Getting ClassNotFoundException in Grails 2.5.6 - grails

Question

Migrating from 1.3.7 to 2.5.6
java.lang.ClassNotFoundException: org.codehaus.groovy.grails.project.compiler.GrailsProjectCompiler how can we fix this?
Trying to build project using goal grails:clean grails:war -Dmaven.skip.test=true
Grails Version : 2.5.6
Java version 1.7

Answer 1

As stated by the comments, you're in for quite a ride to get this up and running.
This particular error is probably because you are missing the new dependencies needed for Grails. This is what you need if you have a maven project which I assume you have while getting this problem:
<dependency>
<groupId>org.grails</groupId>
<artifactId>grails-dependencies</artifactId>
<version>${grails.version}</version>
<type>pom</type>
</dependency>
<dependency>
<groupId>org.grails</groupId>
<artifactId>grails-test</artifactId>
<version>${grails.version}</version>
<scope>test</scope>
</dependency>
<dependency>
<groupId>org.grails</groupId>
<artifactId>grails-plugin-testing</artifactId>
<version>${grails.version}</version>
<scope>test</scope>
</dependency>
You also have to remove all of the old dependencies to the 1.3 grails core. In 1.3 it was a series of dependencies if I don't remember incorrectly.
If it is not a maven project you should get this for free by specifying the inerits("global") in your BuildConfig.groovy:
grails.project.dependency.resolution = {
// inherit Grails' default dependencies
inherits("global") {
// specify dependency exclusions here; for example, uncomment this to
}
...
That said, this will not be the last of your problems while upgrading. I have successfully managed to upgrade some small projects but it has taken quite an effort. For larger projects, I would seriously consider if it is worth it.
My best advice if you decide to go through with it is to generate a new empty 2.5.6 project and compare settings and dependencies to your legacy project.