How to pass a json object as string to a variable

Ramesh Ramalingam

This question is in reference to Atlassian Documentation: Variables for deployment environments

Ask your question here...

Steffen Opel [Utoolity]

Update

Bamboo does not parse variable content in any way, i.e. the content is always just a string. The problem you are encountering is passing a JSON string as a parameter to AWS CloudFormation via the AWS CloudFormation Stack task, which expects those parameters to be passed into the Parameters field as a JSON string in turn, e.g.:

[
  {
    "ParameterKey": "LambdaPolicy",
    "ParameterValue": "${bamboo.lambda.LambdaPolicy}"
  }
]

When ${bamboo.lambda.LambdaPolicy} contains just the original JSON, the resulting nested JSON is invalid and triggers the encountered MalformedJsonException.

In order to pass a JSON string inside another JSON string in such a scenario, you need to escape it (e.g. manually via JSON Escape/Unescape).

Example

Given your example JSON input:

{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Effect": "Allow",
      "Action": [
        "logs:CreateLogGroup",
        "logs:CreateLogStream",
        "logs:PutLogEvents"
      ],
      "Resource": "arn:aws:logs:*:*:*"
    },
    {
      "Effect": "Allow",
      "Action": [
        "apigateway:*"
      ],
      "Resource": "*"
    },
    {
      "Effect": "Allow",
      "Action": [
        "iam:PassRole",
        "iam:GetServerCertificate"
      ],
      "Resource": "*"
    }
  ]
}

You would need to pass the following escaped JSON string instead (i.e. as the value of ${bamboo.lambda.LambdaPolicy} in your scenario):

{\n  \"Version\": \"2012-10-17\",\n  \"Statement\": [\n    {\n      \"Effect\": \"Allow\",\n      \"Action\": [\n        \"logs:CreateLogGroup\",\n        \"logs:CreateLogStream\",\n        \"logs:PutLogEvents\"\n      ],\n      \"Resource\": \"arn:aws:logs:*:*:*\"\n    },\n    {\n      \"Effect\": \"Allow\",\n      \"Action\": [\n        \"apigateway:*\"\n      ],\n      \"Resource\": \"*\"\n    },\n    {\n      \"Effect\": \"Allow\",\n      \"Action\": [\n        \"iam:PassRole\",\n        \"iam:GetServerCertificate\"\n      ],\n      \"Resource\": \"*\"\n    }\n  ]\n}

This will yield the same results as passing the unescaped JSON via the AWS Management Console, where the problem does not exist due to its more advanced UI, which accepts each parameter via an individual text input field.

Here's the corresponding Bamboo log output for a variable:

Substituting variable: ${bamboo.lambda.LambdaPolicy} with {
  \"Version\": \"2012-10-17\",
  \"Statement\": [
    {
      \"Effect\": \"Allow\",
      \"Action\": [
        \"logs:CreateLogGroup\",
        \"logs:CreateLogStream\",
        \"logs:PutLogEvents\"
      ],
      \"Resource\": \"arn:aws:logs:*:*:*\"
    },
    {
      \"Effect\": \"Allow\",
      \"Action\": [
        \"apigateway:*\"
      ],
      \"Resource\": \"*\"
    },
    {
      \"Effect\": \"Allow\",
      \"Action\": [
        \"iam:PassRole\",
        \"iam:GetServerCertificate\"
      ],
      \"Resource\": \"*\"
    }
  ]
}

And here's the resulting Bamboo log output after the variable has been used inside the Parameters field:

... bamboo.custom.aws.cfn.stack.resources.tst-1-TST-AWSB-CFNPJ-21-2.parameters.LambdaPolicy: {  "Version": "2012-10-17",  "Statement": [    {      "Effect": "Allow",      "Action": [        "logs:CreateLogGroup",        "logs:CreateLogStream",        "logs:PutLogEvents"      ],      "Resource": "arn:aws:logs:*:*:*"    },    {      "Effect": "Allow",      "Action": [        "apigateway:*"      ],      "Resource": "*"    },    {      "Effect": "Allow",      "Action": [        "iam:PassRole",        "iam:GetServerCertificate"      ],      "Resource": "*"    }  ]}

In other words, the escaped JSON input properly ends up in CloudFormation as an unescaped JSON parameter.

Usability Improvements

I realize that this escaping requirement poses a notable usability issue (the Parameters field inline dialog examples have a a small hint that "Reserved JSON characters in Bamboo variable content need to be escaped at runtime", however, it had been missing in the task documentation, and either way this is not easily discovered). I've filed UAA-203 to contemplate how to improve the usability in this regard (suggestions welcome).

 

---

Initial Answer

We have outlined a more generic solution for Utoolity's Bamboo add-ons in our KB article How to supply task input from an external source like a file - here's a slightly adjusted version for your JSON use case:

Step-by-step guide

You want to inject a JSON object into a Bamboo variable:

1. Add the steps/tasks to provide the JSON object as a file, e.g. by downloading a shared artifact, checking it out from a source code repository or fetching the content from an URL with a script (the example uses the cloudformation.parameters.json Bitbucket snippet).
   
   
2. Install the Variable tasks for Bamboo add-on (still works in Bamboo 5.12, just go to 'Manage add-ons' and upload it manually).
3. Add a Variable File reader task to Get the full content of a file and inject it in a variable.
   
   
   
   1. Specify a variable name, e.g. cloudformation.parameters.
      1.  Bamboo adds the prefix bamboo, so this variable needs to be referenced as ${bamboo.cloudformation.parameters}.
   2. Specify the file provided in step 1. to read the content from.
      1. Local scope is sufficient for reusing the variable inside the same job. Read the inline help for details on Result or Plan/Deployment scoped variables.
4. Reference the variable from a subsequent task to access the contained JSON, e.g. place ${bamboo.cloudformation.parameters} into a task's input field.
   
   

Limitation

This workaround has the limitation that the included content cannot use Bamboo variables in turn, because Bamboo doesn't yet support nested/recursive expansion of variables - see https://jira.atlassian.com/browse/BAM-8266.