Natural Language Web App Hello World

Natural Language Web App Hello World

September 27, 2020

example java google-cloud app-engine natural-language sentiment-analysis

This is a web app that uses Google Cloud Natural Language to analyze some text uploaded by the user.

View the code for this project here.

Download the code as a .zip from DownGit here.

text input

sentiment analysis


pom.xml is a Maven POM file that defines the project.

<project xmlns=""


    <!-- Java 11 -->

    <!-- Project-specific properties -->

    <!-- Java Servlets API -->

    <!-- Google Cloud Natural Language -->

    <!-- Jetty -->

      <!-- Copy static resources like html files into the output jar file. -->

      <!-- Package everything into a single executable jar file. -->
                <transformer implementation="org.apache.maven.plugins.shade.resource.ManifestResourceTransformer">
                  <!-- The Cloud Natural Language library signs its jar, so exclude its signature in the output jar -->

      <!-- App Engine plugin for deploying to the live site. -->


app.yaml is a config file that sets up App Engine. This hello world project only uses a single property that sets the runtime to Java 11.

runtime: java11 is the main class that sets up the server.

package io.happycoding;

import org.eclipse.jetty.annotations.AnnotationConfiguration;
import org.eclipse.jetty.server.Handler;
import org.eclipse.jetty.server.handler.DefaultHandler;
import org.eclipse.jetty.server.Server;
import org.eclipse.jetty.servlet.DefaultServlet;
import org.eclipse.jetty.webapp.Configuration;
import org.eclipse.jetty.webapp.WebAppContext;
import org.eclipse.jetty.webapp.WebInfConfiguration;

 * Starts up the server, including a DefaultServlet that handles static files,
 * and any servlet classes annotated with the @WebServlet annotation.
public class ServerMain {

  public static void main(String[] args) throws Exception {

    // Create a server that listens on port 8080.
    Server server = new Server(8080);
    WebAppContext webAppContext = new WebAppContext();

    // Load static content from inside the jar file.
    URL webAppDir =

    // Enable annotations so the server sees classes annotated with @WebServlet.
    webAppContext.setConfigurations(new Configuration[]{
      new AnnotationConfiguration(),
      new WebInfConfiguration(),

    // Look for annotations in the classes directory (dev server) and in the
    // jar file (live server)

    // Handle static resources, e.g. html files.
    webAppContext.addServlet(DefaultServlet.class, "/");

    // Start the server! 🚀
    System.out.println("Server started!");

    // Keep the main thread alive while the server is running.
} is a Java servlet that handles the POST request including the text entered by the user, sends the request for sentiment analysis, and outputs some HTML content.

package io.happycoding.servlets;

import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class SentimentAnalysisServlet extends HttpServlet {

  public void doPost(HttpServletRequest request, HttpServletResponse response) throws IOException {
    String message = request.getParameter("message");

    Document doc = Document.newBuilder()
    LanguageServiceClient languageService = LanguageServiceClient.create();
    Sentiment sentiment = languageService.analyzeSentiment(doc).getDocumentSentiment();
    float score = sentiment.getScore();

    // Output the sentiment score as HTML.
    // A real project would probably store the score in Datastore.
    response.getWriter().println("<h1>Sentiment Analysis</h1>");
    response.getWriter().println("<p>You entered: " + message + "</p>");
    response.getWriter().println("<p>Sentiment analysis score: " + score + "</p>");
    response.getWriter().println("<p><a href=\"/index.html\">Back</a></p>");


index.html is an HTML file that shows a form with a file input.

<!DOCTYPE html>
    <meta charset="UTF-8">
    <title>Sentiment Analysis</title>
    <h1>Sentiment Analysis</h1>
    <p>Type a message and click submit to analyze its sentiment:</p>

    <form method="POST" action="/sentiment">
      <textarea name="message"></textarea>


You can run this locally by executing this command:

mvn package exec:java

Then visit http://localhost:8080 in your web browser, and you should see this:

text input

sentiment analysis

Learn more in these tutorials:

Natural Language Examples


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