How to convert ArrayList to JSON in Java

I have an ArrayList, which has a bunch of domain objects As follows:

Domain [domainId=19,name=a,dnsName=a.com,type=0,flags=0]
Domain [domainId=20,name=b,dnsName=b.com,flags=12]
Domain [domainId=21,name=c,dnsName=c.com,flags=0]
Domain [domainId=22,name=d,dnsName=d.com,flags=0]

My question is how to convert ArrayList to JSON? The data format shall be:

{  
"param":{  
  "domain":[  
    {  
      "domid":19,"name":"a","dnsname":"a.com","type":0,"flags":
    },...
  ]
}

Solution

I'm not sure if it's exactly what you need, but you can use the gson Library (link) to convert ArrayList to JSON

ArrayList<String> list = new ArrayList<String>();
list.add("str1");
list.add("str2");
list.add("str3");
String json = new Gson().toJson(list);

Or in your case:

ArrayList<Domain> list = new ArrayList<Domain>();
list.add(new Domain());
list.add(new Domain());
list.add(new Domain());
String json = new Gson().toJson(list);

If for some reason you find it more convenient, you can also traverse the ArrayList and build JSON from each domain object in the list

String toJSON(ArrayList<Domain> list) {
    Gson gson = new Gson();
    StringBuilder sb = new StringBuilder();
    for(Domain d : list) {
        sb.append(gson.toJson(d));
    }
    return sb.toString();
}