Converting json string to java object?

问题

I have been looking around for examples related to converting JSON strings to Java object but haven't found any good examples. The one I found was really basic once and not really dealing with complex JSON strings.

I am making an app to translate strings from english to different languages using google translate api. Google's response upon query is...foolowing text is formatted in JSON,

{"data":{"translations":[{"translatedText":"Bonjour tout le monde"}]}}

my approach so far is using GSON API, however, I am stuck by actually how should I manipulate this complicated result and create java object?

My java class is...

import com.google.gson.Gson;

public class JSONConverter {

private String traslatedText;

/**
 * Create an object of it self by manipulating json string
 * @param json type: String
 * @return String Translated text result from JSON responce
 */
public String getTranslation(String json){  
    Gson gson = new Gson();
    JSONConverter obj = gson.fromJson(json, JSONConverter.class);

    return obj.getTranslationForReturn();
}

/**
 * Method return a translation to a private call
 * @return String translation
 */
private String getTranslationForReturn(){
    return this.traslatedText;
 }
}

Above approach is not working since I am not getting "Bonjour tout le monde" on return,

it would be a great pleasure if someone can extend my understanding.

回答1:

EDIT: You need your java Data class to be an exact model of the JSON. So your

{"data":{"translations":[{"translatedText":"Bonjour tout le monde"}]}}

becomes:

class DataWrapper {
    public Data data;

    public static DataWrapper fromJson(String s) {
        return new Gson().fromJson(s, DataWrapper.class);
    }
    public String toString() {
        return new Gson().toJson(this);
    }
}
class Data {
    public List<Translation> translations;
}
class Translation { 
    public String translatedText;
}

As the object model gets more complicated the org.json style code veers towards unreadable whereas the gson/jackson style object mapping is still just plain java objects.

回答2:

I usually like to use the plain org.json library

Use it as:

 // make sure the quotes are escaped
String str = "{\"data\":{\"translations\":[{\"translatedText\":\"Bonjour tout le monde\"}]}}";
 // the object data is inside a "global" JSONObject
data = new JSONObject(str).getJSONObject("data");
// get a JSONArray from inside an object
JSONArray translations = data.getJSONArray("translations");
// get the first JSONObject from the array
JSONObject text = translations.getJSONObject(0);
// get the String contained in the object -> logs Bonjour tout le monde
Log.d("***>Text", text.getString("translatedText"));

Maybe so much code is less clear than what I would have liked. This is the function as I would do it:

public String getTranslation(String json){  
  JSONObject data = new JSONObject(json).getJSONObject("data");
  return data.getJSONArray("translations").getJSONObject(0).getString("translatedText");
}

回答3:

check this out Converting JSON to Java , i guess you can define a class as the object and pass that along. So, create some class and pass it along.

Data obj = gson.fromJson(json, Data.class);

class Data{
  public List<Data> getTranslation(){
     return translations;
  }
}

Try out something like that. You may need to experiment a little.

来源：https://stackoverflow.com/questions/6079505/converting-json-string-to-java-object

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java

android

json

api

gson