Re: How to use json in client side

On Saturday, April 2, 2016 at 12:52:51 PM UTC+2, schmitt kevin wrote:

Hello everyone , can you help me please?

in my server wich connect with mysql databse i send to my client one json table like that 

rs = stmt.executeQuery("SELECT * FROM test");

res ="[";

while (rs.next()) {

String titre = rs.getString("id");

String auteur = rs.getString("comment");

res += "\t{\"Titre\": \""+titre+ "\",\n";

res += "\t\"Auteur\": \""+auteur+ "\",\n";

res += "\t},\n";

}

res += "]\n";

So this returns an array of objects, each object having a Titre and Auteur property; e.g.

[    {"Titre": "titre 1",

    "Auteur": "auteur 1",

    },

    {"Titre": "titre 2",

    "Auteur": "auteur 2",

    },

]

Note however that you have dangling commas inside both objects and the array, and that's not valid JSON (neither http://json.org nor http://www.ecma-international.org/ecma-262/5.1/#sec-15.12.1) so it'll likely break at parsing time.

(side note: either use a proper JSON library, or properly escape the titre and auteur values or you'll risk corrupting your output)

 

 and after i try to receive and use json data but dont work 

in my client side 

final ProjectServiceAsync getService = GWT.create(ProjectService.class);

getService.connection( new AsyncCallback<String>() 

  {

   public void onFailure(Throwable caught) 

   {

    System.out.println("error");

   }

           

   public void onSuccess(String result) 

   {

    JSONValue jsonValue = JSONParser.parseStrict(result);

    com.google.gwt.json.client.JSONObject customerObject = jsonValue.isObject();

    com.google.gwt.json.client.JSONArray jsonArray = customerObject.get("titre").isArray();

    StringBuilder builder = new StringBuilder("** Livre ** \n"); 

    builder.append(jsonArray.get(0).isObject().get("Titre").isString().stringValue()).append(" ");

    Window.alert(builder.toString());

   

    //resultTxt.setText(result);

   }

  });

}

This code expects an object at top-level with a Titre property being an array of strings; this is not what the sender produces. So even if you fix the dangling commas in the JSON produced by the server, this won't work.

Anyway, I suggest using overlay types and JsonUtils.safeEval instead of com.google.gwt.json; or even directly go with JsInterop.

final class Livre extends JavaScriptObject {

  protected Livre() {}

  public native String getTitre() /*-{ return this.Titre; }-*/;

  public native String getAuteur() /*-{ return this.Auteur; }-*/;

}

JsArray<Livre> livres = JsonUtils.safeEval(result);

for (int i = 0, l = livres.length(); i < l; i++) {

  builder.append(livres.get(i).getTitre()).append(" ");

}

 

(side note: similarly to the JSON generation on server-side, if you intend to use the 'builder' with toInnerHTML or similar, make sure you properly escape it or, better, use SafeHtml, so avoid XSS)

With JsInterop (jsinterop.annotations.*, you'd need 2.8.0-beta1 I believe), it'd be something like:

@JsType

interface Livre {

  @JsProperty(name="Titre") String getTitre();

  @JsProperty(name="Auteur") String getAuteur();

}

Livre[] livres = (Livre[]) JsonUtils.<Object>safeEval(result);

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