Configure the Advanced I/O Function
Let’s begin coding the Alien City application by configuring the function component.
The Java function directory ( functions/AlienCityAIO ) contains the following files:
- The AlienCityAIO.java main function file
- The catalyst-config.json configuration file
- Java library files in the lib folder
- .classpath and .project dependency files
You will be adding code in the AlienCityAIO.java main function file.
The two APIs in the Advanced I/O function that handle the routing between the server and the Data Store are:
- GET /alien: To check whether aliens are present in a city
- POST /alien: To report an alien presence in a city
Let’s now add the code in the function file.
Copy the code given below and paste it in AlienCityAIO.java in the functions/AlienCityAIO directory of your project, and save the file. You can use any IDE of your choice to work with the application’s files.
AlienCityAIO.javacopyimport java.io.InputStreamReader; import java.util.ArrayList; import java.util.logging.Level; import java.util.logging.Logger; import javax.servlet.ServletInputStream; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import com.catalyst.advanced.CatalystAdvancedIOHandler; import com.zc.component.object.ZCObject; import com.zc.component.object.ZCRowObject; import com.zc.component.zcql.ZCQL; import org.json.simple.JSONObject; import org.json.simple.parser.JSONParser; public class AlienCityAIO implements CatalystAdvancedIOHandler { private static final Logger LOGGER = Logger.getLogger(AlienCityAIO.class.getName()); private static String TABLENAME = "AlienCity"; private static String COLUMNNAME = "CityName"; JSONObject responseData = new JSONObject(); static String GET = "GET"; static String POST = "POST"; @Override @SuppressWarnings("unchecked") public void runner(HttpServletRequest request, HttpServletResponse response) throws Exception { try { //Fetches the endpoint and method to which the call was made String url = request.getRequestURI(); String method = request.getMethod(); //The GET API that checks the table for an alien encounter in that city if ((url.equals("/alien")) && method.equals(GET)) { String cityName = request.getParameter("city_name"); //Queries the Catalyst Data Store table and checks whether a row is present for the given city int length = getAlienCountFromCatalystDataStore(cityName); if (length > 0) { responseData.put("message", "Uh oh! Looks like there are aliens in this city!"); responseData.put("signal", "positive"); } else { responseData.put("message", "Hurray! No alien encounters in this city yet!"); responseData.put("signal", "negative"); } } //The POST API that reports the alien encounter for a particular city else if ((url.equals("/alien")) && method.equals(POST)) { //Gets the request body and parses it ServletInputStream requestBody = request.getInputStream(); JSONParser jsonParser = new JSONParser(); JSONObject jsonObject = (JSONObject) jsonParser.parse(new InputStreamReader(requestBody, "UTF-8")); String cityName = (String) jsonObject.get("city_name"); //Queries the Catalyst Data Store table and checks whether a row is present for the given city int length = getAlienCountFromCatalystDataStore(cityName); if (length > 0) { responseData.put("message", "Looks like you are not the first person to encounter aliens in this city! Someone has already reported an alien encounter here!"); } //If the row is not present, then a new row is inserted else { ZCRowObject row = ZCRowObject.getInstance(); row.set("CityName", cityName); ZCObject.getInstance().getTableInstance(TABLENAME).insertRow(row); responseData.put("message", "Thanks for reporting!"); } } else { //The actions are logged. You can check the logs from Catalyst Logs. LOGGER.log(Level.SEVERE, "Error. Invalid Request"); responseData.put("error", "Request Endpoint not found"); response.setStatus(404); } //Sends the response back to the Client response.setContentType("application/json"); response.getWriter().write(responseData.toString()); response.setStatus(200); } catch (Exception e) { //The actions are logged. You can check the logs from Catalyst Logs. LOGGER.log(Level.SEVERE, "Exception in AlienCityAIO", e); responseData.put("error", "Internal server error occurred. Please try again in some time."); response.getWriter().write(responseData.toString()); response.setStatus(500); } } /** * Checks whether an alien encounter is already reported for the given city by * querying the Data Store table * * @param {*} catalystApp * @param {*} cityName */ private int getAlienCountFromCatalystDataStore(String cityName) throws Exception { String query = "select * from " + TABLENAME + " where " + COLUMNNAME + " = " + cityName; //Gets the ZCQL instance and executes query using the query string ArrayList
rowList = ZCQL.getInstance().executeQuery(query); return rowList.size(); } } The functions directory is now configured. We will discuss the architecture of the function and the client in the next section.
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