Scala和Eclipse：导出为Jar文件，但找不到主要方法

Question

I have a problem exporting a scala project as a .jar file and then run it using a command in the cmd. The file takes a port number as its parameter, because it establishes a TCP connection between a server and a client. There are three files:

• Engine.scala = object containing the main method: Starts a web server (waits for input query from a html file and transfers it to a text processing server) and a text processing server (this will take the query and search an inverted index of a text file (alice in wonderland ;) and return all the lines of the text file, in which the query terms occur).

• TextProcessingServer: does the query search

• WebServer: waits for query input

When I start it in eclipse and pass a port number (8090 in my case), everything works fine and I can query my server using a web site.

However, if I try to export it, it doesn't work anymore. To export it to a jar, I do the following:

1. in eclipse, I export it by: Export -> Java -> JAR File -> 1234.jar and check "Export all output folders for checked projects" and "Export Java source files and resources".

2. In the command line, I type: java -cp 1234.jar:lib/scala-library.jar assignment1.Engine 8090

Now I get the following error message:

Error: Could not find or load main class assignment1.Engine

Versions used:

Scala IDE build of Eclipse SDK (Version Indigo)

Build id: 3.0.1-vfinal-20130718-1727-Typesafe

Can anybody help me? I have tried almost everything suggested on the internet, like adapting the Manifest etc. but nothing seems to work. It will just not find the main method :(

What I already noticed when I run it in Eclipse is that I cannot choose "run as Scala application", I can only run it as Java application. Don't know if that is of any importance...

Thanks a lot for your help!

Answer 1

You're from Distributed Systems HS2013, right? :-D

The problem is, that in the command line you're typing lib/scala-library.jar but you're not providing the scala library in the same folder as your jar is in. If your jar is on the Desktop you need to copy the folder lib from your scala installation to the Desktop or you just provide the scala-library.jar (than you type scala-library.jar instead of lib/scala-library.jar ). If you're using Windows you should replace the : with a ; so it looks like this:

java -cp 1234.jar;lib/scala-library.jar assignment1.Engine 8090

It will probably not find your text file though, so you have to copy it to the same folder (eg Desktop) as well.