Convert returned JSON string to JSONArray
I have a web service that makes a database request, converts the result set to a JSON string, and returns a binding to the client. This is the code for the converter (I got it from http://biercoff.com/nice-and-simple-converter-of-java-resultset-into-jsonarray-or-xml/ ):
public static String convertToJSON(ResultSet resultSet)
throws Exception {
JSONArray jsonArray = new JSONArray();
while (resultSet.next()) {
int total_rows = resultSet.getMetaData().getColumnCount();
JSONObject obj = new JSONObject();
for (int i = 0; i < total_rows; i++) {
obj.put(resultSet.getMetaData().getColumnLabel(i + 1)
.toLowerCase(), resultSet.getObject(i + 1));
}
jsonArray.add(obj);
}
return jsonArray.toJSONString();
}
In the client application, when I print the returned string, it is in the following format:
[{"Column1":0.333333,"Column2":"FirmA"},{"Column1":0.666667,"Column2":"FirmB"}]
so far so good. The problem I am facing is converting the returned string to a JSON array. I've tried this:
JSONArray arr = new JSONArray(JSON_STRING);
but received the following error message: The JSONArray constructor in the JSONArray class cannot be applied to the given types. I tried to convert the JSON object first like this:
JSONObject obj = new JSONObject(JSON_STRING);
but got the following error: Incompatible types: String cannot be converted to Map. What am I doing wrong? Thank.
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Apparently the problem was with the json library I was using. When i used
import org.json.JSONArray;
everything worked out well. I was able to convert the returned string to an array using
JSONArray arr = new JSONArray(JSON_STRING);
and for iterating over the values I used, the code given in this answer: Accessing the elements of elements in a JSONArray from Java , which I reproduce here for simplicity:
for (int i = 0; i < arr.length(); ++i) {
JSONObject rec = arr.getJSONObject(i);
int id = rec.getInt("id");
String loc = rec.getString("loc");
// ...
}
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well you need to do it this way, for example
String jsonText = "[0,{\"1\":{\"2\":{\"3\":{\"4\":[5,{\"6\":7}]}}}}]";
try {
JSONArray array = new JSONArray(jsonText);
System.out.println(array);
System.out.println(array.length());
} catch (Exception e) {
// TODO: handle exception
e.printStackTrace();
}
}
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Check if the library used is correct. The confusion is that org.json.simple is often suggested by the IDE as the default for JSONObject and JSONArray .
You can find a link to the latest jar for the org.json library above.
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