can not access environment variable specified by user provided service with java - cloud-foundry

Question

I have created a user provided service as follows:
cf cups myservice -p '{"db": "text"}'
and I bind this service to my app, the service name is myservice.
When i use cf env command, i can see the message:
"user-provided": [{
"credentials":{
"db":"text"
},
"name":"myservice"
}]
but when i access this variable with java
System.getenv("cloud.services.myservice.db")
is null. Why can't I access the db value?

Answer 1

When you do cf env on your app, you see an environment variable named VCAP_SERVICES that contains a JSON data structure like you showed:
VCAP_SERVICES: {
"user-provided": [
{
"credentials":{ "db":"text" },
"name":"myservice"
}
]
}
Your application can retrieve this JSON structure with System.getenv("VCAP_SERVICES"). You can then parse the JSON returned from that call into a Map, for example, and retrieve the values needed.
There is no environment variable available to your app named cloud.services.myservice.db, so System.getenv("cloud.services.myservice.db") won't return anything useful.
Spring Boot parses the VCAP_SERVICES environment variable and creates Spring environment properties like cloud.services.myservice.credentials.db and vcap.services.myservice.credentials.db. These properties can't be retrieved with System.getenv() because they exist only in the Spring environment abstraction, not in the OS environment. This is described nicely in a Spring blog post. More details are in the Spring Boot javadoc.

Answer 2

Services In CloudFoundry are presented JSON blob in the VCAP_SERVICES environment variable.
In Java you will be able to get an object with all the services with:
JSONObject vcap = new JSONObject(System.getenv("VCAP_SERVICES"));
https://docs.run.pivotal.io/devguide/deploy-apps/environment-variable.html for more information on provided environment variables.