The JacksonCodec implementation of toString/toBuffer lacks of efficie…

…ncy compared to the DatabindCodec implementation which uses the buffer recyler of Jackson.

Update the JacksonCodec implementation to use the buffer recycler instead.

src/main/java/io/vertx/core/json/jackson/JacksonCodec.java

@@ -12,6 +12,7 @@
 package io.vertx.core.json.jackson;
 
 import com.fasterxml.jackson.core.*;
+import com.fasterxml.jackson.core.io.SegmentedStringWriter;
 import com.fasterxml.jackson.core.type.TypeReference;
 import io.netty.buffer.ByteBuf;
 import io.netty.buffer.ByteBufInputStream;
@@ -108,35 +109,33 @@ public <T> T fromValue(Object json, TypeReference<T> type) {
 
   @Override
   public String toString(Object object, boolean pretty) throws EncodeException {
-    StringWriter sw = new StringWriter();
-    JsonGenerator generator = createGenerator(sw, pretty);
-    try {
+    com.fasterxml.jackson.core.util.BufferRecycler br = factory._getBufferRecycler();
+    try (SegmentedStringWriter sw = new SegmentedStringWriter(br)) {
+      com.fasterxml.jackson.core.JsonGenerator generator = createGenerator(sw, pretty);
       encodeJson(object, generator);
-      generator.flush();
-      return sw.toString();
-    } catch (IOException e) {
-      throw new EncodeException(e.getMessage(), e);
+      generator.close();
+      return sw.getAndClear();
+    } catch (java.io.IOException e) {
+      throw new io.vertx.core.json.EncodeException(e.getMessage(), e);
     } finally {
-      close(generator);
+      br.releaseToPool();
     }
   }
 
   @Override
   public Buffer toBuffer(Object object, boolean pretty) throws EncodeException {
-    ByteBuf buf = Unpooled.buffer();
-    // There is no need to use a try with resources here as jackson
-    // is a well-behaved and always calls the closes all streams in the
-    // "finally" block bellow.
-    ByteBufOutputStream out = new ByteBufOutputStream(buf);
-    JsonGenerator generator = createGenerator(out, pretty);
-    try {
+    com.fasterxml.jackson.core.util.BufferRecycler br = factory._getBufferRecycler();
+    try (com.fasterxml.jackson.core.util.ByteArrayBuilder bb = new com.fasterxml.jackson.core.util.ByteArrayBuilder(br)) {
+      com.fasterxml.jackson.core.JsonGenerator generator = createGenerator(bb, pretty);
       encodeJson(object, generator);
-      generator.flush();
-      return Buffer.buffer(buf);
-    } catch (IOException e) {
-      throw new EncodeException(e.getMessage(), e);
+      generator.close();
+      byte[] result = bb.toByteArray();
+      bb.release();
+      return io.vertx.core.buffer.Buffer.buffer(result);
+    } catch (java.io.IOException e) {
+      throw new io.vertx.core.json.EncodeException(e.getMessage(), e);
     } finally {
-      close(generator);
+      br.releaseToPool();
     }
   }
 
@@ -286,7 +285,7 @@ static void close(Closeable parser) {
   }
 
   // In recursive calls, the callee is in charge of opening and closing the data structure
-  private static void encodeJson(Object json, JsonGenerator generator) throws EncodeException {
+  public static void encodeJson(Object json, JsonGenerator generator) throws EncodeException {
     try {
       if (json instanceof JsonObject) {
         json = ((JsonObject)json).getMap();