Receiving "missing class name" errors when running Logstash with Azure blob input

When I run logstash with the Azure blob input configured, I get the following error:

2018-10-10T11:42:18,296][ERROR][logstash.inputs.logstashinputazureblob] Oh My, An error occurred. Error:missing class name (`javax.json.Json'): Trace: ["org/jruby/javasupport/JavaPackage.java:127:in `const_missing'", "C:/ELK/Logstash/vendor/bundle/jruby/2.3.0/gems/logstash-input-azureblob-0.9.13-java/lib/com/microsoft/json-parser.rb:22:in `initialize'", "C:/ELK/Logstash/vendor/bundle/jruby/2.3.0/gems/logstash-input-azureblob-0.9.13-java/lib/logstash/inputs/azureblob.rb:192:in `process'", "C:/ELK/Logstash/vendor/bundle/jruby/2.3.0/gems/logstash-input-azureblob-0.9.13-java/lib/logstash/inputs/azureblob.rb:151:in `run'", "C:/ELK/Logstash/logstash-core/lib/logstash/pipeline.rb:512:in `inputworker'", "C:/ELK/Logstash/logstash-core/lib/logstash/pipeline.rb:505:in `block in start_input'"] {:exception=>#}

Some more info in case it helps... I only got to this point after:

- Commenting out line 3 of the "json-parser.rb" file to resolve the error reported in #170
- Running logstash on a 64 bit Java installation as I was getting out of memory errors when running in 32 bit mode (even with the heap size adjusted as high as it could go)

What I'm trying to do is ingest NSG flow logs, similar to what is described [here](https://docs.microsoft.com/en-us/azure/network-watcher/network-watcher-visualize-nsg-flow-logs-open-source-tools).

My config:

input {
azureblob
{
storage_account_name => "xxxxxxxxx"
storage_access_key => "xxxxxxxxx"
container => "xxxxxxxxxxx"
codec => "json"
}
}

filter {
split { field => "[records]" }
split { field => "[records][properties][flows]"}
split { field => "[records][properties][flows][flows]"}
split { field => "[records][properties][flows][flows][flowTuples]"}


mutate {
split => { "[records][resourceId]" => "/"}
add_field => {"Subscription" => "%{[records][resourceId][2]}"
"ResourceGroup" => "%{[records][resourceId][4]}"
"NetworkSecurityGroup" => "%{[records][resourceId][8]}"}
convert => {"Subscription" => "string"}
convert => {"ResourceGroup" => "string"}
convert => {"NetworkSecurityGroup" => "string"}
split => { "[records][properties][flows][flows][flowTuples]" => ","}
add_field => {
"unixtimestamp" => "%{[records][properties][flows][flows][flowTuples][0]}"
"srcIp" => "%{[records][properties][flows][flows][flowTuples][1]}"
"destIp" => "%{[records][properties][flows][flows][flowTuples][2]}"
"srcPort" => "%{[records][properties][flows][flows][flowTuples][3]}"
"destPort" => "%{[records][properties][flows][flows][flowTuples][4]}"
"protocol" => "%{[records][properties][flows][flows][flowTuples][5]}"
"trafficflow" => "%{[records][properties][flows][flows][flowTuples][6]}"
"traffic" => "%{[records][properties][flows][flows][flowTuples][7]}"
}
convert => {"unixtimestamp" => "integer"}
convert => {"srcPort" => "integer"}
convert => {"destPort" => "integer"}
}


date{
match => ["unixtimestamp" , "UNIX"]
}
}


output {
file {
path => "c:\elk\output\nsglogs.txt"
}
}