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.

Note: Please go through the code given in this section to ensure you fully understand it. We will discuss the architecture of the function and the client in the next section.

ToDoList.java
copy

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.fasterxml.jackson.databind.ObjectMapper;
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());
@SuppressWarnings("unchecked")
@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"));

            ArrayList&lt;ZCRowObject&gt; rowList = ZCQL.getInstance().executeQuery("SELECT COUNT(ROWID) FROM TodoItems");
            Integer totalTodos = Integer.parseInt(new ObjectMapper().writeValueAsString(rowList.get(0).get("TodoItems", "COUNT(ROWID)")));
            Boolean hasMore = totalTodos &gt; page * perPage;

            ArrayList&lt;HashMap&lt;String, String&gt;&gt; todoItems = new ArrayList&lt;&gt;();
            ZCQL.getInstance().executeQuery(String.format("SELECT ROWID, Notes FROM TodoItems LIMIT %d, %d",
                    (page - 1) * perPage, perPage)).forEach(row -&gt; {
                HashMap&lt;String, String&gt; item = new HashMap&lt;&gt;();
                item.put("id", row.get("TodoItems", "ROWID").toString());
                item.put("notes", row.get("TodoItems", "Notes").toString());
                todoItems.add(item);
            });

            response.setStatus(200);
            responseData.put("status", "success");
            responseData.put("data", new JSONObject() {
                {
                    put("hasMore", hasMore);
                    put("todoItems", todoItems);
                }
            });

        // POST method adds a new todo item to 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 a todo item from the Data Store by its ID.
        } else if (method.equals(DELETE) && uri.matches("/\\d+")) {
            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());
}

}

The functions directory is now configured.

Last Updated 2024-09-20 19:07:45 +0530 IST

Advanced I/O Functions Functions Directory Structure