Overriding server connector config with env variables with dropwizard

Question

I have posted this question on dw mailing list but didnt get an answer.

Can I assume the YML format below doesnt work for DW 0.7.0 anymore? (The use of @ char to ins

Answer 1

Starting from Dropwizard version 0.8.0, you can access environment variables from the configuration yml file. It also supports setting a default value in case the environment variable is not available. See the docs here.

Example

// put environment variable inside ${}
// use :- operator to provide default value

dbHost: ${DB_HOST}
dbPort: ${DB_PORT:-1234}
// dbPort = 1234, if DB_PORT environment variable has no value

Important Note: For this to work you need to set up a SubstitutingSourceProvider with an EnvironmentVariableSubstitutor.

// Enable variable substitution with environment variables
bootstrap.setConfigurationSourceProvider(
    new SubstitutingSourceProvider(
        bootstrap.getConfigurationSourceProvider(),
        new EnvironmentVariableSubstitutor())
);

Update: 15/Nov/2017 As mentioned by @EFreak in the comments section, new EnvironmentVariableSubstitutor() will throw UndefinedEnvironmentVariableException if the environment variable is not defined, unless you set strict mode to false by using new EnvironmentVariableSubstitutor(false) https://github.com/dropwizard/dropwizard/blob/master/dropwizard-configuration/src/main/java/io/dropwizard/configuration/EnvironmentVariableSubstitutor.java