Examples / Google Cloud Examples / Cloud Vision Web App Hello World

Cloud Vision Web App Hello World

example java google-cloud app-engine cloud-vision

This is a web app that uses Google Cloud Vision to analyze an image uploaded by the user.

View the code for this project here.

Download the code as a .zip from DownGit here.

file input

image uploaded

pom.xml

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

<project xmlns="http://maven.apache.org/POM/4.0.0"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
  <modelVersion>4.0.0</modelVersion>

  <groupId>io.happycoding</groupId>
  <artifactId>cloud-vision-hello-world-webapp</artifactId>
  <version>1</version>

  <properties>
    <!-- Java 11 -->
    <maven.compiler.source>11</maven.compiler.source>
    <maven.compiler.target>11</maven.compiler.target>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    <jetty.version>9.4.31.v20200723</jetty.version>

    <!-- Project-specific properties -->
    <exec.mainClass>io.happycoding.ServerMain</exec.mainClass>
    <googleCloudProjectId>happy-coding-gcloud</googleCloudProjectId>
  </properties>

  <dependencies>
    <!-- Java Servlets API -->
    <dependency>
      <groupId>javax.servlet</groupId>
      <artifactId>javax.servlet-api</artifactId>
      <version>4.0.1</version>
    </dependency>
    
    <!-- Google Cloud Storage -->
    <dependency>
      <groupId>com.google.cloud</groupId>
      <artifactId>google-cloud-storage</artifactId>
      <version>1.113.0</version>
    </dependency>
    
    <!-- Google Cloud Vision -->
    <dependency>
      <groupId>com.google.cloud</groupId>
      <artifactId>google-cloud-vision</artifactId>
      <version>1.100.0</version>
    </dependency>

    <!-- Jetty -->
    <dependency>
      <groupId>org.eclipse.jetty</groupId>
      <artifactId>jetty-server</artifactId>
      <version>${jetty.version}</version>
    </dependency>
    <dependency>
      <groupId>org.eclipse.jetty</groupId>
      <artifactId>jetty-annotations</artifactId>
      <version>${jetty.version}</version>
    </dependency>

  </dependencies>

  <build>
    <plugins>
      <!-- Copy static resources like html files into the output jar file. -->
      <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-resources-plugin</artifactId>
        <version>2.7</version>
        <executions>
          <execution>
            <id>copy-web-resources</id>
            <phase>compile</phase>
            <goals><goal>copy-resources</goal></goals>
            <configuration>
              <outputDirectory>
                ${project.build.directory}/classes/META-INF/resources
              </outputDirectory>
              <resources>
                <resource><directory>./src/main/webapp</directory></resource>
              </resources>
            </configuration>
          </execution>
        </executions>
      </plugin>

      <!-- Package everything into a single executable jar file. -->
      <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-shade-plugin</artifactId>
        <version>3.2.4</version>
        <executions>
          <execution>
            <phase>package</phase>
            <goals><goal>shade</goal></goals>
            <configuration>
              <createDependencyReducedPom>false</createDependencyReducedPom>
              <transformers>
                <transformer implementation="org.apache.maven.plugins.shade.resource.ManifestResourceTransformer">
                  <mainClass>${exec.mainClass}</mainClass>
                </transformer>
              </transformers>
              <filters>
                <filter>
                  <artifact>*:*</artifact>
                  <!-- The Cloud Vision library signs its jar, so exclude its signature in the output jar -->
                  <excludes>
                    <exclude>META-INF/*.SF</exclude>
                    <exclude>META-INF/*.DSA</exclude>
                    <exclude>META-INF/*.RSA</exclude>
                  </excludes>
                </filter>
              </filters>
            </configuration>
          </execution>
        </executions>
      </plugin>
      
      <!-- App Engine plugin for deploying to the live site. -->
      <plugin>
        <groupId>com.google.cloud.tools</groupId>
        <artifactId>appengine-maven-plugin</artifactId>
        <version>2.2.0</version>
        <configuration>
          <projectId>${googleCloudProjectId}</projectId>
          <version>1</version>
        </configuration>
      </plugin>
    </plugins>
  </build>
</project>

app.yaml

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

ServerMain.java

ServerMain.java is the main class that sets up the server.

package io.happycoding;

import java.net.URL;
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();
    server.setHandler(webAppContext);

    // Load static content from inside the jar file.
    URL webAppDir =
        ServerMain.class.getClassLoader().getResource("META-INF/resources");
    webAppContext.setResourceBase(webAppDir.toURI().toString());

    // 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)
    webAppContext.setAttribute(
        "org.eclipse.jetty.server.webapp.ContainerIncludeJarPattern", 
        ".*/target/classes/|.*\\.jar");

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

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

    // Keep the main thread alive while the server is running.
    server.join();
  }
}

ImageAnalysisServlet.java

ImageAnalysisServlet.java is a Java servlet that handles the file upload, sends the request for image analysis, and outputs some HTML content.

package io.happycoding.servlets;

import com.google.cloud.storage.Blob;
import com.google.cloud.storage.BlobId;
import com.google.cloud.storage.BlobInfo;
import com.google.cloud.storage.Storage;
import com.google.cloud.storage.StorageOptions;
import com.google.cloud.vision.v1.AnnotateImageRequest;
import com.google.cloud.vision.v1.AnnotateImageResponse;
import com.google.cloud.vision.v1.BatchAnnotateImagesResponse;
import com.google.cloud.vision.v1.EntityAnnotation;
import com.google.cloud.vision.v1.Feature;
import com.google.cloud.vision.v1.Image;
import com.google.cloud.vision.v1.ImageAnnotatorClient;
import com.google.protobuf.ByteString;
import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.util.ArrayList;
import java.util.List;
import javax.servlet.ServletException;
import javax.servlet.annotation.MultipartConfig;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.Part;

@MultipartConfig
@WebServlet("/image-analysis")
public class ImageAnalysisServlet extends HttpServlet {

  @Override
  public void doPost(HttpServletRequest request, HttpServletResponse response) throws IOException, ServletException {

    // Get the file chosen by the user
    Part filePart = request.getPart("image");
    String fileName = filePart.getSubmittedFileName();
    InputStream fileInputStream = filePart.getInputStream();
    byte[] imageBytes = fileInputStream.readAllBytes();

    // Upload the file to Cloud Storage and get its URL
    String imageUrl = uploadToCloudStorage(fileName, imageBytes);

    // Ask Cloud Vision for the labels from the image
    List<EntityAnnotation> imageLabels = getImageLabels(imageBytes);

    // Output some HTML that shows the image and its labels
    // A real codebase would probably store these in Datastore
    response.setContentType("text/html");
    PrintWriter out = response.getWriter();
    
    // Show the image
    out.println("<p>Here's the image you uploaded:</p>");
    out.println("<a href=\"" + imageUrl + "\">");
    out.println("<img src=\"" + imageUrl + "\" />");
    out.println("</a>");
    
    // Show the image's labels
    out.println("<p>Here are the labels we extracted:</p>");
    out.println("<ul>");
    for(EntityAnnotation label : imageLabels){
      out.println("<li>" + label.getDescription() + " " + label.getScore());
    }
    out.println("</ul>");
  }

  /**
   * Uses Google Cloud Vision to generate a list of labels that apply to the image
   * represented by the binary data stored in imgBytes.
   */
  private List<EntityAnnotation> getImageLabels(byte[] imgBytes) throws IOException {
    ByteString byteString = ByteString.copyFrom(imgBytes);
    Image image = Image.newBuilder().setContent(byteString).build();

    // Create a label detection request for the image
    Feature feature = Feature.newBuilder().setType(Feature.Type.LABEL_DETECTION).build();
    AnnotateImageRequest request =
        AnnotateImageRequest.newBuilder().addFeatures(feature).setImage(image).build();
    List<AnnotateImageRequest> requests = new ArrayList<>();
    requests.add(request);

    // Send the request and get the response
    ImageAnnotatorClient client = ImageAnnotatorClient.create();
    BatchAnnotateImagesResponse batchResponse = client.batchAnnotateImages(requests);
    client.close();
    List<AnnotateImageResponse> imageResponses = batchResponse.getResponsesList();
    AnnotateImageResponse imageResponse = imageResponses.get(0);

    // Handle errors
    if (imageResponse.hasError()) {
      System.err.println("Error getting image labels: " + imageResponse.getError().getMessage());
      return null;
    }

    // Return the labels extracted from the image
    return imageResponse.getLabelAnnotationsList();
  }

  /** Uploads a file to Cloud Storage and returns the uploaded file's URL. */
  private static String uploadToCloudStorage(String fileName, byte[] fileBytes) {
    String projectId = "happy-coding-gcloud";
    String bucketName = "happy-coding-gcloud.appspot.com";
    Storage storage =
        StorageOptions.newBuilder().setProjectId(projectId).build().getService();
    BlobId blobId = BlobId.of(bucketName, fileName);
    BlobInfo blobInfo = BlobInfo.newBuilder(blobId).build();
    Blob blob = storage.create(blobInfo, fileBytes);
    return blob.getMediaLink();
  }
}

index.html

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

<!DOCTYPE html>
<html>
  <head>
    <meta charset="UTF-8">
    <title>Image Upload Analysis</title>
  </head>
  <body>
    <h1>Image Upload Analysis</h1>

    <form method="POST" enctype="multipart/form-data" action="/image-analysis">
      <p>Upload an image:</p>
      <input type="file" name="image">
      <br/><br/>
      <button>Submit</button>
    </form>
  </body>
</html>

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:

file input

image uploaded

Learn more in these tutorials: