如何在java中將json數據轉換為字符串

Question

我想將json數據轉換為字符串

import java.io.BufferedReader;
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;
import org.json.JSONArray;
import org.json.JSONObject;
public static void main(String[] args) throws Exception
{

    URL url = new URL("http://192.168.1.13/test/ProductWb.php?productId=9");
    HttpURLConnection conn ;
    conn = (HttpURLConnection) url.openConnection();
    conn.setRequestMethod("GET");
    conn.setReadTimeout(60);
    conn.setRequestProperty("Accept", "application/json");
    String json="";

    json = readUrl(conn);
           System.out.println(json);
           JSONObject jsonObject=new JSONObject(json);
           JSONArray jarray=jsonObject.getJSONArray("modeles");
           JSONObject  modele= jarray.getJSONObject("modele");
           for (int i=0;i<modele.length();i++) {
               System.out.println(modele(i).getString("id_product"));
                System.out.println(modele(i).getString("meta_title"));
                System.out.println("*********");
              }


}

它向我展示了 json 數據，但給了我這個錯誤：

{"modeles":[{"modele":{"id_product":"9","id_shop":"1","id_lang":"4","description":null,"description_short":"<pre>Peugeot 208<\/pre>","info_prix":"","info_1":null,"info_2":null,"info_3":null,"info_4":null,"info_5":null,"link_rewrite":"208","meta_description":"Peugeot 208","meta_keywords":"peugeot 208","meta_title":"Peugeot 208","name":"208","available_now":"","available_later":""}}]}
Exception in thread "main" java.lang.IllegalStateException: This is not a JSON Array.
at com.google.gson.JsonElement.getAsJsonArray(JsonElement.java:106)
at com.autoreduc.services.TestProduct.main(TestProduct.java:59)

如果您有任何解決方案，請幫助我。 提前致謝

Answer 1

您的 JSON 不是數組。

它是一個 JSON 對象，具有一個屬性： modeles ，其值為數組。

將根解析為JsonObject 。

Answer 2

您可以使用 ObjectMapper 將對象轉換為 json 字符串：

ObjectMapper mapper = new ObjectMapper();
try {
  String json = mapper.writeValueAsString(cat);
  System.out.println("ResultingJSONstring = " + json);
  //System.out.println(json);
} catch (JsonProcessingException e) {
   e.printStackTrace();
}

Answer 3

{ -> 代表 JSONObject 和[ -> 代表 JSONArray，先獲取 jsonObject 再獲取其中的數組。

我嘗試使用jsonObject包導入 jar

 JSONObject jsonObject=new JSONObject(yourstring);
    JSONArray jarray=jsonObject.getJSONArray("modeles");
 JSONObject  modele= jarray.getJSONObject("modele");
   for (int i=0;i<modele.length();i++) {
       System.out.println(modele(i).getString("id_product"));
        System.out.println(modele(i).getString("meta_title"));
        System.out.println("*********");
      }

Answer 4

在您的代碼中，您從 URL 讀取 json 數據。 我只是復制了您的數據並將其粘貼到一個文件中，然后在您的 url 關閉時讀取了該文件。 在這里，我一步一步地展示了如何解析您的 json 對象和其中的內容。 為此，我使用了java-json-schema.jar 。

    import java.io.FileNotFoundException;
    import java.io.FileReader;
    import java.io.IOException;
    import java.util.Iterator;
    import org.json.simple.JSONArray;
    import org.json.simple.JSONObject;
    import org.json.simple.parser.JSONParser;
    import org.json.simple.parser.ParseException;
    public class Tets {

        /**
         * @param args
         */
        public static void main(String[] args) {
            // TODO Auto-generated method stub
            JSONParser parser = new JSONParser();
           try{
          /*  URL url = new URL("http://192.168.1.13/test/ProductWb.php?productId=9");
            HttpURLConnection conn ;
            conn = (HttpURLConnection) url.openConnection();
            conn.setRequestMethod("GET");
            conn.setReadTimeout(60);
            conn.setRequestProperty("Accept", "application/json");*/
            String json="";

            Object obj = parser.parse(new FileReader("C:\\XXX\\XX\\src\\javapackage\\t.json"));

            JSONObject jsonObject = (JSONObject) obj;
            System.out.println(jsonObject.toJSONString());  //modeles object
            JSONArray name = (JSONArray) jsonObject.get("modeles");
            System.out.println(name.toJSONString());//array inside modeles array


            for (Object o : name)
              {
                JSONObject person = (JSONObject) o;
                 JSONObject person1 = (JSONObject)person.get("modele");
                              System.out.println(person.get("modele"));//modele object
                              System.out.println(person1.get("id_lang"));//modele attribute
              } 



        }catch(Exception e){e.printStackTrace();}

        }
    }

輸出

你的 Json 對象

{"modeles":[{"modele":{"id_lang":"4","info_5":null,"info_4":null,"link_rewrite":"208","meta_keywords":"peugeot 208","info_3":null,"info_2":null,"info_1":null,"available_now":"","meta_description":"Peugeot 208","id_product":"9","description_short":"<pre>Peugeot 208<\/pre>","description":null,"name":"208","info_prix":"","meta_title":"Peugeot 208","available_later":"","id_shop":"1"}}]}

您包含在 json 對象中的 Json 數組

[{"modele":{"id_lang":"4","info_5":null,"info_4":null,"link_rewrite":"208","meta_keywords":"peugeot 208","info_3":null,"info_2":null,"info_1":null,"available_now":"","meta_description":"Peugeot 208","id_product":"9","description_short":"<pre>Peugeot 208<\/pre>","description":null,"name":"208","info_prix":"","meta_title":"Peugeot 208","available_later":"","id_shop":"1"}}]

你在數組中的 Json 對象

{"id_lang":"4","info_5":null,"info_4":null,"link_rewrite":"208","meta_keywords":"peugeot 208","info_3":null,"info_2":null,"info_1":null,"available_now":"","meta_description":"Peugeot 208","id_product":"9","description_short":"<pre>Peugeot 208<\/pre>","description":null,"name":"208","info_prix":"","meta_title":"Peugeot 208","available_later":"","id_shop":"1"}

你的 Json 對象 id_lang 屬性值 = 4

4