json to java object custom parsers

Question

Are there any custom JSON to java object parsers to map json properties to Java object attributes through some configuration.

suppose I have class

class Person { String id; String name; String loc;}

My json String is

{name:"xy",id:12, address: {location: "abc"}}

I need map location.address of json to loc property of Person. We need to drive this mapping through config XML or prop file.

EDITED....

I am trying to have grammer or rules defined in property file such as:

address.location = loc
id = id
name = name

This is what I am thinking. Not sure how map complex types such as List, Map, etc

So my code would call a method

Person p = ObjectMapper.map(jsonData,Person.class,configuration)

and actual mapping is done is this way

class ObjectMapper {
public static <T> T map(String jsonData,Class<T> rootType, Map<String,String> rules) {

    T object = rootType.newInstance();
     // TODO: code to parse json using the rules 
     //and finally return object

    return (T) object;
}

This is what I am planning to do. Any help is appreciated. Thanks in Advance.

code.google.com/p/google-gson and more details: pragmateek.com/javajson-mapping-with-gson/… — Dan
– Dan, Commented Sep 29, 2014 at 15:00
Show us the code you have tried and describe what problems you have with it. — user1907906
– user1907906, Commented Sep 29, 2014 at 15:01

Yogesh Prajapati · Accepted Answer · 2014-09-30 09:08:10Z

2

Use following code.

import java.lang.reflect.Method;
import java.lang.reflect.Type;
import java.util.HashMap;
import java.util.Map;

import com.google.gson.Gson;
import com.google.gson.reflect.TypeToken;

public class Test {

    public static void main(String... args) throws Exception{
        Map<String, String> rules = new HashMap<>();
        rules.put("address.location", "loc");
        rules.put("name", "name");
        rules.put("id", "id");

        String jsonData = "{name:'xy',id:'12', address: {location: 'abc'}, phones: ['a', 'b', 'c']}";

        Person person = (Person) map(jsonData, Person.class, rules);
        System.out.println(new Gson().toJson(person));
    }

    public static Object map(String jsonData, Class<?> rootType, Map<String, String> rules) throws Exception{
        Map<String, Object> genericMap = new HashMap<>();
        Type type = new TypeToken<Map<String, Object>>() {}.getType();
        genericMap = new Gson().fromJson(jsonData, type);

        Object object = rootType.newInstance();

        for (Map.Entry<String, String> entry : rules.entrySet()){
            String mapKey = entry.getKey();
            String mapValue = entry.getValue();

            String keys[] = mapKey.split("\\.");
            Map<String, Object> obj = null;
            if(keys.length > 1){
                obj = (Map<String, Object>) genericMap.get(keys[0]);
                for(int i=1;i<keys.length-1;i++){
                    obj = (Map<String, Object>) obj.get(keys[i]);
                }
                // Method method = object.getClass().getDeclaredMethod("set" +  capitalize(mapValue) , String.class);
                // method.invoke(object, (String)obj.get(keys[keys.length-1]));
                Field field = object.getClass().getDeclaredField(mapValue);
                field.set(object, obj.get(keys[keys.length - 1]));
            }else{
                // Method method = object.getClass().getDeclaredMethod("set" +  capitalize(mapValue) , String.class);
                // method.invoke(object, (String)genericMap.get(mapValue));

                Field field = object.getClass().getDeclaredField(mapValue);
                field.set(object, genericMap.get(mapValue));
            }
        }
        return object;
    }

    public static  String capitalize(String line){
      return Character.toUpperCase(line.charAt(0)) + line.substring(1);
    }
}

class Person {
    String id;
    String name;
    String loc;

    public String getId() {
        return id;
    }

    public void setId(String id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getLoc() {
        return loc;
    }

    public void setLoc(String loc) {
        this.loc = loc;
    }

}

Output

{"id":"12","name":"xy","loc":"abc","phones":["a","b","c"]}

Details

Used Gson API.
This code works for n number referenced object (like a.b.c.item).
Your class should contain getter/setter for each field.
Field name of Rules and POJO should match.

edited Sep 30, 2014 at 9:08

answered Sep 30, 2014 at 8:16

Yogesh Prajapati

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3 Comments

CompuDynasty Over a year ago

Thanks for sharing the code. Would this work for even List, Map and Complex type(such as Person has some ProfessionDetails). Suppose I have a list of phone number object phoneNumber with fields exchange code, subscriber number and need map to list property of Person Object.How should I define my rules in this case. I was thinking to define like L->phonenumbers.exchangecode = L-> phonenumbers.exchangecode. L represents List. C

Yogesh Prajapati Over a year ago

currently i assuming your all fields of type String, see ("set" + capitalize(mapValue) , String.class). but you can give a datatype using reflections. i tried for List also.

Yogesh Prajapati Over a year ago

changed a code to support collections, now you have to change a parser according to your requirement. you can create your own parser depend on your requirement.

ChristopherMortensen · Accepted Answer · 2014-09-29 15:25:51Z

-1

Import this library to your project code.google.com/p/google-gson

Afterwards, it is possible to do this: ("json" is whatever json-String you want to parse in. It could be the one you specified in your question.)

Person personFromJson = new Gson().fromJson(json, Person.class);

answered Sep 29, 2014 at 15:25

ChristopherMortensen

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1 Comment

5gon12eder Over a year ago

I don't think that the OP's example can be handled that easily given that there is no 1-to-1 mapping of attributes.

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