方法

AWSCLIで取得してjqで取り出す

SecretsManager(/secret/rds/app)
{
  "spring.datasource.username": "app",
  "spring.datasource.password": "P@ssw0rd!!"
}
cmd
aws secretsmanager get-secret-value --secret-id /secret/rds/app | jq -r ".SecretString | fromjson | .[\"spring.datasource.password\"]"
powershell
aws secretsmanager get-secret-value --secret-id /secret/rds/app | jq -r ".SecretString | fromjson | .[\""spring.datasource.password\""]"

参考