etl/src/main/java/com/orientechnologies/orient/etl/util/OFileManager.java
public static ODocument buildJsonFromFile(String filePath) throws IOException {

    if (filePath == null) {
      return null;
    }

    File jsonFile = new File(filePath);
    if (!jsonFile.exists()) {
      return null;
    }

    FileInputStream is = new FileInputStream(jsonFile);
    BufferedReader rd = new BufferedReader(new InputStreamReader(is, Charset.forName("UTF-8")));
    ODocument json = new ODocument();
    String jsonText = OFileManager.readAllTextFile(rd);
    json.fromJSON(jsonText, "noMap");
    return json;

  }
public static ODocument buildJsonFromFile(String filePath) throws IOException {

    if (filePath == null) {
      return null;
    }

    File jsonFile = new File(filePath);
    if (!jsonFile.exists()) {
      return null;
    }

    FileInputStream is = new FileInputStream(jsonFile);
    BufferedReader rd = new BufferedReader(new InputStreamReader(is, Charset.forName("UTF-8")));
    ODocument json = new ODocument();
    String jsonText = OFileManager.readAllTextFile(rd);
    json.fromJSON(jsonText, "noMap");
    return json;

  }
It returns a ODocument starting from a json file.

@param filePath

@return ODocument (null if the file does not exist or problem are encountered during the reading)