From 60c1e6660f5d767dbc2904b7f54a530e9b5993cc Mon Sep 17 00:00:00 2001
From: Sean Corfield <sean@corfield.org>
Date: Wed, 17 Jul 2019 23:50:56 -0700
Subject: [PATCH] Support connection pooling more easily

---
 CHANGELOG.md                       |  2 +-
 deps.edn                           |  7 ++++++-
 src/next/jdbc/connection.clj       | 10 +++++++++-
 src/next/jdbc/specs.clj            |  6 ++++++
 test/next/jdbc/connection_test.clj | 11 ++++++++++-
 5 files changed, 32 insertions(+), 4 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 5c412a3..fc4e1ed 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -6,7 +6,7 @@ Only accretive/fixative changes will be made from now on.
 
 The following changes have been committed to the **master** branch since the 1.0.2 release:
 
-* None.
+* Address #48 by adding `next.jdbc.connection/jdbc-url` and showing HikariCP and c3p0 connection pooling (so far it's just tests).
 
 ## Stable Builds
 
diff --git a/deps.edn b/deps.edn
index 9ff2128..ed6dff4 100644
--- a/deps.edn
+++ b/deps.edn
@@ -1,8 +1,13 @@
 {:paths ["src"]
- :deps {org.clojure/clojure {:mvn/version "1.10.1"}}
+ :deps {org.clojure/clojure {:mvn/version "1.10.1"}
+        org.clojure/java.data {:mvn/version "0.1.1"}}
  :aliases
  {:test {:extra-paths ["test"]
          :extra-deps {org.clojure/test.check {:mvn/version "0.9.0"}
+                      ;; connection pooling
+                      com.zaxxer/HikariCP {:mvn/version "3.3.1"}
+                      com.mchange/c3p0 {:mvn/version "0.9.5.4"}
+                      ;; JDBC drivers
                       org.apache.derby/derby {:mvn/version "10.14.2.0"}
                       org.hsqldb/hsqldb {:mvn/version "2.4.1"}
                       com.h2database/h2 {:mvn/version "1.4.197"}
diff --git a/src/next/jdbc/connection.clj b/src/next/jdbc/connection.clj
index 4ceabb9..23107f0 100644
--- a/src/next/jdbc/connection.clj
+++ b/src/next/jdbc/connection.clj
@@ -2,7 +2,8 @@
 
 (ns next.jdbc.connection
   "Standard implementations of `get-datasource` and `get-connection`."
-  (:require [next.jdbc.protocols :as p])
+  (:require [clojure.java.data :refer [to-java]]
+            [next.jdbc.protocols :as p])
   (:import (java.sql Connection DriverManager)
            (javax.sql DataSource)
            (java.util Properties)))
@@ -191,6 +192,13 @@
       (throw (ex-info (str "Unknown dbtype: " dbtype) db-spec)))
     [url etc]))
 
+(defn jdbc-url
+  "Given a connection pooling class and a database spec, return an connection
+  pool object built from the database spec."
+  [clazz db-spec]
+  (let [[url etc] (spec->url+etc db-spec)]
+    (to-java clazz (assoc etc :jdbcUrl url))))
+
 (defn- string->url+etc
   "Given a JDBC URL, return it with an empty set of options with no parsing."
   [s]
diff --git a/src/next/jdbc/specs.clj b/src/next/jdbc/specs.clj
index dc7f24d..a5dbd67 100644
--- a/src/next/jdbc/specs.clj
+++ b/src/next/jdbc/specs.clj
@@ -17,6 +17,7 @@
   (:require [clojure.spec.alpha :as s]
             [clojure.spec.test.alpha :as st]
             [next.jdbc :as jdbc]
+            [next.jdbc.connection :as connection]
             [next.jdbc.prepare :as prepare]
             [next.jdbc.sql :as sql])
   (:import (java.sql Connection PreparedStatement)
@@ -113,6 +114,10 @@
                                             :opts (s/? ::opts-map)))
                      :body (s/* any?)))
 
+(s/fdef connection/jdbc-url
+        :args (s/cat :clazz #(instance? Class %)
+                     :db-spec ::db-spec-map))
+
 (s/fdef prepare/execute-batch!
         :args (s/cat :ps ::prepared-statement
                      :param-groups (s/coll-of ::params :kind sequential?)
@@ -187,6 +192,7 @@
                   `jdbc/execute-one!
                   `jdbc/transact
                   `jdbc/with-transaction
+                  `connection/jdbc-url
                   `prepare/execute-batch!
                   `prepare/set-parameters
                   `sql/insert!
diff --git a/test/next/jdbc/connection_test.clj b/test/next/jdbc/connection_test.clj
index c9bfe2b..d10a08c 100644
--- a/test/next/jdbc/connection_test.clj
+++ b/test/next/jdbc/connection_test.clj
@@ -6,7 +6,8 @@
 
   At some point, the datasource/connection tests should probably be extended
   to accept EDN specs from an external source (environment variables?)."
-  (:require [clojure.string :as str]
+  (:require [clojure.java.data :refer [to-java]]
+            [clojure.string :as str]
             [clojure.test :refer [deftest is testing]]
             [next.jdbc.connection :as c]
             [next.jdbc.protocols :as p]))
@@ -103,4 +104,12 @@
           (is (instance? java.sql.Connection con)))))
     (testing "connection via map (Object)"
       (with-open [con (p/get-connection db {})]
+        (is (instance? java.sql.Connection con))))
+    (testing "connection via HikariCP"
+      (with-open [con (p/get-connection (c/jdbc-url com.zaxxer.hikari.HikariDataSource db)
+                                        {})]
+        (is (instance? java.sql.Connection con))))
+    (testing "connection via c3p0"
+      (with-open [con (p/get-connection (c/jdbc-url com.mchange.v2.c3p0.ComboPooledDataSource db)
+                                        {})]
         (is (instance? java.sql.Connection con))))))