How to create schema containing list of objects using Avro?

Question

Does anyone knows how to create Avro schema which contains list of objects of some class?

I want my generated classes to look like below :

class Child {     String name; }  class Parent {     list<Child> children; } 

For this, I have written part of schema file but do not know how to tell Avro to create list of objects of type Children?

My schema file looks like below :

{     "name": "Parent",     "type":"record",     "fields":[         {             "name":"children",             "type":{                 "name":"Child",                 "type":"record",                 "fields":[                     {"name":"name", "type":"string"}                 ]             }         }     ]  } 

Now problem is that I can mark field children as either Child type or array but do not know how to mark it as a array of objects of type Child class?

Can anyone please help?

Answer 1

You need to use array type for creating the list. Following is the updated schema that handles your usecase.

{     "name": "Parent",     "type":"record",     "fields":[         {             "name":"children",             "type":{                 "type": "array",                   "items":{                     "name":"Child",                     "type":"record",                     "fields":[                         {"name":"name", "type":"string"}                     ]                 }             }         }     ]  } 

Answer 2

I had following class and avro maven plugin generated two classes accordingly :

public class Employees{     String accountNumber;     String address;     List<Account> accountList;     }  public class Account {     String accountNumber;     String id; } 

Avro file format :

{     "type": "record",     "namespace": "com.mypackage",     "name": "AccountEvent",     "fields": [         {             "name": "accountNumber",             "type": "string"         },         {             "name": "address",             "type": "string"         },         {             "name": "accountList",             "type": {                 "type": "array",                 "items":{                     "name": "Account",                     "type": "record",                     "fields":[                         {   "name": "accountNumber",                             "type": "string"                         },                         {   "name": "id",                             "type": "string"                         }                     ]                 }             }         }     ] }