while iam uploading artifacts through jenkins file it throwing this error if any one knows it please revert it

this is the error iam facing

server = Artifactory.server 'Artifactory'

def uploadSpec = """{
    "files": [
    {
    "pattern": "**/target/*.war",
    "target": "releases/${APP_REPO}/${version.trim()}/"
    }
    ]}"""
server.upload(uploadSpec)

this is the syntax iam following