugin/ -- you can then run Maven targets from your IDE or command line and it should do the right thing either way.
To integrate with the normal compilation bind the plugin to the "generate-sources" phase and add the location where the Java files are generated to the "sourceRoot" option of the exec plugin. That way the compiler will pick them up.
Ideally you generate the code into a folder "target/generated-sources/MY_SCRIPT_NAME". That is the standard location for generated sources in the Maven world and e.g. IntelliJ IDEA will pick up source files inside of that location. Note that this doesn't work if the files are directly in "target/generated-sources".
The other option is to write your own Maven plugin, which is actually quite easy as well. See e.g. https://github.com/peterbecker/maven-code-generator