Added methods to convert to JsonElement in TypeAdapter.

Using lenient mode while working with Gson.
Handling nulls while invoking legacy Gson type adapters.

gson/src/main/java/com/google/gson/Gson.java

@@ -28,6 +28,7 @@ import java.util.LinkedList;
 import java.util.List;
 import java.util.Map;
 
+import com.google.gson.internal.Streams;
 import com.google.gson.internal.bind.ArrayTypeAdapter;
 import com.google.gson.internal.bind.CollectionTypeAdapter;
 import com.google.gson.internal.bind.MiniGson;
@@ -264,13 +265,7 @@ public final class Gson {
   public JsonElement toJsonTree(Object src, Type typeOfSrc) {
     // Serialize 'src' to JSON, then deserialize that to a JSON tree.
     TypeAdapter adapter = miniGson.getAdapter(TypeToken.get(typeOfSrc));
-    StringWriter writer = new StringWriter();
+    return adapter.toJsonElement(src);
-    try {
-      adapter.write(writer, src);
-    } catch (IOException e) {
-      throw new RuntimeException(e);
-    }
-    return Streams.parse(new JsonReader(new StringReader(writer.toString())));
   }
 
   /**

gson/src/main/java/com/google/gson/GsonToMiniGsonTypeAdapter.java

@@ -21,6 +21,7 @@ import java.io.StringReader;
 import java.io.StringWriter;
 import java.lang.reflect.Type;
 
+import com.google.gson.internal.Streams;
 import com.google.gson.internal.bind.MiniGson;
 import com.google.gson.internal.bind.TypeAdapter;
 import com.google.gson.reflect.TypeToken;
@@ -61,6 +62,10 @@ final class GsonToMiniGsonTypeAdapter implements TypeAdapter.Factory {
           // TODO: handle if serializer is null
           throw new UnsupportedOperationException();
         }
+        if (value == null) {
+          writer.nullValue();
+          return;
+        }
         JsonElement element = serializer.serialize(value, typeOfT, createSerializationContext(miniGson));
         Streams.write(element, serializeNulls, writer);
       }
@@ -71,15 +76,8 @@ final class GsonToMiniGsonTypeAdapter implements TypeAdapter.Factory {
     return new JsonSerializationContext() {
       @Override
       JsonElement serialize(Object src, Type typeOfSrc, boolean preserveType, boolean defaultOnly) {
-        try {
         TypeToken typeToken = TypeToken.get(typeOfSrc);
-          String json = miniGson.getAdapter(typeToken).toJson(src);
+        return miniGson.getAdapter(typeToken).toJsonElement(src);
-          JsonReader jsonReader = new JsonReader(new StringReader(json));
-          jsonReader.setLenient(true);
-          return Streams.parse(jsonReader);
-        } catch (IOException e) {
-          throw new RuntimeException(e);
-        }
       }
     };
   }
@@ -87,17 +85,8 @@ final class GsonToMiniGsonTypeAdapter implements TypeAdapter.Factory {
     return new JsonDeserializationContext() {
       @Override
       public <T> T deserialize(JsonElement json, Type typeOfT) throws JsonParseException {
-        try {
         TypeToken typeToken = TypeToken.get(typeOfT);
-          StringWriter stringWriter = new StringWriter();
+        return (T) miniGson.getAdapter(typeToken).fromJsonElement(json);
-          JsonWriter jsonWriter = new JsonWriter(stringWriter);
-          jsonWriter.setLenient(true);
-          Streams.write(json, serializeNulls, jsonWriter);
-          Object target = miniGson.getAdapter(typeToken).fromJson(stringWriter.toString());
-          return (T) target;
-        } catch (IOException e) {
-          throw new JsonParseException(e);
-        }
       }
     };
   }

gson/src/main/java/com/google/gson/JsonElement.java

@@ -16,6 +16,7 @@
 
 package com.google.gson;
 
+import com.google.gson.internal.Streams;
 import com.google.gson.stream.JsonWriter;
 import java.io.IOException;
 import java.io.StringWriter;

gson/src/main/java/com/google/gson/JsonParser.java

@@ -15,6 +15,7 @@
  */
 package com.google.gson;
 
+import com.google.gson.internal.Streams;
 import com.google.gson.stream.JsonReader;
 import com.google.gson.stream.JsonToken;
 import com.google.gson.stream.MalformedJsonException;

gson/src/main/java/com/google/gson/JsonPrimitive.java

@@ -17,6 +17,8 @@
 package com.google.gson;
 
 import com.google.gson.internal.$Gson$Preconditions;
+import com.google.gson.internal.LazilyParsedNumber;
+
 import java.math.BigDecimal;
 import java.math.BigInteger;
 

gson/src/main/java/com/google/gson/JsonStreamParser.java

@@ -22,6 +22,7 @@ import java.io.StringReader;
 import java.util.Iterator;
 import java.util.NoSuchElementException;
 
+import com.google.gson.internal.Streams;
 import com.google.gson.stream.JsonReader;
 import com.google.gson.stream.JsonToken;
 import com.google.gson.stream.MalformedJsonException;

gson/src/main/java/com/google/gson/internal/LazilyParsedNumber.java

@@ -13,7 +13,7 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-package com.google.gson;
+package com.google.gson.internal;
 
 import java.math.BigInteger;
 
@@ -23,10 +23,10 @@ import java.math.BigInteger;
  * @author Inderjeet Singh
  */
 @SuppressWarnings("serial")
-final class LazilyParsedNumber extends Number {
+public final class LazilyParsedNumber extends Number {
   private final String value;
 
-  LazilyParsedNumber(String value) {
+  public LazilyParsedNumber(String value) {
     this.value = value;
   }
 

gson/src/main/java/com/google/gson/internal/Streams.java

@@ -14,8 +14,16 @@
  * limitations under the License.
  */
 
-package com.google.gson;
+package com.google.gson.internal;
 
+import com.google.gson.JsonArray;
+import com.google.gson.JsonElement;
+import com.google.gson.JsonIOException;
+import com.google.gson.JsonNull;
+import com.google.gson.JsonObject;
+import com.google.gson.JsonParseException;
+import com.google.gson.JsonPrimitive;
+import com.google.gson.JsonSyntaxException;
 import com.google.gson.stream.JsonReader;
 import com.google.gson.stream.JsonWriter;
 import com.google.gson.stream.MalformedJsonException;
@@ -27,12 +35,12 @@ import java.util.Map;
 /**
  * Reads and writes GSON parse trees over streams.
  */
-final class Streams {
+public final class Streams {
 
   /**
    * Takes a reader in any state and returns the next value as a JsonElement.
    */
-  static JsonElement parse(JsonReader reader) throws JsonParseException {
+  public static JsonElement parse(JsonReader reader) throws JsonParseException {
     boolean isEmpty = true;
     try {
       reader.peek();
@@ -96,7 +104,7 @@ final class Streams {
   /**
    * Writes the JSON element to the writer, recursively.
    */
-  static void write(JsonElement element, boolean serializeNulls, JsonWriter writer)
+  public static void write(JsonElement element, boolean serializeNulls, JsonWriter writer)
       throws IOException {
     if (element == null || element.isJsonNull()) {
       if (serializeNulls) {
@@ -142,7 +150,7 @@ final class Streams {
     }
   }
 
-  static Writer writerForAppendable(Appendable appendable) {
+  public static Writer writerForAppendable(Appendable appendable) {
     return appendable instanceof Writer ? (Writer) appendable : new AppendableWriter(appendable);
   }
 

gson/src/main/java/com/google/gson/internal/bind/TypeAdapter.java

@@ -16,15 +16,18 @@
 
 package com.google.gson.internal.bind;
 
-import com.google.gson.reflect.TypeToken;
-import com.google.gson.stream.JsonReader;
-import com.google.gson.stream.JsonWriter;
 import java.io.IOException;
 import java.io.Reader;
 import java.io.StringReader;
 import java.io.StringWriter;
 import java.io.Writer;
 
+import com.google.gson.JsonElement;
+import com.google.gson.internal.Streams;
+import com.google.gson.reflect.TypeToken;
+import com.google.gson.stream.JsonReader;
+import com.google.gson.stream.JsonWriter;
+
 public abstract class TypeAdapter<T> {
   public abstract T read(JsonReader reader) throws IOException;
   public abstract void write(JsonWriter writer, T value) throws IOException;
@@ -50,6 +53,34 @@ public abstract class TypeAdapter<T> {
     return read(reader);
   }
 
+  public JsonElement toJsonElement(T src) {
+    try {
+      StringWriter stringWriter = new StringWriter();
+      JsonWriter jsonWriter = new JsonWriter(stringWriter);
+      jsonWriter.setLenient(true);
+      write(jsonWriter, src);
+      JsonReader reader = new JsonReader(new StringReader(stringWriter.toString()));
+      reader.setLenient(true);
+      return Streams.parse(reader);
+    } catch (IOException e) {
+      throw new RuntimeException(e);
+    }
+  }
+
+  public T fromJsonElement(JsonElement json) {
+    try {
+      StringWriter stringWriter = new StringWriter();
+      JsonWriter jsonWriter = new JsonWriter(stringWriter);
+      jsonWriter.setLenient(true);
+      Streams.write(json, false, jsonWriter);
+      JsonReader jsonReader = new JsonReader(new StringReader(stringWriter.toString()));
+      jsonReader.setLenient(true);
+      return read(jsonReader);
+    } catch (IOException e) {
+      throw new RuntimeException(e);
+    }
+  }
+
   public interface Factory {
     <T> TypeAdapter<T> create(MiniGson context, TypeToken<T> type);
   }

gson/src/test/java/com/google/gson/JsonParserTest.java

@@ -17,6 +17,7 @@
 package com.google.gson;
 
 import com.google.gson.common.TestTypes.BagOfPrimitives;
+import com.google.gson.internal.Streams;
 import com.google.gson.stream.JsonReader;
 import java.io.CharArrayReader;
 import java.io.CharArrayWriter;