The Java example you shared is different than the JSON one (BTW please indent your code to make it readable).
In Java, you are writing a document like:
{
"application_id":"6"
}
In Java, you are writing a document like:
{
"application_id":"6"
}
The Json version is:
{
"entity": {
"application_id": 6
}
}
Not the same field name application_id vs entity.application_id, not the same format number vs string... So probably not the same mapping.
About you Java code unless you have only one primary shard, the code is not going to work and probably to compile.
You are calling index method with a GetRequest. I doubt this can work.