play framework unable to run an existing project

Question

I'm a rookie developer trying to run an application using play framework. I've followed the tutorial and can successfully create a new project.

However when I go to the directory that has the project I'm supposed to work on and enter the play command I get the following error:

[error] Not a valid command: play (similar: last, alias, loadp)
[error] Not a valid project ID: play
[error] Not a valid configuration: play
[error] Not a valid key: play (similar: clean)
[error] play

I have very little knowledge regarding the framework and don't know where to start correcting my mistake. Any suggestions ?

Answer 1

You have to run the play command this way:

./play cmd [app_path] [--options]

where in case of running a project, it is

./play run /path/to/projectname

Answer 2

I am facing this problem in the context of sub projects.

This is what worked for me.

---

Code:

import sbt._
import sbt.Keys._

object ApplicationBuild extends Build {

  val helloWorldProj = Project(id = "HelloWorld", base = file("helloworld"))    

  val appName = "WebApp"
  val appVersion = "1.0"
  val appDependencies = Seq()

  val webAppProj = PlayProject( appName, appVersion, appDependencies, path = file("webapp"), mainLang = PlayProject.SCALA)
    .dependsOn(helloWorldProj)
    .aggregate(helloWorldProj)

}

On running the play command, I get the following error:

Error:

[info] Set current project to HelloWorld (in build file:/D:/EclipseProjects/HelloWorldPlayMultiProject/)
[error] Not a valid command: play (similar: last, alias, loadp)
[error] Not a valid project ID: play
[error] Not a valid configuration: play
[error] Not a valid key: play (similar: play-hash, play-dist, play-conf)
[error] play
[error]     ^

Solution:

Now, if I rename helloWorldProj as zhelloWorldProj , it works! In this case, play sets the active project to WebApp .(Since webAppProj variable name alphabetically comes before zhelloWorldProj )

I can then change the active project to HelloWorld by giving the command project HelloWorld .

I think this has something to do with how sbt finds the Project objects using reflection.

Answer 3

I delete all directories in the project folder and it works. Do not delete files (build.properties, Build.scala and plugins.sbt)

Answer 4

需要有关于你的环境（操作系统，播放版本等）的更多细节，但是如果你得到的错误是游戏不是一个有效的命令，我的第一个行动方案是检查play.sh的路径（我假设你是使用非Windows）包含在您的系统路径中？

Answer 5

The problem was the version difference of play. The project I was suppose to work on was developed in play 1.2 where as I installed the version 2.0 .

By the way, working with 2.0 on a project developed by version 1.2 is possible, but I strongly recommend not to do it that way as there are problems on the later stages as well.

Answer 6

Depending on the language you're using, make sure one of the following is in your build.sbt file:
play.Project.playJavaSettings
play.Project.playScalaSettings

Answer 7

I also got the same problem! What happened was in my /user/xxx/project folder there were old projects from 1.x version. Deleting that folder worked for me!