Implemented deletion of comments via Datastore

portfolio/pom.xml

@@ -17,6 +17,12 @@
   </properties>
 
   <dependencies>
+    <dependency>
+      <groupId>com.google.appengine</groupId>
+      <artifactId>appengine-api-1.0-sdk</artifactId>
+      <version>1.9.59</version>
+    </dependency>
+
     <dependency>
       <groupId>javax.servlet</groupId>
       <artifactId>javax.servlet-api</artifactId>

portfolio/src/main/java/com/google/sps/servlets/DataServlet.java

@@ -14,25 +14,46 @@
 
 package com.google.sps.servlets;
 
+import com.google.appengine.api.datastore.DatastoreService;
+import com.google.appengine.api.datastore.DatastoreServiceFactory;
+import com.google.appengine.api.datastore.Entity;
+import com.google.appengine.api.datastore.FetchOptions;
+import com.google.appengine.api.datastore.Key;
+import com.google.appengine.api.datastore.PreparedQuery;
+import com.google.appengine.api.datastore.Query;
+import com.google.appengine.api.datastore.Query.SortDirection;
+import com.google.gson.Gson;
 import java.io.IOException;
+import java.util.ArrayList;
+import java.util.LinkedHashMap;
+import java.util.List;
+import java.util.Map;
 import javax.servlet.annotation.WebServlet;
 import javax.servlet.http.HttpServlet;
 import javax.servlet.http.HttpServletRequest;
 import javax.servlet.http.HttpServletResponse;
 
-import java.util.HashMap;
-// import java.util.ArrayList;
-import com.google.gson.Gson;
-
-/** Servlet that returns some example content. TODO: modify this file to handle comments data */
+/** Servlet that adds/retrieves comments stored in a Datastore */
 @WebServlet("/data")
 public class DataServlet extends HttpServlet {
-  HashMap<String, String> messages = new HashMap<String, String>();
-  // ArrayList<String> messages = new ArrayList<String>();
+  private final DatastoreService datastore = DatastoreServiceFactory.getDatastoreService();
+  private static final int DEFAULT_MAX_NUM_COMMENTS = 7;
 
   @Override
   public void doGet(HttpServletRequest request, HttpServletResponse response) throws IOException {
     response.setContentType("application/json;");
+
+    Map<String, String> messages = new LinkedHashMap<>();
+    Query query = new Query("Comment").addSort("timestamp", SortDirection.DESCENDING);
+    PreparedQuery results = datastore.prepare(query);
+
+    int maxNumComments = (int)request.getSession().getAttribute("maxNumComments");
+    for (Entity entity : results.asIterable(FetchOptions.Builder.withLimit(maxNumComments))) {
+      String username = (String) entity.getProperty("username");
+      String message = (String) entity.getProperty("message");
+      messages.put(username, message);
+    }
+
     String json = new Gson().toJson(messages);
     response.getWriter().println(json);
   }
@@ -41,8 +62,23 @@ public void doGet(HttpServletRequest request, HttpServletResponse response) thro
   public void doPost(HttpServletRequest request, HttpServletResponse response) throws IOException {
     String username = request.getParameter("username");
     String message = request.getParameter("comment-or-question");
-    messages.put(username, message);
-    // messages.add(username);
+    String maxNumCommentsString = request.getParameter("max-num-comments");
+    int maxNumComments;
+    try {
+      maxNumComments = Integer.parseInt(maxNumCommentsString);
+    } catch (NumberFormatException e) {
+      System.err.format("Could not convert to int: %s%n", maxNumCommentsString);
+      System.err.format("Using default value of %d.%n", DEFAULT_MAX_NUM_COMMENTS);
+      maxNumComments = DEFAULT_MAX_NUM_COMMENTS;
+    }
+    request.getSession().setAttribute("maxNumComments", maxNumComments);
+
+    Entity commentEntity = new Entity("Comment");
+    commentEntity.setProperty("username", username);
+    commentEntity.setProperty("message", message);
+    commentEntity.setProperty("timestamp", System.currentTimeMillis());
+
+    datastore.put(commentEntity);
     response.sendRedirect("/index.html");
   }
 }

portfolio/src/main/java/com/google/sps/servlets/DeleteServlet.java

@@ -0,0 +1,33 @@
+package com.google.sps.servlets;
+
+import com.google.appengine.api.datastore.DatastoreService;
+import com.google.appengine.api.datastore.DatastoreServiceFactory;
+import com.google.appengine.api.datastore.Entity;
+import com.google.appengine.api.datastore.Key;
+import com.google.appengine.api.datastore.PreparedQuery;
+import com.google.appengine.api.datastore.Query;
+import java.io.IOException;
+import java.util.Iterator;
+import java.util.List;
+import javax.servlet.annotation.WebServlet;
+import javax.servlet.http.HttpServlet;
+import javax.servlet.http.HttpServletRequest;
+import javax.servlet.http.HttpServletResponse;
+
+/** Servlet that deletes data from the database. */
+@WebServlet("/delete-messages")
+public class DeleteServlet extends HttpServlet {
+
+  @Override
+  public void doPost(HttpServletRequest request, HttpServletResponse response) throws IOException {
+    DatastoreService datastore = DatastoreServiceFactory.getDatastoreService();
+    Query query = new Query("Comment").setKeysOnly();
+    PreparedQuery preparedQuery = datastore.prepare(query);
+    Iterator<Entity> entities = preparedQuery.asIterator();
+    while (entities.hasNext()) {
+      Key key = entities.next().getKey();
+      datastore.delete(key);
+    }
+    response.sendRedirect("/index.html");
+  }
+}

portfolio/src/main/webapp/index.html

@@ -8,6 +8,7 @@
   </head>
   <body onload="displayMessages()">
     <div id="content">
+      <div id="opening-greeting"></div>
       <h1>Ihsan Olawale's Portfolio</h1>
       <p>This is Ihsan Olawale's portfolio.</p>
       <p>I, Ihsan Olawale, am a STEP intern at Google. By the end of the internship I will have created a web project. This is practice.</p>
@@ -20,11 +21,15 @@ <h1>Ihsan Olawale's Portfolio</h1>
       <button onclick="addRandomFact()">Learn about me</button>
       <div id="fact-container"></div>
       <form action="/data" method="POST">
-	<p>Comment here on your perception of the content. Or ask me any questions about me.</p><br/>
+	<p>Comment here on your perception of the content. Or ask me any questions about me.</p><br>
+	<input type="number" name="max-num-comments" placeholder="Max number of comments displayed"><br>
 	<input type="text" name="username" maxlength=10 value="username">
 	<textarea name="comment-or-question" rows="24" cols="80">What amazing web development this is</textarea>
-	<br/><br/>
+	<br>
+	<button onclick="deleteMessages()">Clear Comment History</button>
+	<br>
 	<input type="submit"/>
+	<br>
       </form>
       <div id="messages-container"></div>
     </div>

portfolio/src/main/webapp/script.js

@@ -59,3 +59,7 @@ function displayMessages() {
     }
   });
 }
+
+function deleteMessages() {
+  fetch('/delete-messages', {method: 'POST'}).then((response) => displayMessages());
+}