Invalid payload - Slack API JSON

I am using a Groovy script to send a POST using the Slack API, at present I am getting invalid_payload returned and I think this is most likely due to the formatting of my JSON. I know the Slack API expects it JSON with double quotes but I can't seem to be able to pass a variable into the JSON object:

SUCCESS_MESSAGE = '{"attachments": [{"color": "#2A9B3A", "author_name": ${DEV_NAME}, "title": "Build Status", "title_link": ${BUILD_URL}, "text": "Successful Build" }]}'
def response = ["curl", "-X", "POST", "-H", "Content-Type: application/json", "-d", "${SUCCESS_MESSAGE}", "https://hooks.slack.com/services/${SLACK_WEBHOOK}"].execute().text

How should I correctly format my SUCCESS_MESSAGE var so I don't get the error?

Solution

You need to quote your DEV_NAME and BUILD_URL variable expansions so the JSON string is valid.
Your whole string needs to be enclosed in " instead of ' so the variables are actually expanded
And you need to escape the " inside your string so they appear in your JSON string.

SUCCESS_MESSAGE = "{\"attachments\": [{\"color\": \"#2A9B3A\", \"author_name\": \"${DEV_NAME}\", \"title\": \"Build Status\", \"title_link\": \"${BUILD_URL}\", \"text\": \"Successful Build\" }]}"`

Alternatively you can generate the JSON in much nicer programmatic way. Which would be helpful if your notifications got a bit more complicated:

def notification = [
  attachments: [
    [
      color: "#2A9B3A",
      author_name: DEV_NAME,
      title: "Build Status",
      title_link: BUILD_URL,
      text: "Successful Build"
    ]
  ]
]

def response = ["curl", "-X", "POST", "-H", "Content-Type: application/json", "-d", JsonOutput.toJson(notification), "https://hooks.slack.com/services/${SLACK_WEBHOOK}"].execute().text