spring.profiles is not working as expected in spring boot - spring-boot

Question

boot config *.yml file.
server.port: 2222
spring:
application:
name: x-service
data:
mongodb:
host: db.x
database: x
# userName: ${db.userName}
# password: ${db.password}
rabbitmq:
# port: ${queue.port}
host: queue.x
username: ${queue.userName}
password: ${queue.password}
listener:
max-concurrency: 1
prefetch: 1
acknowledge-mode: auto
auto-startup: true
dynamic: true
###########DEV##############
spring.profiles: dev
#queue.virtual.host: xuser
queue.userName: guest
queue.password: guest
queue.port: 5672
#db.userName:
#db.password:
falconUrl: http://x.y.com
##########DEFAULT###########
spring.profiles: qa
queue.virtual.host: xuser
queue.userName: xuser
queue.password: xpassword
queue.port: 3456
db.userName: xuser
db.password: xpassword
falconUrl: http://x.z.com
It gives me org.yaml.snakeyaml.parser.ParserException: while parsing MappingNode
in 'reader', line 1, column 1:
server.port: 2222
^
Duplicate key: spring.profiles
in 'reader', line 47, column 1:
error. If I comment properties of one of the profile.It works fine.
Can anyone please suggest what is wrong here?

Answer 1

The error message is actually quite specific and accurate: in the top-level mapping of your YAML file (the one starting with the key-value pair server.port and 2222 you have two identical keys (the scalar spring.profiles). And duplicate keys are not allowed in YAML, as the are required to be unique according to the specification.
The underlying problem is that if you want to change the configuration depending on the environment, you'll have to follow the documented specification, which states that:
A YAML file is actually a sequence of documents separated by --- lines, and each document is parsed separately to a flattened map.
If a YAML document contains a spring.profiles key, then the profiles value (comma-separated list of profiles) is fed into the Spring Environment.acceptsProfiles() and if any of those profiles is active that document is included in the final merge (otherwise not)
Your YAML file is a single implicit YAML document because it lacks the directive indicator --- that occurs at the beginning of an explicit YAML document. (the YAML directive ... that indicates end-of-document might not be supported properly supported by snake-yaml, at least it is not mentioned in the examples).
Your code should look like:
server.port: 2222
spring:
application:
name: x-service
data:
mongodb:
host: db.x
database: x
# userName: ${db.userName}
# password: ${db.password}
rabbitmq:
# port: ${queue.port}
host: queue.x
username: ${queue.userName}
password: ${queue.password}
listener:
max-concurrency: 1
prefetch: 1
acknowledge-mode: auto
auto-startup: true
dynamic: true
###########DEV##############
---
spring.profiles: dev
#queue.virtual.host: xuser
queue.userName: guest
queue.password: guest
queue.port: 5672
#db.userName:
#db.password:
falconUrl: http://x.y.com
##########DEFAULT###########
---
spring.profiles: qa
queue.virtual.host: xuser
queue.userName: xuser
queue.password: xpassword
queue.port: 3456
db.userName: xuser
db.password: xpassword
falconUrl: http://x.z.com
The statement in the documentation that "each document is parsed separately to a flattened map" is of course only true, if each of the documents has a mapping at the top level. That is what spring-boot expects, but you can as easily have a scalar or sequence at the top level of a document, and such documents are certainly not parsed by snake-yaml to a flattened map.