java - 将 dbcursor 对象转换为 json

Question

我有一个 java 应用程序，我想在其中将 json 数据从 servlet 发送到 jsp。我使用 mongodb 作为 Json 的数据库和 Gson 库。

我是 Java 和 Mongo 的新手。

下面是查询数据库的代码:

MongoClient mongoClient = new MongoClient("localhost", 27017);
DB database = mongoClient.getDB("MyTestDatabase");
coll = database.getCollection("players");

BasicDBObject fields = new BasicDBObject();

    fields.put("_id", 0);
    fields.put("Incident Date", 1);
    fields.put("Longitude", 1);
    fields.put("Latitude", 1);
    fields.put("Address", 1);
    fields.put("Status", 1);
    fields.put("Name", 1);

    doc.put("Address", "Mumbai");

    cursor = coll.find(doc,fields);

这是查询数据库后的结果

{ "_id" : { "$oid" : "5540cae37a104f6bbfe7c9f5"} , "Incident Date" : "30/4/2015" , "Longitude" : "77.61528809" , "Latitude" : "12.9245331" , "Address" : "Mumbai" , "Status" : "Ok" , "Name" : [ "1.ABC" , "2.XYZ" , "3.PQR"]}

我想要实现的是将上述结果转换为 JSON，并通过将结果解析为 json，使用“事件日期”、“状态”等字段访问 JSON。我试图将原始结果解析为 json，但我认为它不能像那样工作

这是我试过的。1. 将 'cursor' 转换为 ArrayList

    List<DBObject> myList = new ArrayList<DBObject>();
    myList = cursor.toArray();

1. 尝试将 ArrayList 转换为 JSON

   JSON json =new JSON();
   String serialize = json.serialize(cursor);
   

我尝试了下面的代码，但是我得到了这个错误

    JsonElement jelement = new JsonParser().parse(serialize);
    System.out.println(jelement);
    JsonObject  jobject = jelement.getAsJsonObject();//error at this line
    System.out.println(jobject);

Exception in thread "main" java.lang.IllegalStateException: Not a JSON Object: [{"_id":{"$oid":"5540cae37a104f6bbfe7c9f5"},"Incident Date":"30/4/2015","Longitude":"77.61528809","Latitude":"12.9245331","Address":"Mumbai","Status":"Ok","Culprits Name":["1.ABC","2.XYZ","3.PQR"]}]
at com.google.gson.JsonElement.getAsJsonObject(JsonElement.java:90)

谁能帮帮我？

Answer 1

遍历 cursor 并将数据推送到 JSONObject 中，然后将 jsonObject 放入 jsonarray 中，如下所示:

public JSONArray getJsonData() throws JSONException {
  JSONArray jsonarray = new JSONArray();
  BasicDBObject criteria = new BasicDBObject();
  BasicDBObject projections = new BasicDBObject();
  criteria.put("Address", "Mumbai");
  projections.put("_id", 0);
  projections.put("Incident Date", 1);
  projections.put("Longitude", 1);
  projections.put("Latitude", 1);
  projections.put("Address", 1);
  projections.put("Status", 1);
  projections.put("Name", 1);
  DBCursor cursor = coll.find(criteria, projections);
  while(cursor.hasNext()) {
    BasicDBObject obj = (BasicDBObject) cursor.next();
    jsonobj = new JSONObject();
    BasicDBList name = (BasicDBList) obj.get("Name");
    jsonobj.put("Incident Date", obj.getString("Incident Date"));
    jsonobj.put("Longitude", obj.getString("Longitude"));
    jsonobj.put("Latitude", obj.getString("Latitude"));
    jsonobj.put("Address", obj.getString("Address"));
    jsonobj.put("Status", obj.getString("Status"));
    jsonobj.put("Name", name);
    jsonarray.put(jsonobj);
  }
  return jsonarray;
}