How to convert array s from JSON file to java object - json

Question

I have a JSON file with two different arrays. I need to convert it into java objects. Is there any method to do it using GSON and JSON. This is what we have tried.
package package1;
import org.json.JSONArray;
import org.json.JSONObject;
public class foo
{
public static void main(String[] args) throws Exception
{
String jsonInput = "{\"JObjects\":{\"JArray1\":[{\"A\":\"a\",\"B\":\"b\",\"C\":\"c\"},{\"A\":\"a1\",\"B\":\"b2\",\"C\":\"c3\",\"D\":\"d4\",\"E\":\"e5\"},{\"A\":\"aa\",\"B\":\"bb\",\"C\":\"cc\",\"D\":\"dd\"}]}}";
JSONObject outerObject = new JSONObject(jsonInput);
JSONObject innerObject = outerObject.getJSONObject("JObjects");
JSONArray jsonArray = innerObject.getJSONArray("JArray1");
for (int i = 0, size = jsonArray.length(); i < size; i++)
{
JSONObject objectInArray = jsonArray.getJSONObject(i);
String[] elementNames = JSONObject.getNames(objectInArray);
System.out.printf("%d ELEMENTS IN CURRENT OBJECT:\n", elementNames.length);
for (String elementName : elementNames)
{
String value = objectInArray.getString(elementName);
System.out.printf("name=%s, value=%s\n", elementName, value);
}
System.out.println();
}
}
}
PLease guide me with the code.

Answer 1

You can easily parse json objects to java objects and and vice-versa. To do so, you can use Google's framework 'gson': http://code.google.com/p/google-gson/
Maven dependency
<dependency>
<groupId>com.google.code.gson</groupId>
<artifactId>gson</artifactId>
<version>2.2.4</version>
</dependency>
EXAMPLE:
We make a java model class 'Person'. That person has a first name and a last name:
public class Person {
private String firstname;
private String lastname;
//getters and setters
...
public String toString() {
return "Person [firstname: "+ firstname + ", lastname: " + lastname + "]";
}
}
Now we can create a person object and parse it to a json string with gson:
public class PersonToJson {
public static void main(String[] args) {
Person person = new Person();
person.setFirstname("Laurent");
person.setLastname("Hinoul");
String json = gson.toJson(person);
System.out.println(json);
}
}
The output will be: {"firstname":"Laurent","lastname":"Hinoul"}
Now we can easily parse that string back to an object:
public class JsonToPerson {
public static void main(String[] args) {
final String json = "{"firstname":"Laurent","lastname":"Hinoul"}";
Gson gson = new Gson();
Person person = gson.fromJson(json, Person.class);
System.out.println(person);
}
}
The output will be: Person [firstname: Laurent, lastname: Hinoul]