Configure the Advanced I/O Function

Next, we will begin coding the to-do list application by configuring the function component.

The functions directory, functions/ToDoList contains:

• The ToDoList.java main function file
• The catalyst-config.json configuration file
• Java library files in the lib directory
• .classpath and .project dependency files

You will be adding code in the ToDoList.java file.

The three APIs in the Advanced I/O function that handle the routing between the server and the Data Store are:

• GET /todo: To obtain the to-do list items from the TodoItems table in the Data Store
• POST /todo: To create and save a new list item in the Data Store
• DELETE /todo: To delete a list item from the Data Store

Next, let’s add the code in the function file. Copy the Java code and paste it in ToDoList.java in the functions/TodoList directory of your project, and save the file. You can use any IDE of your choice to work with the application’s files.

    

        
ToDoList.java
        

            
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         import java.util.ArrayList;
import java.util.HashMap;
import java.util.logging.Level;
import java.util.logging.Logger;
import java.io.InputStreamReader;

import javax.servlet.ServletInputStream;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.json.simple.JSONObject;
import org.json.simple.parser.JSONParser;

import com.catalyst.advanced.CatalystAdvancedIOHandler;
import com.zc.component.object.ZCObject;
import com.zc.component.object.ZCRowObject;
import com.zc.component.object.ZCTable;
import com.zc.component.zcql.ZCQL;

public class ToDoList implements CatalystAdvancedIOHandler {
 private static final String GET = "GET";
 private static final String POST = "POST";
 private static final String DELETE = "DELETE";
 private JSONObject responseData = new JSONObject();
 private static final Logger LOGGER = Logger.getLogger(ToDoList.class.getName());

 @Override
 public void runner(HttpServletRequest request, HttpServletResponse response) throws Exception {
 	try {
 		String uri = request.getRequestURI();
 		String method = request.getMethod();
//GET method gets data from the TodoItems table in the Data Store.
 		if (method.equals(GET) && uri.equals("/all")) {
 			Integer page = Integer.parseInt(request.getParameter("page"));
 			Integer perPage = Integer.parseInt(request.getParameter("perPage"))	;
 			
 			Integer totalTodos = Integer
 					.parseInt(ZCQL.getInstance().executeQuery("SELECT COUNT(ROWID) FROM TodoItems").get(0)
 							.get("TodoItems", "ROWID").toString());
 			Boolean hasMore = totalTodos > page * perPage;

 			ArrayList> todoItems = new ArrayList>();

 			ZCQL.getInstance().executeQuery(String.format("SELECT ROWID,Notes FROM TodoItems LIMIT %d,%d",
 					(page - 1) * perPage + 1, perPage)).forEach(row -> {
 						todoItems.add(new HashMap() {
 							{
 								put("id", row.get("TodoItems", "ROWID").toString());
 								put("notes", row.get("TodoItems", "Notes").toString());
 							}
 						});
 					});
 			
 			response.setStatus(200);
 			responseData.put("status", "success");
 			responseData.put("data", new JSONObject() {
 				{
 					put("hasMore", hasMore);
 					put("todoItems", todoItems);
 				}
 			});
//POST method sends data to persist in the TodoItems table in the Data Store
 		} else if (method.equals(POST) && uri.equals("/add")) {
 			JSONParser jsonParser = new JSONParser();
 			ServletInputStream requestBody = request.getInputStream();

 			JSONObject jsonObject = (JSONObject) jsonParser.parse(new InputStreamReader(requestBody, "UTF-8"));

 			String notes = jsonObject.get("notes").toString();

 			ZCRowObject row = ZCRowObject.getInstance();
 			row.set("Notes", notes);

 			ZCRowObject todoItem = ZCObject.getInstance().getTable("TodoItems").insertRow(row);

 			response.setStatus(200);
 			responseData.put("status", "success");
 			responseData.put("data", new JSONObject() {
 				{
 					put("todoItem", new JSONObject() {
 						{
 							put("id", todoItem.get("ROWID").toString());
 							put("notes", todoItem.get("Notes").toString());
 						}
 					});

 				}
 			});
//Delete method deletes the selected items from the Data Store
 		} else if (method.equals(DELETE)) {
 			ZCTable table = ZCObject.getInstance().getTable("TodoItems");

 			table.deleteRow(Long.parseLong(uri.substring(1)));
 			
 			response.setStatus(200);
 			responseData.put("status", "success");
 			responseData.put("data", new JSONObject() {
 				{
 					put("todoItem", new JSONObject() {
 						{
 							put("id", uri.substring(1));
 						}
 					});

 				}
 			});

 		} else {
 			response.setStatus(404);
 			responseData.put("status", "failure");
 			responseData.put("message", "Please check if the URL trying to access is a correct one");
 		}
 		
 	
 	} catch (Exception e) {
 		LOGGER.log(Level.SEVERE, "Exception in Main", e);
 		responseData.put("status", "failure");
 		responseData.put("message", "We're unable to process the request.");

 	}
 	
 	response.setContentType("application/json");
 	response.getWriter().write(responseData.toString());

 }

}
    

         
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The functions directory is now configured.