JDK 9+ compatibility: DataHandler missing

[n2o]

In JDK9+, DataHandler appears to be dropped. Therefore, an error is thrown:

#error {
 :cause javax.activation.DataHandler
 :via
 [{:type clojure.lang.Compiler$CompilerException
   :message Syntax error compiling at (postal/message.clj:1:1).
   :data #:clojure.error{:phase :compile-syntax-check, :line 1, :column 1, :source postal/message.clj}
   :at [clojure.lang.Compiler load Compiler.java 7648]}
  {:type java.lang.ClassNotFoundException
   :message javax.activation.DataHandler
   :at [java.net.URLClassLoader findClass URLClassLoader.java 436]}]}

To add a workaround, one can add this dependency to your project:

[com.sun.activation/javax.activation "1.2.0"]

Tested with AdoptOpenJDK 13

But this is just a workaround. Please update the corresponding lines in the code base.

Thanks!

[dancek]

Adding a dependency seems to also be the correct fix per JEP 320, though [javax.activation/javax.activation-api "1.2.0"] is suggested.

The JavaMail API still uses javax.activation.DataHandler legitimately.

[caleb]

So I shouldn't have issues with postal an JDK > 8 if I add that dependency?

Would a solution for postal be to include that library or to include a mention in the README?

[dancek]

We've been using the dependency and postal in production since May, and have had no issues.

I'm not sure if adding the dependency in postal itself causes issues in JDK 8 but it's what I would do.

[wildwestrom]

Even after adding [com.sun.activation/javax.activation "1.2.0"] as a dependency, when I call send-message I get this:

2. Unhandled clojure.lang.Compiler$CompilerException
   Error compiling postal/message.clj at (1:1)
   #:clojure.error{:phase :compile-syntax-check,
                   :line 1,
                   :column 1,
                   :source "postal/message.clj"}

1. Caused by java.lang.ClassNotFoundException
   javax.mail.Message
   [stacktrace....]

java --version
openjdk 16.0.2 2021-07-20
OpenJDK Runtime Environment Homebrew (build 16.0.2+0)
OpenJDK 64-Bit Server VM Homebrew (build 16.0.2+0, mixed mode, sharing)