AWS CloudFormation Error: !Join object requires two parameters, (1) a string delimiter and (2) a lis-CodePudding

I'm getting an error in CloudFormation using the !Join function:

Template error: every Fn::Join object requires two parameters, (1) a string delimiter and (2) a list of strings to be joined or a function that returns a list of strings (such as Fn::GetAZs) to be joined.

My Code:

  RDSSubnetGroup:
    Type: AWS::RDS::DBSubnetGroup
    Condition: CreationRDS
    Properties:
       DBSubnetGroupDescription: !Ref RDSName
       SubnetIds: !Ref SubnetIds
  
  RDSAuroraServerless:
    Type: AWS::RDS::DBCluster
    Condition: CreationRDS
    Properties:
      Engine: aurora-mysql
      EngineMode: serverless
      EngineVersion: !Ref EngineVersion
      DatabaseName: !Ref RDSName
      MasterUsername: admin
      MasterUserPassword: !Ref MasterUserPassword
      DBClusterIdentifier: !Ref RDSName
      ScalingConfiguration:
        MinCapacity: 1
        MaxCapacity: 2
        SecondsUntilAutoPause: 300
      BackupRetentionPeriod: 7
      DeletionProtection: false
      VpcSecurityGroupIds:
        - !Ref SecurityGroup
      DBSubnetGroupName: !Ref RDSSubnetGroup

Outputs:
  JDBCOutput:
    Condition: CreationRDS
    Value: 
      !Join [ '', [!GetAtt RDSAuroraServerless.Endpoint.Address, /, !Ref RDSName] ]

Can you help me and show me where I'm going wrong?

CodePudding user response：

Based on the comments.

The Join statement in the question is correct. Upon further investigation, the OP found the problem in other Join (not shown in the question), which lead to solution.