Use java.util.Base64 in Java 8+ only, to remove javax.xml.bind dependency in javase, which doesn't exist by default in Java 9

javase/src/main/java/com/google/zxing/client/j2se/Base64Decoder.java

@@ -0,0 +1,47 @@
+/*
+ * Copyright 2016 ZXing authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.google.zxing.client.j2se;
+
+/**
+ * Abstraction over Base 64 decoding implementations that work across Java versions.
+ */
+abstract class Base64Decoder {
+
+  private static final Base64Decoder INSTANCE;
+  static {
+    Base64Decoder instance;
+    try {
+      Class.forName("java.util.Base64");
+      // If succeeds, then:
+      instance = new Java8Base64Decoder();
+    } catch (ClassNotFoundException cnfe) {
+      instance = new JAXBBase64Decoder();
+    }
+    INSTANCE = instance;
+  }
+
+  /**
+   * @param s Base-64 encoded string
+   * @return bytes that the string encodes
+   */
+  abstract byte[] decode(String s);
+
+  static Base64Decoder getInstance() {
+    return INSTANCE;
+  }
+
+}

javase/src/main/java/com/google/zxing/client/j2se/ImageReader.java

@@ -17,7 +17,6 @@
 package com.google.zxing.client.j2se;
 
 import javax.imageio.ImageIO;
-import javax.xml.bind.DatatypeConverter;
 import java.awt.image.BufferedImage;
 import java.io.ByteArrayInputStream;
 import java.io.IOException;
@@ -63,7 +62,7 @@ public final class ImageReader {
     }
     String base64DataEncoded = uriString.substring(base64Start + BASE64TOKEN.length());
     String base64Data = URLDecoder.decode(base64DataEncoded, "UTF-8");
-    byte[] imageBytes = DatatypeConverter.parseBase64Binary(base64Data);
+    byte[] imageBytes = Base64Decoder.getInstance().decode(base64Data);
     return ImageIO.read(new ByteArrayInputStream(imageBytes));
   }
 

javase/src/main/java/com/google/zxing/client/j2se/JAXBBase64Decoder.java

@@ -0,0 +1,36 @@
+/*
+ * Copyright 2016 ZXing authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.google.zxing.client.j2se;
+
+import java.lang.reflect.InvocationTargetException;
+
+/**
+ * Uses {@code javax.xml.bind.DatatypeConverter}, which is not (necessarily) present
+ * in Java 9.
+ */
+final class JAXBBase64Decoder extends Base64Decoder {
+  @Override
+  byte[] decode(String s) {
+    try {
+      return (byte[]) Class.forName("javax.xml.bind.DatatypeConverter")
+          .getMethod("parseBase64Binary", String.class).invoke(null, s);
+    } catch (IllegalAccessException | InvocationTargetException |
+             NoSuchMethodException | ClassNotFoundException e) {
+      throw new IllegalStateException(e);
+    }
+  }
+}

javase/src/main/java/com/google/zxing/client/j2se/Java8Base64Decoder.java

@@ -0,0 +1,37 @@
+/*
+ * Copyright 2016 ZXing authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.google.zxing.client.j2se;
+
+import java.lang.reflect.InvocationTargetException;
+
+/**
+ * Uses {@code java.util.Base64}, available in Java 8 and later
+ */
+final class Java8Base64Decoder extends Base64Decoder {
+  @Override
+  byte[] decode(String s) {
+    try {
+      Object decoder = Class.forName("java.util.Base64")
+          .getMethod("getDecoder").invoke(null);
+      return (byte[]) Class.forName("java.util.Base64.Decoder")
+          .getMethod("decode", String.class).invoke(decoder, s);
+    } catch (IllegalAccessException | InvocationTargetException |
+             NoSuchMethodException | ClassNotFoundException e) {
+      throw new IllegalStateException(e);
+    }
+  }
+}