#18: added initial implementation that *should* work in Android environments. This still needs to be tested in a real Android project.

pom.xml

@@ -106,6 +106,22 @@
             <optional>true</optional>
         </dependency>
 
+        <!-- Provided scope: only used in Android environments - not downloaded as a transitive dependency.
+             This dependency is only a stub of the actual implementation, which means we can't use it at test time
+             during TestNG tests.  An Android environment is required to test for real. -->
+        <dependency>
+            <groupId>com.google.android</groupId>
+            <artifactId>android</artifactId>
+            <version>4.1.1.4</version>
+            <scope>provided</scope>
+            <exclusions>
+                <exclusion>
+                    <groupId>commons-logging</groupId>
+                    <artifactId>commons-logging</artifactId>
+                </exclusion>
+            </exclusions>
+        </dependency>
+
         <!-- Test Dependencies: Only required for testing when building.  Not required by users at runtime: -->
         <dependency>
             <groupId>ch.qos.logback</groupId>

src/main/java/io/jsonwebtoken/impl/Base64Codec.java

@@ -15,18 +15,40 @@
  */
 package io.jsonwebtoken.impl;
 
-import javax.xml.bind.DatatypeConverter;
+import io.jsonwebtoken.lang.Classes;
 
 public class Base64Codec extends AbstractTextCodec {
 
-    @Override
+    private static final boolean STANDARD_JVM = Classes.isAvailable("javax.xml.bind.DatatypeConverter");
+
+    private static final boolean ANDROID = Classes.isAvailable("android.util.Base64");
+
     public String encode(byte[] data) {
-        return DatatypeConverter.printBase64Binary(data);
+
+        if (STANDARD_JVM) {
+            return javax.xml.bind.DatatypeConverter.printBase64Binary(data);
+        }
+
+        if (ANDROID) {
+            int flags = android.util.Base64.NO_PADDING | android.util.Base64.NO_WRAP;
+            return android.util.Base64.encodeToString(data, flags);
+        }
+
+        throw new IllegalStateException("Unable to locate a Base64 codec for the current JVM");
     }
 
     @Override
     public byte[] decode(String encoded) {
-        return DatatypeConverter.parseBase64Binary(encoded);
+
+        if (STANDARD_JVM) {
+            return javax.xml.bind.DatatypeConverter.parseBase64Binary(encoded);
+        }
+
+        if (ANDROID) {
+            return android.util.Base64.decode(encoded, android.util.Base64.DEFAULT);
+        }
+
+        throw new IllegalStateException("Unable to locate a Base64 codec for the current JVM");
     }
 
 }