Define a Database Connection

View the Database_URL configuration variable for the Heroku Database and define a name to represent that in Clojure

Use the Heroku Toolbelt to view the configuration variables

heroku config

Edit the file src/todo_list/core.clj file and add the following definition towards the top of the file. Substitute your own database connection values for :subname, user and password.

(def postgres {:subprotocol "postgresql"
               :subname "//ec2-54-225-134-223.compute-1.amazonaws.com:5432/d9mtan2ol8uhik"
               :user "trhrcgefmyolkw"
               :password "hiFKxwqt9xT7MJ97hjri_c98Nm"
               :ssl true
               :sslmode true
               :sslfactory "org.postgresql.ssl.NonValidatingFactory"})

Breaking down the Heroku Postgres connection string into a map allows us to easily add options to the connection string whilst keeping it readable.

Also, a JDBC connection string has a slightly different form to the Heroku string. Heroku Posgres creates a configuration variable in the form of postgres://[user]:[password]@[host]:[port]/[database] whereas the JDBC connection string is of the form `jdbc:postgres://[host]:[port]/[database]?user=[user]&password=[pass]

JdBC connection string for Heroku Postgres

jdbc:postgresql://[host]:[port]/[database]?user=[user]&password=[password]&ssl=true&sslfactory=org.postgresql.ssl.NonValidatingFactory.

Converting the map back to a JDBC connection string

(defn remote-heroku-db-spec [host port database username password]
  {:connection-uri (str "jdbc:postgresql://" host ":" port "/" database "?user=" username "&password=" password "&ssl=true&sslfactory=org.postgresql.ssl.NonValidatingFactory")})

From Heroku

The DATABASE_URL for the Heroku Postgres add-on follows this naming convention:

postgres://:<password>@/

However the Postgres JDBC driver uses the following convention:

jdbc:postgresql://:/?user=&password=

Notice the additional ql at the end of jdbc:postgresql. Due to this difference you will need to hardcode the scheme to jdbc:postgresql

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