berezovskyi / dns-test

Test whether a domain has a configured DNS server

Simple Java snippet test turned into madness

I was working on another project and wanted to see how easy it is to check if the domain exists (i.e. it's not just the server that is down now), but w/o doing all those WHOIS request to all the different registries.

I found http://www.xbill.org/dnsjava/dnsjava-current/examples.html and wanted to try it out. Let's run this Java snippet quickly. After all, Java development is my daily job. Right?

Wrong! To write a (proper) minimal Java program that takes a single command-line argument, I had to do the following:

1. Use maven-archetype-quickstart. Sets up the pom.xml properly and creates a class with a main method. I do not mention a ton of fields that need to be filled.
2. Add maven dependency for the library I want to play with. The most pleasant step of the this process.
3. Adjust the snippet to my needs. Nothing special here.
4. Try automating the execution of the main method with exec-maven-plugin. Partial success from the second try, but program output is surrounded with maven log statements.
5. Try using maven-jar-plugin for the same purpose. Fail because the jar does not have the necessary classes on the classpath.
6. maven-shade-plugin was used to make a proper jar file that can be executed. Still, you need the java idiosyncrasy java -jar target/xxx.jar. Worse, you can't put that into README because it will break when the version changes.
7. Finally, we add the appassembler-maven-plugin plugin to the mix to produce binary wrappers.

P.S. I also had to look up a .gitignore file for Java, Maven, and Intellij.

Usage

$ mvn clean package appassembler:assemble
$ sh target/appassembler/bin/dns-test google.com
Host google.com has nameserver ns2.google.com.
Host google.com has nameserver ns1.google.com.
Host google.com has nameserver ns4.google.com.
Host google.com has nameserver ns3.google.com.
$ sh target/appassembler/bin/dns-test dwvwdv3r.ed
Host dwvwdv3r.ed has no nameservers

Or

mvn clean compile exec:java -Dexec.args="facebook.com"
[INFO] Scanning for projects...
[INFO]
[INFO] ------------------------------------------------------------------------
[INFO] Building dns-test 0.0.1-SNAPSHOT
[INFO] ------------------------------------------------------------------------
[INFO]
[INFO] --- maven-clean-plugin:2.5:clean (default-clean) @ dns-test ---
[INFO] Deleting /Users/andrew/code/dns-test/target
[INFO]
[INFO] --- maven-resources-plugin:2.6:resources (default-resources) @ dns-test ---
[INFO] Using 'UTF-8' encoding to copy filtered resources.
[INFO] skip non existing resourceDirectory /Users/andrew/code/dns-test/src/main/resources
[INFO]
[INFO] --- maven-compiler-plugin:3.1:compile (default-compile) @ dns-test ---
[INFO] Changes detected - recompiling the module!
[INFO] Compiling 1 source file to /Users/andrew/code/dns-test/target/classes
[INFO]
[INFO] --- exec-maven-plugin:1.5.0:java (default-cli) @ dns-test ---
Host facebook.com has nameserver a.ns.facebook.com.
Host facebook.com has nameserver b.ns.facebook.com.
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 1.952 s
[INFO] Finished at: 2016-11-06T02:05:35+01:00
[INFO] Final Memory: 15M/212M
[INFO] ------------------------------------------------------------------------

With a bit of magic, we can do even better:

$ mvn -q clean compile exec:java -Dexec.args="facebook.com"
Host facebook.com has nameserver b.ns.facebook.com.
Host facebook.com has nameserver a.ns.facebook.com.