class someclass {
    attr1
    attr2
    attr3
    ....
}

{"namespace": "your.package.name",
 "type": "record",
 "name": "SomeClass",
 "fields": [
     {"name": "attr1", "type": "YourType1"},
     {"name": "attr2", "type": "YourType2"},
     {"name": "attr3", "type": "YourType3"}
 ]
}