Clojure Leiningen compile error with multiple projects - ClassNotFoundException

Question

I have a clojure library rotary, which is used by my own project api. I have a second project called pipeline, which uses api, and does not touch rotary directly.

I have tried clearing my .lein folder, and always use lein clean before compiling.

What I see:

1. Rotary compiles and installs correctly. I can use it from both repl and standalone jars.
2. Api compiles and installs correctly. Functions that use rotary work from repl and standalone jars.

If I comment out the rotary library from api, then the pipeline project, which uses api, compiles fine, and all non-rotary functionality works. This all makes sense to me.

However, when I leave rotary in api, after I lein install it, then the pipeline project errors on compile.

I am at an extreme loss on why api would work with rotary, while pipeline errors out, especially when I can narrow it down to rotary through commenting it out. If there were a problem with the rotary code, then I would expect rotary / api to fail to compile, especially as pipeline doesn't use rotary directly.

Attached is the error, taken from the pipeline project lein compile command:

Exception in thread "main" java.lang.ExceptionInInitializerError, compiling:(channel.clj:1)
at clojure.lang.Compiler$InvokeExpr.eval(Compiler.java:3387)
at clojure.lang.Compiler.compile1(Compiler.java:7035)
at clojure.lang.Compiler.compile1(Compiler.java:7025)
at clojure.lang.Compiler.compile(Compiler.java:7097)
at clojure.lang.RT.compile(RT.java:387)
at clojure.lang.RT.load(RT.java:427)
at clojure.lang.RT.load(RT.java:400)
at clojure.core$load$fn__4890.invoke(core.clj:5415)
at clojure.core$load.doInvoke(core.clj:5414)
at clojure.lang.RestFn.invoke(RestFn.java:408)
at clojure.core$load_one.invoke(core.clj:5227)
at clojure.core$load_lib.doInvoke(core.clj:5264)
at clojure.lang.RestFn.applyTo(RestFn.java:142)
at clojure.core$apply.invoke(core.clj:603)
at clojure.core$load_libs.doInvoke(core.clj:5298)
at clojure.lang.RestFn.applyTo(RestFn.java:137)
at clojure.core$apply.invoke(core.clj:603)
at clojure.core$require.doInvoke(core.clj:5381)
at clojure.lang.RestFn.invoke(RestFn.java:619)
at pipeline.core$loading__4784__auto__.invoke(core.clj:1)
at clojure.lang.AFn.applyToHelper(AFn.java:159)
at clojure.lang.AFn.applyTo(AFn.java:151)
at clojure.lang.Compiler$InvokeExpr.eval(Compiler.java:3382)
at clojure.lang.Compiler.compile1(Compiler.java:7035)
at clojure.lang.Compiler.compile1(Compiler.java:7025)
at clojure.lang.Compiler.compile(Compiler.java:7097)
at clojure.lang.RT.compile(RT.java:387)
at clojure.lang.RT.load(RT.java:427)
at clojure.lang.RT.load(RT.java:400)
at clojure.core$load$fn__4890.invoke(core.clj:5415)
at clojure.core$load.doInvoke(core.clj:5414)
at clojure.lang.RestFn.invoke(RestFn.java:408)
at clojure.core$load_one.invoke(core.clj:5227)
at clojure.core$compile$fn__4895.invoke(core.clj:5426)
at clojure.core$compile.invoke(core.clj:5425)
at user$eval7.invoke(NO_SOURCE_FILE:1)
at clojure.lang.Compiler.eval(Compiler.java:6511)
at clojure.lang.Compiler.eval(Compiler.java:6501)
at clojure.lang.Compiler.eval(Compiler.java:6477)
at clojure.core$eval.invoke(core.clj:2797)
at clojure.main$eval_opt.invoke(main.clj:297)
at clojure.main$initialize.invoke(main.clj:316)
at clojure.main$null_opt.invoke(main.clj:349)
at clojure.main$main.doInvoke(main.clj:427)
at clojure.lang.RestFn.invoke(RestFn.java:421)
at clojure.lang.Var.invoke(Var.java:419)
at clojure.lang.AFn.applyToHelper(AFn.java:163)
at clojure.lang.Var.applyTo(Var.java:532)
at clojure.main.main(main.java:37)
Caused by: java.lang.ExceptionInInitializerError
at java.lang.Class.forName0(Native Method)
at java.lang.Class.forName(Class.java:249)
at clojure.lang.RT.loadClassForName(RT.java:2056)
at clojure.lang.RT.load(RT.java:419)
at clojure.lang.RT.load(RT.java:400)
at clojure.core$load$fn__4890.invoke(core.clj:5415)
at clojure.core$load.doInvoke(core.clj:5414)
at clojure.lang.RestFn.invoke(RestFn.java:408)
at clojure.core$load_one.invoke(core.clj:5227)
at clojure.core$load_lib.doInvoke(core.clj:5264)
at clojure.lang.RestFn.applyTo(RestFn.java:142)
at clojure.core$apply.invoke(core.clj:603)
at clojure.core$load_libs.doInvoke(core.clj:5298)
at clojure.lang.RestFn.applyTo(RestFn.java:137)
at clojure.core$apply.invoke(core.clj:603)
at clojure.core$require.doInvoke(core.clj:5381)
at clojure.lang.RestFn.invoke(RestFn.java:436)
at api.db.dynamo$loading__4784__auto__.invoke(dynamo.clj:1)
at api.db.dynamo__init.load(Unknown Source)
at api.db.dynamo__init.<clinit>(Unknown Source)
at java.lang.Class.forName0(Native Method)
at java.lang.Class.forName(Class.java:249)
at clojure.lang.RT.loadClassForName(RT.java:2056)
at clojure.lang.RT.load(RT.java:419)
at clojure.lang.RT.load(RT.java:400)
at clojure.core$load$fn__4890.invoke(core.clj:5415)
at clojure.core$load.doInvoke(core.clj:5414)
at clojure.lang.RestFn.invoke(RestFn.java:408)
at clojure.core$load_one.invoke(core.clj:5227)
at clojure.core$load_lib.doInvoke(core.clj:5264)
at clojure.lang.RestFn.applyTo(RestFn.java:142)
at clojure.core$apply.invoke(core.clj:603)
at clojure.core$load_libs.doInvoke(core.clj:5298)
at clojure.lang.RestFn.applyTo(RestFn.java:137)
at clojure.core$apply.invoke(core.clj:603)
at clojure.core$require.doInvoke(core.clj:5381)
at clojure.lang.RestFn.invoke(RestFn.java:457)
at api.db.core$loading__4784__auto__.invoke(core.clj:1)
at api.db.core__init.load(Unknown Source)
at api.db.core__init.<clinit>(Unknown Source)
at java.lang.Class.forName0(Native Method)
at java.lang.Class.forName(Class.java:249)
at clojure.lang.RT.loadClassForName(RT.java:2056)
at clojure.lang.RT.load(RT.java:419)
at clojure.lang.RT.load(RT.java:400)
at clojure.core$load$fn__4890.invoke(core.clj:5415)
at clojure.core$load.doInvoke(core.clj:5414)
at clojure.lang.RestFn.invoke(RestFn.java:408)
at clojure.core$load_one.invoke(core.clj:5227)
at clojure.core$load_lib.doInvoke(core.clj:5264)
at clojure.lang.RestFn.applyTo(RestFn.java:142)
at clojure.core$apply.invoke(core.clj:603)
at clojure.core$load_libs.doInvoke(core.clj:5298)
at clojure.lang.RestFn.applyTo(RestFn.java:137)
at clojure.core$apply.invoke(core.clj:603)
at clojure.core$require.doInvoke(core.clj:5381)
at clojure.lang.RestFn.invoke(RestFn.java:436)
at api.thing$loading__4784__auto__.invoke(thing.clj:1)
at api.thing__init.load(Unknown Source)
at api.thing__init.<clinit>(Unknown Source)
at java.lang.Class.forName0(Native Method)
at java.lang.Class.forName(Class.java:249)
at clojure.lang.RT.loadClassForName(RT.java:2056)
at clojure.lang.RT.load(RT.java:419)
at clojure.lang.RT.load(RT.java:400)
at clojure.core$load$fn__4890.invoke(core.clj:5415)
at clojure.core$load.doInvoke(core.clj:5414)
at clojure.lang.RestFn.invoke(RestFn.java:408)
at clojure.core$load_one.invoke(core.clj:5227)
at clojure.core$load_lib.doInvoke(core.clj:5264)
at clojure.lang.RestFn.applyTo(RestFn.java:142)
at clojure.core$apply.invoke(core.clj:603)
at clojure.core$load_libs.doInvoke(core.clj:5298)
at clojure.lang.RestFn.applyTo(RestFn.java:137)
at clojure.core$apply.invoke(core.clj:603)
at clojure.core$require.doInvoke(core.clj:5381)
at clojure.lang.RestFn.invoke(RestFn.java:436)
at pipeline.jobs.channel$loading__4784__auto__.invoke(channel.clj:1)
at clojure.lang.AFn.applyToHelper(AFn.java:159)
at clojure.lang.AFn.applyTo(AFn.java:151)
at clojure.lang.Compiler$InvokeExpr.eval(Compiler.java:3382)
... 48 more

Caused by: java.lang.ClassNotFoundException: com.amazonaws.services.dynamodbv2.model.BatchGetItemResult
at java.net.URLClassLoader$1.run(URLClassLoader.java:202)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:190)
at java.lang.ClassLoader.loadClass(ClassLoader.java:306)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301)
at java.lang.ClassLoader.loadClass(ClassLoader.java:247)
at java.lang.Class.forName0(Native Method)
at java.lang.Class.forName(Class.java:171)
at rotary.client__init.__init0(Unknown Source)
at rotary.client__init.<clinit>(Unknown Source)
... 129 more

Answer 1

This happens for me when I attempt to load multiple versions of a dependency because two of my dependencies depend in turn on the same library with different versions. You can check for this by running:

lein deps :tree

then look for the duplicated dependency and ad an exclude statement to one of the dependencies so there is only one dependency attempting to fill the requirement.

[org.jclouds.driver/jclouds-slf4j "1.5.5"                  
  :exclusions [org.slf4j/slf4j-api]]

I have also seen this with projects that expect you to provide a library that fills a particular interface and I use the wrong version. For instance using pallet with the wrong version of jClouds, though this is much less common than overlapping dependencies.
If it's none of these then it is very likely that someone in the #clojure irc channel on freenode.net will be able to walk you through debugging it.