Unsupported major.minor version 51.0 while running play framework

Question

I know there is version conflict. Just want someone to tell me how to resolve it. In previous stackoverflow post no one tells the solution.

Versions: Ubuntu: 12.04.1 LTS

Answer 1

On Ubuntu to change Java version for both compiling and running you need to call:

sudo update-alternatives --config javac 

and

sudo update-alternatives --config java

Answer 2

You are using different JDK versions to compile and run the application. You say that:

java: 1.6.0_24 (OpenJDK) 
javac: 1.7.0_07 (OpenJDK)

So your compiler (javac) is a newer release than the java command, which means the second can't run your compiled files. You must use only 1 version of the JDK (same for java and javac)

Answer 3

A better solution is to change the target version, so you could compile to 1.6 from 1.7 like this: How can I set the javac compile version for Play Framework 2.0 to prevent "Unsupported major.minor version"?

Put this in your Build.scala:

val main = play.Project(appName, appVersion, appDependencies).settings(
  // Force compilation in java 1.6
  javacOptions in Compile ++= Seq("-source", "1.6", "-target", "1.6")
)