Introduce monger.core/connect! and monger.core/set-db!

Even though it is not idiomatic Clojure to mutate vars like this,
it is very common for many applications to only use one MongoDB
connection (so, no per-thread var rebinding) and one main database.

For those cases, these function eliminate the need for mundaine
hacks with namespace switching.

src/monger/core.clj

@@ -11,7 +11,7 @@
       :doc "Thin idiomatic wrapper around MongoDB Java client. monger.core includes
        fundamental functions that work with connections & databases. Most of functionality
        is in the monger.collection namespace."}
-    monger.core
+  monger.core
   (:refer-clojure :exclude [count])
   (:use [monger.conversion])
   (:import (com.mongodb Mongo DB WriteConcern DBObject DBCursor)
@@ -48,6 +48,7 @@
   ([{ :keys [host port] :or { host *mongodb-host*, port *mongodb-port* }}]
      (Mongo. ^String host ^Long port)))
 
+
 (defn ^DB get-db
   "Get database reference by name.
 
@@ -61,6 +62,16 @@
      (.getDB connection name)))
 
 
+(defn connect!
+  ^Mongo [& args]
+  (def ^:dynamic *mongodb-connection* (apply connect args)))
+
+
+(defn set-db!
+  [db]
+  (def ^:dynamic *mongodb-database* db))
+
+
 
 (defprotocol Countable
   (count [this] "Returns size of the object"))

test/monger/test/core.clj

@@ -4,9 +4,8 @@
   (:use [clojure.test]))
 
 
-(monger.util/with-ns 'monger.core
-  (defonce ^:dynamic *mongodb-connection* (monger.core/connect))
-  (defonce ^:dynamic *mongodb-database*   (monger.core/get-db "monger-test")))
+(monger.core/connect!)
+(monger.core/set-db! (monger.core/get-db "monger-test"))
 
 
 (deftest connect-to-mongo-with-default-host-and-port