Fight Java with Java

Make our own version of DBRef that is exactly like the original but has one extra constructor and
implements clojure.lang.IDeref so it is possible to @dereference such refs.

This is only one small step in a proper, Clojuric, easy to use DBRef support. We may tack more Monger-specific
extensions to our DBRef implementation later.

As sang by Jetallica:

Do unto others as they have done unto you
but what in the hell is this world coming to?

Blow the universe into nothingness
nuclear warfare shall lay us to rest

Fight Java with Java
ending is near
fight Java with Java
bursting with fear

.travis.yml

@@ -2,7 +2,7 @@ language: clojure
 lein: lein2
 before_script:
   - ./bin/ci/before_script.sh
-script: lein2 ci test
+script: lein2 javac && lein2 all test
 jdk:
   - openjdk6
   - openjdk7

project.clj

@@ -21,6 +21,7 @@
                    :all           (constantly true)}
   :source-paths      ["src/clojure"]
   :java-source-paths ["src/java"]
+  :javac-options     ["-target" "1.6" "-source" "1.6"]  
   :codox {:exclude [monger.internal.pagination]}
   :mailing-list {:name "clojure-monger"
                  :archive "https://groups.google.com/group/clojure-mongodb"

src/clojure/monger/conversion.clj

@@ -69,6 +69,10 @@
   DBObject
   (to-db-object [^DBObject input] input)
 
+  com.novemberain.monger.DBRef
+  (to-db-object [^com.novemberain.monger.DBRef dbref]
+    dbref)
+
   Object
   (to-db-object [input]
     input))
@@ -99,6 +103,10 @@
   (from-db-object [^BasicDBList input keywordize]
     (vec (map #(from-db-object % keywordize) input)))
 
+  com.mongodb.DBRef
+  (from-db-object [^com.novemberain.monger.DBRef input keywordize]
+    (com.novemberain.monger.DBRef. input))
+
   DBObject
   (from-db-object [^DBObject input keywordize]
     ;; DBObject provides .toMap, but the implementation in

src/java/com/novemberain/monger/DBRef.java

@@ -0,0 +1,44 @@
+package com.novemberain.monger;
+
+import clojure.lang.IDeref;
+import com.mongodb.DB;
+import com.mongodb.DBObject;
+import org.bson.BSONObject;
+
+/**
+ * Exactly as com.mongodb.DBRef but also implements Clojure IDefer for @dereferencing
+ */
+public class DBRef extends com.mongodb.DBRef implements IDeref {
+
+  /**
+   * Creates a DBRef
+   * @param db the database
+   * @param o a BSON object representing the reference
+   */
+  public DBRef(DB db, BSONObject o) {
+    super(db , o.get("$ref").toString(), o.get("$id"));
+  }
+
+  /**
+   * Creates a DBRef
+   * @param db the database
+   * @param ns the namespace where the object is stored
+   * @param id the object id
+   */
+  public DBRef(DB db, String ns, Object id) {
+    super(db, ns, id);
+  }
+
+  /**
+   * Creates a DBRef from a com.mongodb.DBRef instance.
+   * @param source The original reference MongoDB Java driver uses
+   */
+  public DBRef(com.mongodb.DBRef source) {
+    this(source.getDB(), source.getRef(), source.getId());
+  }
+
+  @Override
+  public DBObject deref() {
+    return this.fetch();
+  }
+}

test/monger/test/inserting_test.clj

@@ -95,8 +95,10 @@
         joe   (mc/insert "owners" {:name "Joe" :_id oid})
         dbref (DBRef. (mg/current-db) coll2 oid)]
     (mc/insert coll1 {:type "pentagon" :owner dbref})
-    (let [fetched (mc/find-one-as-map coll1 {:type "pentagon"})]
-      (is (= dbref (:owner fetched))))))
+    (let [fetched (mc/find-one-as-map coll1 {:type "pentagon"})
+          fo      (:owner fetched)]
+      (is (= {:_id oid :name "Joe"} (from-db-object @fo true)))
+      (is (= dbref fo)))))
 
 
 ;;