[jdbc] Try to unwrap any java.sql.Connection instance for dispatch purposes (#206)

Author: alexander-yakushev

src/toucan2/jdbc.clj

@@ -24,15 +24,12 @@
                            "com.mysql.cj.MysqlConnection"])
   (require 'toucan2.jdbc.mysql-mariadb))
 
-;;; c3p0 and Hikari integration: when we encounter a wrapped connection pool connection, dispatch off of the class of
-;;; connection it wraps
-(doseq [pool-connection-class-name ["com.mchange.v2.c3p0.impl.NewProxyConnection"
-                                    "com.zaxxer.hikari.pool.HikariProxyConnection"]]
-  (when-let [pool-connection-class (class-for-name pool-connection-class-name)]
-    (extend pool-connection-class
-      protocols/IDispatchValue
-      {:dispatch-value (fn [^java.sql.Wrapper conn]
-                         (try
-                           (protocols/dispatch-value (.unwrap conn java.sql.Connection))
-                           (catch Throwable _
-                             pool-connection-class)))})))
+;;; c3p0 and Hikari integration, or any other library that wraps real SQL connections: when we encounter a wrapped
+;;; connection, dispatch off of the class of connection it wraps
+(extend java.sql.Connection
+  protocols/IDispatchValue
+  {:dispatch-value (fn [^java.sql.Wrapper conn]
+                     (try
+                       (type (.unwrap conn java.sql.Connection))
+                       (catch Throwable _
+                         (type conn))))})

src/toucan2/tools/identity_query.clj

@@ -74,6 +74,14 @@
 ;;;; Identity connection
 
 (deftype ^:no-doc IdentityConnection []
+  java.sql.Wrapper
+  (isWrapperFor [_this klass]
+    (= klass java.sql.Connection))
+  (unwrap [this klass]
+    (if (.isWrapperFor this klass)
+      this
+      (throw (ex-info (str "IdentityConnection is not the wrapper for " klass) {}))))
+
   pretty/PrettyPrintable
   (pretty [_this]
     (list `->IdentityConnection)))

test/toucan2/tools/identity_query_test.clj

@@ -10,6 +10,8 @@
    [toucan2.tools.identity-query :as identity-query]
    [toucan2.tools.named-query :as tools.named-query]))
 
+(set! *warn-on-reflection* true)
+
 (deftest ^:parallel query-test
   (is (= [[1 2]
           [:a :b]]
@@ -81,6 +83,10 @@
       (testing "Return plain rows, not instances"
         (is (not (instance/instance? (first results))))))))
 
+(deftest ^:parallel can-unwrap-identity-connection
+  (let [conn (identity-query/->IdentityConnection)]
+    (is (identical? conn (.unwrap ^java.sql.Wrapper conn java.sql.Connection)))))
+
 ;; (deftest ^:parallel insert-test
 ;;   (testing "Can we use identity-query with insert?"
 ;;     (is (= [(instance/instance :venues {:a 1})]