Create list of java objects from json

Question

I have following json which i need to convert into list of java objects.

{
  "model":[

    {
        "syscall_1":"execve",
        "syscall_2":"brk"
    },
    {
        "syscall_1":"brk",
        "syscall_2":"access"
    },
    {
        "syscall_1":"access",
        "syscall_2":"mmap"
    },
    {
        "syscall_1":"mmap",
        "syscall_2":"access"
    }
]
}

I am using gson and its TypeToken>(){}.getType() API ,however I am bit confused about how my objects should look corresponding to input json.

How can I use TypeToken in this scenario?

Jimmy · Accepted Answer · 2015-03-06 05:42:47Z

Another option (not using the type token, but still achieves what you want) would be to parse the entire json object, then access the model array like so:

import com.google.gson.Gson;

import java.util.List;


public class TestMe {

    public static void main(String[] args) {

        String jsonSt2 = "{\"model\":[{\"syscall_1\":\"execve\",\"syscall_2\":\"brk\"},{\"syscall_1\":\"brk\",\"syscall_2\":\"access\"},{\"syscall_1\":\"access\",\"syscall_2\":\"mmap\"},{\"syscall_1\":\"mmap\",\"syscall_2\":\"access\"}]}";
        System.out.println("your json: " + jsonSt2);

        ModelObject object = new Gson().fromJson(jsonSt2, ModelObject.class);

        System.out.println("Created Model object, array size is " + object.model.size());

        for (ModelItem mi : object.model) {
            System.out.println(mi.syscall_1 + " " + mi.syscall_2);
        }
    }
}

class ModelObject {
    List<ModelItem> model;
}

class ModelItem {
    String syscall_1;
    String syscall_2;
}

Output

Created Model object, array size is 4
execve brk
brk access
access mmap
mmap access
mmap access

Pasupathi Rajamanickam · Accepted Answer · 2015-03-06 05:28:35Z

If you can use org.json to parse and construct list objects, you can try this.

String jsonSt2 = "{\"model\":[{\"syscall_1\":\"execve\",\"syscall_2\":\"brk\"},{\"syscall_1\":\"brk\",\"syscall_2\":\"access\"},{\"syscall_1\":\"access\",\"syscall_2\":\"mmap\"},{\"syscall_1\":\"mmap\",\"syscall_2\":\"access\"}]}";
List<Model> models = new ArrayList<>();
JSONObject jsonModelObject = new org.json.JSONObject(jsonSt2);
Object modelObject = jsonModelObject.get("model");
if (modelObject instanceof JSONArray) {
JSONArray itemsArray =(JSONArray) modelObject;
for (int index = 0; index < itemsArray.length(); index++) {
    Model model = new Model();
    JSONObject modelItereative = (JSONObject) itemsArray.get(index);
    model.setSyscall_1(modelItereative.getString("syscall_1"));
    model.setSyscall_2(modelItereative.getString("syscall_1"));
    models.add(model);
}
}else if(modelObject instanceof JSONObject){
Model model = new Model();
JSONObject modelItereative = (JSONObject) modelObject;
model.setSyscall_1(modelItereative.getString("syscall_1"));
model.setSyscall_2(modelItereative.getString("syscall_1"));
models.add(model);
}
for(Model d22:models){
    System.out.println(d22.getSyscall_1() + " " + d22.getSyscall_2());
}

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