Creating an uberjar for a project that uses MySQL and SQLServer
clojure, jar, java, jdbc, leiningen
Solution
The problem is most likely that when making the uber-jar, you are not copying some files (eg `.properties` or XML config) that are required by the driver, or you are overwriting files that exist in both JDBC drivers.
A good example of overwriting is the `META-INF/services/java.sql.Driver` file which all JDBC 4 drivers have. This file contains a list of all classes in the jar implementing `java.sql.Driver`, so that the `java.sqlDriverManager` class can automatically load all Driver implementations using `ServiceLoader`.
If you create an uber-jar with multiple JDBC drivers, you either need to make sure this file contains the union of all these files, or your application needs to explicitly load the drivers you need with `Class.forName("<name of the java.sql.Driver implementation>")` for each required driver and not depend on the JDBC 4 driver autoloading.
Also verify that the process you use to create the uber-jar copies all resources and not just `.class` files!
Better yet (in my opinion), don't use an uber-jar, but keep the dependent `.jar` files external and reference them in the `Class-Path` entry of the `META-INF/MANIFEST.MF` file of your application, this saves you a lot of hassle to get your uber-jar working correctly (or verify that it is actually working correctly).
Problem
I'm trying to build a project in clojure that takes data from a Microsoft SQL Server database, and pushes it to a MySQL database. The project runs fine using lein run, but when I package it into an uberjar using leiningen, and run it using java -jar, it fails with: Exception in thread "main" java.sql.SQLException: No suitable driver found for jdbc:sqlserver.... This error only happens when I attempt to use both the MySQL database and the SQL Server database. If I use any one of them on its own, the jar file runs fine using java -jar. My project.clj is as follows: ``` (defproject sqlserver-clojure "1.0.0-SNAPSHOT" :description "A minimal example of the MySQL/SQLServer conflict" :dependencies [[org.clojure/clojure "1.4.0"] [com.microsoft/sqljdbc4 "3.0"] [clojureql "1.0.4"] [mysql/mysql-connector-java "5.1.6"]] :main sqlserverclojure.core) ```