SEC-1764: Backport Utf8 encoder to 3.0.x

core/src/main/java/org/springframework/security/core/codec/Utf8.java

@@ -0,0 +1,42 @@
+package org.springframework.security.core.codec;
+
+import java.nio.ByteBuffer;
+import java.nio.CharBuffer;
+import java.nio.charset.CharacterCodingException;
+import java.nio.charset.Charset;
+import java.util.*;
+
+/**
+ * UTF-8 Charset encoder/decoder.
+ * <p>
+ * For internal use only.
+ *
+ * @author Luke Taylor
+ */
+public final class Utf8 {
+    private static final Charset CHARSET = Charset.forName("UTF-8");
+
+    /**
+     * Get the bytes of the String in UTF-8 encoded form.
+     */
+    public static byte[] encode(CharSequence string) {
+        try {
+            ByteBuffer bytes = CHARSET.newEncoder().encode(CharBuffer.wrap(string));
+
+            return Arrays.copyOfRange(bytes.array(), 0, bytes.limit());
+        } catch (CharacterCodingException e) {
+            throw new IllegalArgumentException("Encoding failed", e);
+        }
+    }
+
+    /**
+     * Decode the bytes in UTF-8 form into a String.
+     */
+    public static String decode(byte[] bytes) {
+        try {
+            return CHARSET.newDecoder().decode(ByteBuffer.wrap(bytes)).toString();
+        } catch (CharacterCodingException e) {
+            throw new IllegalArgumentException("Decoding failed", e);
+        }
+    }
+}