Jenkins 2.2 it is throwing the exception:

org.jenkinsci.plugins.scriptsecurity.sandbox.RejectedAccessException: Scripts not permitted to use method groovy.lang.GroovyObject invokeMethod java.lang.String java.lang.Object (org.codehaus.groovy.runtime.GStringImpl call org.codehaus.groovy.runtime.GStringImpl)
at org.jenkinsci.plugins.scriptsecurity.sandbox.whitelists.StaticWhitelist.rejectMethod(StaticWhitelist.java:165)
at org.jenkinsci.plugins.scriptsecurity.sandbox.groovy.SandboxInterceptor.onMethodCall(SandboxInterceptor.java:117)
at org.jenkinsci.plugins.scriptsecurity.sandbox.groovy.SandboxInterceptor.onMethodCall(SandboxInterceptor.java:103)
at org.kohsuke.groovy.sandbox.impl.Checker$1.call(Checker.java:149)
at org.kohsuke.groovy.sandbox.impl.Checker.checkedCall(Checker.java:146)
at com.cloudbees.groovy.cps.sandbox.SandboxInvoker.methodCall(SandboxInvoker.java:15)
at WorkflowScript.run(WorkflowScript:71)
at __cps.transform__(Native Method)
at com.cloudbees.groovy.cps.impl.ContinuationGroup.methodCall(ContinuationGroup.java:55)
at com.cloudbees.groovy.cps.impl.FunctionCallBlock$ContinuationImpl.dispatchOrArg(FunctionCallBlock.java:106)
at com.cloudbees.groovy.cps.impl.FunctionCallBlock$ContinuationImpl.fixArg(FunctionCallBlock.java:79)
at sun.reflect.GeneratedMethodAccessor408.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:601)
at com.cloudbees.groovy.cps.impl.ContinuationPtr$ContinuationImpl.receive(ContinuationPtr.java:72)
at com.cloudbees.groovy.cps.impl.FunctionCallBlock$ContinuationImpl.dispatchOrArg(FunctionCallBlock.java:100)
at com.cloudbees.groovy.cps.impl.FunctionCallBlock$ContinuationImpl.fixArg(FunctionCallBlock.java:79)
at sun.reflect.GeneratedMethodAccessor408.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:601)
at com.cloudbees.groovy.cps.impl.ContinuationPtr$ContinuationImpl.receive(ContinuationPtr.java:72)
at com.cloudbees.groovy.cps.impl.ContinuationGroup.methodCall(ContinuationGroup.java:57)
at com.cloudbees.groovy.cps.impl.FunctionCallBlock$ContinuationImpl.dispatchOrArg(FunctionCallBlock.java:106)
at com.cloudbees.groovy.cps.impl.FunctionCallBlock$ContinuationImpl.fixArg(FunctionCallBlock.java:79)
at sun.reflect.GeneratedMethodAccessor408.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:601)
at com.cloudbees.groovy.cps.impl.ContinuationPtr$ContinuationImpl.receive(ContinuationPtr.java:72)
at com.cloudbees.groovy.cps.impl.ConstantBlock.eval(ConstantBlock.java:21)
at com.cloudbees.groovy.cps.Next.step(Next.java:58)
at com.cloudbees.groovy.cps.Continuable.run0(Continuable.java:154)
at org.jenkinsci.plugins.workflow.cps.SandboxContinuable.access$001(SandboxContinuable.java:19)
at org.jenkinsci.plugins.workflow.cps.SandboxContinuable$1.call(SandboxContinuable.java:33)
at org.jenkinsci.plugins.workflow.cps.SandboxContinuable$1.call(SandboxContinuable.java:30)
at org.jenkinsci.plugins.scriptsecurity.sandbox.groovy.GroovySandbox.runInSandbox(GroovySandbox.java:108)
at org.jenkinsci.plugins.workflow.cps.SandboxContinuable.run0(SandboxContinuable.java:30)
at org.jenkinsci.plugins.workflow.cps.CpsThread.runNextChunk(CpsThread.java:164)
at org.jenkinsci.plugins.workflow.cps.CpsThreadGroup.run(CpsThreadGroup.java:277)
at org.jenkinsci.plugins.workflow.cps.CpsThreadGroup.access$000(CpsThreadGroup.java:77)
at org.jenkinsci.plugins.workflow.cps.CpsThreadGroup$2.call(CpsThreadGroup.java:186)
at org.jenkinsci.plugins.workflow.cps.CpsThreadGroup$2.call(CpsThreadGroup.java:184)
at org.jenkinsci.plugins.workflow.cps.CpsVmExecutorService$2.call(CpsVmExecutorService.java:47)
at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:334)
at java.util.concurrent.FutureTask.run(FutureTask.java:166)
at hudson.remoting.SingleLaneExecutorService$1.run(SingleLaneExecutorService.java:112)
at jenkins.util.ContextResettingExecutorService$1.run(ContextResettingExecutorService.java:28)
at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:471)
at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:334)
at java.util.concurrent.FutureTask.run(FutureTask.java:166)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
at java.lang.Thread.run(Thread.java:722)

What I did:

def version() {
String path = pwd();
def matcher = readFile("${path}/pom.xml") =~ '<version>(.+)</version>'
return matcher ? matcher[0][1] : null
}

I am triying to adquired the version from a pom.xml file, the code it is based in:

https://github.com/jenkinsci/pipeline-plugin/blob/master/TUTORIAL.md

My software specification:

Jenkins 2.2

Pipeline plugins: