diff --git a/htrace-core/src/main/java/org/apache/htrace/Span.java b/htrace-core/src/main/java/org/apache/htrace/Span.java
index 2731583..df28630 100644
--- a/htrace-core/src/main/java/org/apache/htrace/Span.java
+++ b/htrace-core/src/main/java/org/apache/htrace/Span.java
@@ -96,6 +96,12 @@
   /**
    * Add a data annotation associated with this span
    */
+  void addKVAnnotation(String key, String value);
+
+  /**
+   * Add a data annotation associated with this span
+   */
+  @Deprecated
   void addKVAnnotation(byte[] key, byte[] value);
 
   /**
@@ -106,7 +112,7 @@
   /**
    * Get data associated with this span (read only)
    */
-  Map<byte[], byte[]> getKVAnnotations();
+  Map<String, String> getKVAnnotations();
 
   /**
    * Get any timeline annotations (read only)
@@ -140,12 +146,11 @@
         jgen.writeString(String.format("%016x", span.getParentId()));
       }
       jgen.writeEndArray();
-      Map<byte[], byte[]> traceInfoMap = span.getKVAnnotations();
+      Map<String, String> traceInfoMap = span.getKVAnnotations();
       if (!traceInfoMap.isEmpty()) {
         jgen.writeObjectFieldStart("n");
-        for (Map.Entry<byte[], byte[]> e : traceInfoMap.entrySet()) {
-          jgen.writeStringField(new String(e.getKey(), "UTF-8"),
-              new String(e.getValue(), "UTF-8"));
+        for (Map.Entry<String, String> e : traceInfoMap.entrySet()) {
+          jgen.writeStringField(e.getKey(), e.getValue());
         }
         jgen.writeEndObject();
       }
diff --git a/htrace-core/src/main/java/org/apache/htrace/impl/LocalFileSpanReceiver.java b/htrace-core/src/main/java/org/apache/htrace/impl/LocalFileSpanReceiver.java
index 7095008..8b037bf 100644
--- a/htrace-core/src/main/java/org/apache/htrace/impl/LocalFileSpanReceiver.java
+++ b/htrace-core/src/main/java/org/apache/htrace/impl/LocalFileSpanReceiver.java
@@ -16,6 +16,8 @@
  */
 package org.apache.htrace.impl;
 
+import com.fasterxml.jackson.databind.ObjectMapper;
+import com.fasterxml.jackson.databind.ObjectWriter;
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
 import org.apache.htrace.HTraceConfiguration;
@@ -23,8 +25,11 @@
 import org.apache.htrace.SpanReceiver;
 
 import java.io.BufferedWriter;
+import java.io.FileOutputStream;
 import java.io.FileWriter;
 import java.io.IOException;
+import java.io.OutputStreamWriter;
+import java.io.Writer;
 import java.util.concurrent.ExecutorService;
 import java.util.concurrent.LinkedBlockingQueue;
 import java.util.concurrent.ThreadPoolExecutor;
@@ -42,9 +47,9 @@
   public static final int CAPACITY_DEFAULT = 5000;
   // default timeout duration when calling executor.awaitTermination()
   public static final long EXECUTOR_TERMINATION_TIMEOUT_DURATION_DEFAULT = 60;
+  private static ObjectWriter JSON_WRITER = new ObjectMapper().writer();
   private String file;
-  private FileWriter fwriter;
-  private BufferedWriter bwriter;
+  private Writer writer;
   private ExecutorService executor;
   private long executorTerminationTimeoutDuration;
 
@@ -57,15 +62,28 @@
     }
     this.executor = new ThreadPoolExecutor(1, 1, 0, TimeUnit.SECONDS,
         new LinkedBlockingQueue<Runnable>(capacity));
+    boolean success = false;
+    FileOutputStream fos = null;
     try {
-      this.fwriter = new FileWriter(this.file, true);
+      fos = new FileOutputStream(file, true);
+      this.writer = new BufferedWriter(
+          new OutputStreamWriter(fos,"UTF-8"));
+      success = true;
     } catch (IOException ioe) {
       throw new RuntimeException(ioe);
+    } finally {
+      if (!success) {
+        if (fos == null) {
+          try {
+            fos.close();
+          } catch (IOException e) {
+            LOG.error("Error closing output stream for " + file, e);
+          }
+        }
+      }
     }
-    this.bwriter = new BufferedWriter(fwriter);
   }
 
-
   private class WriteSpanRunnable implements Runnable {
     public final Span span;
 
@@ -76,9 +94,8 @@
     @Override
     public void run() {
       try {
-        bwriter.write(span.toJson());
-        bwriter.newLine();
-        bwriter.flush();
+        JSON_WRITER.writeValue(writer, this);
+        writer.write("%n");
       } catch (IOException e) {
         LOG.error("Error when writing to file: " + file, e);
       }
@@ -104,14 +121,9 @@
     }
 
     try {
-      fwriter.close();
+      writer.close();
     } catch (IOException e) {
-      LOG.error("Error closing filewriter for file: " + file, e);
-    }
-    try {
-      bwriter.close();
-    } catch (IOException e) {
-      LOG.error("Error closing bufferedwriter for file: " + file, e);
+      LOG.error("Error closing writer for file: " + file, e);
     }
   }
-}
\ No newline at end of file
+}
diff --git a/htrace-core/src/main/java/org/apache/htrace/impl/MilliSpan.java b/htrace-core/src/main/java/org/apache/htrace/impl/MilliSpan.java
index 597b566..b34df64 100644
--- a/htrace-core/src/main/java/org/apache/htrace/impl/MilliSpan.java
+++ b/htrace-core/src/main/java/org/apache/htrace/impl/MilliSpan.java
@@ -30,6 +30,7 @@
 
 import java.io.IOException;
 import java.io.StringWriter;
+import java.io.UnsupportedEncodingException;
 import java.math.BigInteger;
 import java.util.ArrayList;
 import java.util.Collections;
@@ -56,7 +57,7 @@
   private final long traceId;
   private final long parents[];
   private final long spanId;
-  private Map<byte[], byte[]> traceInfo = null;
+  private Map<String, String> traceInfo = null;
   private final String processId;
   private List<TimelineAnnotation> timeline = null;
 
@@ -75,7 +76,7 @@
     private long traceId;
     private long parents[];
     private long spanId;
-    private Map<byte[], byte[]> traceInfo = null;
+    private Map<String, String> traceInfo = null;
     private String processId;
     private List<TimelineAnnotation> timeline = null;
 
@@ -121,7 +122,7 @@
       return this;
     }
 
-    public Builder traceInfo(Map<byte[], byte[]> traceInfo) {
+    public Builder traceInfo(Map<String, String> traceInfo) {
       this.traceInfo = traceInfo.isEmpty() ? null : traceInfo;
       return this;
     }
@@ -237,9 +238,19 @@
   }
 
   @Override
-  public void addKVAnnotation(byte[] key, byte[] value) {
+  public void addKVAnnotation(byte[] key, byte[] value)  {
+    // TODO: remove this method
+    try {
+      addKVAnnotation(new String(key, "UTF-8"), new String(value, "UTF-8"));
+    } catch (UnsupportedEncodingException e) {
+      throw new RuntimeException(e);
+    }
+  }
+
+  @Override
+  public void addKVAnnotation(String key, String value) {
     if (traceInfo == null)
-      traceInfo = new HashMap<byte[], byte[]>();
+      traceInfo = new HashMap<String, String>();
     traceInfo.put(key, value);
   }
 
@@ -252,7 +263,7 @@
   }
 
   @Override
-  public Map<byte[], byte[]> getKVAnnotations() {
+  public Map<String, String> getKVAnnotations() {
     if (traceInfo == null)
       return Collections.emptyMap();
     return Collections.unmodifiableMap(traceInfo);
@@ -310,12 +321,11 @@
       builder.parents(parents);
       JsonNode traceInfoNode = root.get("n");
       if (traceInfoNode != null) {
-        HashMap<byte[], byte[]> traceInfo = new HashMap<byte[], byte[]>();
+        HashMap<String, String> traceInfo = new HashMap<String, String>();
         for (Iterator<String> iter = traceInfoNode.fieldNames();
              iter.hasNext(); ) {
           String field = iter.next();
-          traceInfo.put(field.getBytes("UTF-8"),
-              traceInfoNode.get(field).asText().getBytes("UTF-8"));
+          traceInfo.put(field, traceInfoNode.get(field).asText());
         }
         builder.traceInfo(traceInfo);
       }
diff --git a/htrace-core/src/test/java/org/apache/htrace/impl/TestMilliSpan.java b/htrace-core/src/test/java/org/apache/htrace/impl/TestMilliSpan.java
index 677ec61..7ad0482 100644
--- a/htrace-core/src/test/java/org/apache/htrace/impl/TestMilliSpan.java
+++ b/htrace-core/src/test/java/org/apache/htrace/impl/TestMilliSpan.java
@@ -41,24 +41,14 @@
     assertEquals(expected.getSpanId(), got.getSpanId());
     assertEquals(expected.getProcessId(), got.getProcessId());
     assertEquals(expected.getParentId(), got.getParentId());
-    Map<byte[], byte[]> expectedT = expected.getKVAnnotations();
-    Map<byte[], byte[]> gotT = got.getKVAnnotations();
+    Map<String, String> expectedT = expected.getKVAnnotations();
+    Map<String, String> gotT = got.getKVAnnotations();
     if (expectedT == null) {
       assertEquals(null, gotT);
     } else {
       assertEquals(expectedT.size(), gotT.size());
-      Map<String, String> expectedTMap = new HashMap<String, String>();
-      for (byte[] key : expectedT.keySet()) {
-        expectedTMap.put(new String(key, "UTF-8"),
-            new String(expectedT.get(key), "UTF-8"));
-      }
-      Map<String, String> gotTMap = new HashMap<String, String>();
-      for (byte[] key : gotT.keySet()) {
-        gotTMap.put(new String(key, "UTF-8"),
-            new String(gotT.get(key), "UTF-8"));
-      }
-      for (String key : expectedTMap.keySet()) {
-        assertEquals(expectedTMap.get(key), gotTMap.get(key));
+      for (String key : expectedT.keySet()) {
+        assertEquals(expectedT.get(key), gotT.get(key));
       }
     }
     List<TimelineAnnotation> expectedTimeline =
@@ -137,9 +127,9 @@
         processId("b2408.halxg.com:8080").
         spanId(111111111L).
         traceId(4443);
-    Map<byte[], byte[]> traceInfo = new HashMap<byte[], byte[]>();
-    traceInfo.put("abc".getBytes("UTF-8"), "123".getBytes("UTF-8"));
-    traceInfo.put("def".getBytes("UTF-8"), "456".getBytes("UTF-8"));
+    Map<String, String> traceInfo = new HashMap<String, String>();
+    traceInfo.put("abc", "123");
+    traceInfo.put("def", "456");
     builder.traceInfo(traceInfo);
     List<TimelineAnnotation> timeline = new LinkedList<TimelineAnnotation>();
     timeline.add(new TimelineAnnotation(310L, "something happened"));
diff --git a/htrace-hbase/src/test/java/org/apache/htrace/impl/TestHBaseSpanReceiver.java b/htrace-hbase/src/test/java/org/apache/htrace/impl/TestHBaseSpanReceiver.java
index d3cffe2..52b344c 100644
--- a/htrace-hbase/src/test/java/org/apache/htrace/impl/TestHBaseSpanReceiver.java
+++ b/htrace-hbase/src/test/java/org/apache/htrace/impl/TestHBaseSpanReceiver.java
@@ -189,7 +189,7 @@
     }
 
     @Override
-    public Map<byte[], byte[]> getKVAnnotations() {
+    public Map<String, String> getKVAnnotations() {
       return Collections.emptyMap();
     }
 
@@ -202,6 +202,9 @@
     public void addKVAnnotation(byte[] key, byte[] value) {}
 
     @Override
+    public void addKVAnnotation(String key, String value) {}
+
+    @Override
     public void addTimelineAnnotation(String msg) {}
 
     @Override
diff --git a/htrace-zipkin/src/main/java/org/apache/htrace/zipkin/HTraceToZipkinConverter.java b/htrace-zipkin/src/main/java/org/apache/htrace/zipkin/HTraceToZipkinConverter.java
index 09ab1ea..8bd6442 100644
--- a/htrace-zipkin/src/main/java/org/apache/htrace/zipkin/HTraceToZipkinConverter.java
+++ b/htrace-zipkin/src/main/java/org/apache/htrace/zipkin/HTraceToZipkinConverter.java
@@ -23,8 +23,11 @@
 import com.twitter.zipkin.gen.Span;
 import com.twitter.zipkin.gen.zipkinCoreConstants;
 
+import org.apache.commons.logging.Log;
+import org.apache.commons.logging.LogFactory;
 import org.apache.htrace.TimelineAnnotation;
 
+import java.io.UnsupportedEncodingException;
 import java.util.ArrayList;
 import java.util.HashMap;
 import java.util.List;
@@ -72,6 +75,7 @@
  * <p/>
  */
 public class HTraceToZipkinConverter {
+  private static final Log LOG = LogFactory.getLog(HTraceToZipkinConverter.class);
 
   private final int ipv4Address;
   private final short port;
@@ -145,11 +149,15 @@
   private List<BinaryAnnotation> createZipkinBinaryAnnotations(org.apache.htrace.Span span,
                                                                Endpoint ep) {
     List<BinaryAnnotation> l = new ArrayList<BinaryAnnotation>();
-    for (Map.Entry<byte[], byte[]> e : span.getKVAnnotations().entrySet()) {
+    for (Map.Entry<String, String> e : span.getKVAnnotations().entrySet()) {
       BinaryAnnotation binaryAnn = new BinaryAnnotation();
       binaryAnn.setAnnotation_type(AnnotationType.BYTES);
-      binaryAnn.setKey(new String(e.getKey()));
-      binaryAnn.setValue(e.getValue());
+      binaryAnn.setKey(e.getKey());
+      try {
+        binaryAnn.setValue(e.getValue().getBytes("UTF-8"));
+      } catch (UnsupportedEncodingException ex) {
+        LOG.error("Error encoding string as UTF-8", ex);
+      }
       binaryAnn.setHost(ep);
       l.add(binaryAnn);
     }