Added QR code generator for device flow

pom.xml

@@ -118,6 +118,12 @@
             <artifactId>bcprov-jdk18on</artifactId>
             <version>1.78.1</version>
         </dependency>
+        <!-- https://mvnrepository.com/artifact/com.google.zxing/javase -->
+        <dependency>
+            <groupId>com.google.zxing</groupId>
+            <artifactId>javase</artifactId>
+            <version>3.5.3</version>
+        </dependency>
         <dependency>
             <groupId>org.projectlombok</groupId>
             <artifactId>lombok</artifactId>

src/main/java/oidc/manage/ServiceProviderTranslation.java

@@ -22,6 +22,9 @@
  */
 public class ServiceProviderTranslation {
 
+    private ServiceProviderTranslation() {
+    }
+
     public static String translateServiceProviderEntityId(String entityId) {
         return entityId.replace("@", "@@").replaceAll(":", "@");
     }

src/main/java/oidc/qr/QRCode.java

@@ -0,0 +1,12 @@
+package oidc.qr;
+
+import lombok.AllArgsConstructor;
+import lombok.Getter;
+
+@Getter
+@AllArgsConstructor
+public class QRCode {
+
+    private String url;
+    private String image;
+}

src/main/java/oidc/qr/QRGenerator.java

@@ -0,0 +1,28 @@
+package oidc.qr;
+
+import com.google.zxing.BarcodeFormat;
+import com.google.zxing.MultiFormatWriter;
+import com.google.zxing.client.j2se.MatrixToImageWriter;
+import com.google.zxing.common.BitMatrix;
+import lombok.SneakyThrows;
+
+import java.io.ByteArrayOutputStream;
+import java.util.Base64;
+
+public class QRGenerator {
+
+    private static final int IMAGE_SIZE = 400;
+
+    private QRGenerator() {
+    }
+
+    @SneakyThrows
+    public static QRCode qrCode(String url) {
+        BitMatrix matrix = new MultiFormatWriter().encode(url, BarcodeFormat.QR_CODE, IMAGE_SIZE, IMAGE_SIZE);
+        ByteArrayOutputStream bos = new ByteArrayOutputStream();
+        MatrixToImageWriter.writeToStream(matrix, "png", bos);
+        //<img src="data:image/png;base64,iVBORw0KGgoA....>
+        String image = Base64.getEncoder().encodeToString(bos.toByteArray()); // base64 encode
+        return new QRCode(url, image);
+    }
+}

src/test/java/oidc/manage/ServiceProviderTranslationTest.java

@@ -18,7 +18,7 @@ public void translateServiceProviderEntityId() {
         s = ServiceProviderTranslation.translateServiceProviderEntityId(originalSPEntityID);
         assertEquals(s, "https@//test@@@@@@test", s);
 
-        s = new ServiceProviderTranslation().translateClientId(s);
+        s = ServiceProviderTranslation.translateClientId(s);
         assertEquals(originalSPEntityID, s);
     }
 
@@ -27,7 +27,7 @@ public void translateClientId() {
         String s = ServiceProviderTranslation.translateClientId("https@//test");
         assertEquals("https://test", s);
 
-        s = new ServiceProviderTranslation().translateClientId("https@//test@@test");
+        s = ServiceProviderTranslation.translateClientId("https@//test@@test");
         assertEquals(s, "https://test@test", s);
     }
 }

src/test/java/oidc/qr/QRGeneratorTest.java

@@ -0,0 +1,37 @@
+package oidc.qr;
+
+import com.google.zxing.BinaryBitmap;
+import com.google.zxing.MultiFormatReader;
+import com.google.zxing.Result;
+import com.google.zxing.client.j2se.BufferedImageLuminanceSource;
+import com.google.zxing.common.HybridBinarizer;
+import lombok.SneakyThrows;
+import org.junit.jupiter.api.Test;
+
+import javax.imageio.ImageIO;
+import java.io.ByteArrayInputStream;
+import java.util.Base64;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+class QRGeneratorTest {
+
+    @SneakyThrows
+    @Test
+    void qrCode() {
+        String url = "https://surf.nl";
+        QRCode qrCode = QRGenerator.qrCode(url);
+        assertEquals(url, qrCode.getUrl());
+        //Because we can
+        byte[] decoded = Base64.getDecoder().decode(qrCode.getImage());
+        BinaryBitmap binaryBitmap = new BinaryBitmap(
+                new HybridBinarizer(new BufferedImageLuminanceSource(ImageIO.read(new ByteArrayInputStream(decoded)))));
+        int height = binaryBitmap.getHeight();
+        int width = binaryBitmap.getWidth();
+        assertEquals(400, width);
+        assertEquals(400, height);
+
+        Result result = new MultiFormatReader().decode(binaryBitmap);
+        assertEquals(url, result.getText());
+    }
+}