How to fix a "Java failed to load class" when using custom Java class using JLink?

Question

I have a Java project compiled into a jar file with a class called HttpClientSSO.

The commandline

java -cp bota.jar org.nilostep.bota.HttpClientSSO

executes the class successfully.

I want to run the class from a Mathematica Notebook. I did the following:

Needs["JLink`"]
ReinstallJava[];
LoadJavaClass["java.lang.System"];
java`lang`System`getProperty["java.version"]
DIR = "D:\\Dropbox\\DATA\\MyJavaProjects\\bota\\out\\artifacts\\bota_jar\\bota.jar";
AddToClassPath[DIR];
frm = JavaNew["java.awt.Frame"]
conn = JavaNew["org.nilostep.bota.HttpClientSSO"]

Execution returns:

1.7.0_13

JavaObject[java.awt.Frame]

$Failed

In the Mathematica message frame I get the following error:

Java failed to load class org.nilostep.bota.HttpClientSSO. >>

I have also tried:

 ReinstallJava[ClassPath -> "D:\\Dropbox\\DATA\\MyJavaProjects\\bota\\out\\artifacts\\bota_jar\\bota.jar"]
 LoadJavaClass["org.nilostep.bota.HttpClientSSO"];
 conn = JavaNew["org.nilostep.bota.HttpClientSSO"]

but also with the result $Failed

How do I fix this?

Answer 1

The problem was the following, the custom .jar was created with Java 8, Mma 10.3 comes with Java 7, the real error was a version issue.

Needs["JLink`"]
DIR = "D:\\Dropbox\\DATA\\MyJavaProjects\\bota\\out\\artifacts\\bota_jar\\bota.jar";
ReinstallJava[CommandLine -> "C:\\Progra~1\\Java\\jdk1.8.0_45\\jre\\bin\\java", ClassPath -> DIR];
LoadJavaClass["java.lang.System"];
java`lang`System`getProperty["java.version"]
frm = JavaNew["java.awt.Frame"]
(*AddToClassPath[DIR];*)
conn = JavaNew["org.nilostep.bota.HttpClientSSO"]

worked as expected.