我有以下手动工作区清理，所以正如你提到的，它应该工作，以及检查下面。
我假设您可能没有正确获取文件路径

//load jobs
def jobs = Jenkins.instance.getAllItems(Job.class)

//iterate over
for(job in jobs) {

//seems like they dont have workspace
  if(job instanceof hudson.model.ExternalJob){
    continue
  }

     String workspace = null

     //pipelines dont have workspace
     if(job instanceof org.jenkinsci.plugins.workflow.job.WorkflowJob){
       println ("workflow job, not cleaning")   
       continue
     }

     try{
       workspace = job.workspace
     }catch(Exception e){
         //already clean eg.
       println ("no workspace, not cleaning")   
       workspace = null
     }

     if(workspace != null){
       //creation of the workspace and modules folder
       //again not sure, but sometimes was failing due boolean ..
       if(workspace instanceof java.lang.Boolean){
        println "cant cleanup"
        continue
       }

       File folder = new File(workspace) 

       //Check if the Workspace folder really exists
       if(folder!=null && folder.exists()){ 
         //workspace cleanup

         //get files
         File[] files = null
         try{
          files=new File(workspace).listFiles().sort(){
             //println it.name  

             if(!it.isFile()){
               it.deleteDir()
             }else{
               it.delete()
             }
           }
         }catch(Exception e){
            println "cant clean: " + workspace          
         } 

       }else{
        println "workspace is not existing, not cleaning"
       }  
   }
}

所以，清理工作的核心是：

//get files
         File[] files = null
         try{
          files=new File(workspace).listFiles().sort(){
             //println it.name  

             if(!it.isFile()){
               it.deleteDir()
             }else{
               it.delete()
             }
           }
         }catch(Exception e){
            println "cant clean: " + workspace          
         }