gson polymorhic marshaling and field naming strategy support

gson/pom.xml

@@ -7,7 +7,7 @@
     <groupId>org.immutables</groupId>
     <version>2.0-SNAPSHOT</version>
   </parent>
-  <artifactId>gson</artifactId>
+  <artifactId>immutables-gson</artifactId>
 
   <name>${project.groupId}.${project.artifactId}</name>
   <description>Gson integration for Immutables. Also includes optional integration with Jackson to speed-up
@@ -45,6 +45,13 @@
       <version>2.5.0</version>
       <optional>true</optional>
     </dependency>
+    <dependency>
+      <!-- Jackson binding have utility used when using polymorhic marshaling with jackson-core implementation -->
+      <groupId>com.fasterxml.jackson.core</groupId>
+      <artifactId>jackson-databind</artifactId>
+      <version>2.5.0</version>
+      <optional>true</optional>
+    </dependency>
     <dependency>
       <!-- Message body reader and writer provider implementation, optional dependency on JAX-RS -->
       <groupId>javax.ws.rs</groupId>

gson/src/org/immutables/gson/Gson.java

@@ -1,42 +1,107 @@
+/*
+    Copyright 2015 Immutables Authors and Contributors
+
+   Licensed under the Apache License, Version 2.0 (the "License");
+   you may not use this file except in compliance with the License.
+   You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.
+ */
 package org.immutables.gson;
 
+import java.util.Map;
+import com.google.gson.FieldNamingPolicy;
+import com.google.gson.FieldNamingStrategy;
 import com.google.gson.GsonBuilder;
 import com.google.gson.annotations.SerializedName;
 import java.lang.annotation.Documented;
 import java.lang.annotation.ElementType;
 import java.lang.annotation.Retention;
 import java.lang.annotation.RetentionPolicy;
 import java.lang.annotation.Target;
+import org.immutables.gson.adapter.ExpectedSubtypesAdapter;
+import org.immutables.gson.adapter.FieldNamingTranslator;
 
+/**
+ * The Interface Gson.
+ */
 @Retention(RetentionPolicy.SOURCE)
 public @interface Gson {
   /**
-   * Use on a top level class to generate type adapted factory.
+   * Use on a top level class to generate type adapted factory supporting directly annotated and all
+   * nested immutable types.
    * <p>
-   * Type adapter factories are also registered statically as services
-   * {@code META-INF/services/com.google.gson.TypeAdapterFactory}. Easy way to configure
-   * {@link com.google.gson.Gson}.
+   * Type adapter factories are registered statically as services
+   * {@code META-INF/services/com.google.gson.TypeAdapterFactory}. The most easy way to register all
+   * such factories {@link com.google.gson.Gson}.
    * <p>
-   * Certain are gson options are supported for immutable objects in deliberate fashion:
+   * Certain Gson options are supported for immutable objects in deliberate fashion:
    * <ul>
    * <li>{@link GsonBuilder#serializeNulls()} - When enabled, {@code null} fields and empty array
    * fields will be included, otherwise omited</li>
+   * <li>{@link GsonBuilder#setFieldNamingStrategy(FieldNamingStrategy)} - Naming strategy could be
+   * used if {@code @TypeAdapters(fieldNamingStrategy=true)}. See {@link #fieldNamingStrategy()} for
+   * more information.</li>
    * </ul>
    */
   @Documented
   @Retention(RetentionPolicy.SOURCE)
   @Target({ElementType.TYPE})
-  public @interface TypeAdapted {}
+  public @interface TypeAdapters {
+    /**
+     * When {@code namingStrategy=true}, somewhat more involved code is generated to apply naming
+     * strategies extracted from configured {@link com.google.gson.Gson} instance.
+     * <p>
+     * <em>This functionality uses runtime support class and requires that this Gson integration module
+     * jar will be available at runtime. Uses some Gson internals which could
+     * potentially break in later versions of Gson library. Uses oracle JVM internals.
+     * If you really want to discuss this functionality to be more portable,
+     * file a request at {@linkplain "https://github.com/immutables/immutables/issues"}.
+     * </em>
+     * @see FieldNamingStrategy
+     * @see FieldNamingPolicy
+     * @see GsonBuilder#setFieldNamingPolicy(FieldNamingPolicy)
+     * @see FieldNamingTranslator
+     * @return {@code true} if enabled, by default is {@code false}
+     */
+    boolean fieldNamingStrategy() default false;
+
+    /**
+     * When {@code emptyAsNulls=true}, empty arrays and objects will be omitted from output as
+     * if they where {@code null}, both field name and value will be omited.
+     * <p>
+     * Note that {@code null} skipping behaviour is controlled by
+     * {@link GsonBuilder#serializeNulls()}, which forces all nulls and empty arrays/objects to be
+     * serialized.
+     * @return {@code true} if enabled, by default is {@code false}
+     */
+    boolean emptyAsNulls() default false;
+  }
 
   /**
-   * Expected subclasses for marshaling could be specified on attribute level or an abstract
-   * supertype directly, however the former declaration site has precedence.
+   * Expected subtypes for serialization could be specified on attribute level or an abstract
+   * supertype directly, however the former declaration site has precedence. It enables polymorphic
+   * marshaling by structure. Subtype that matches JSON value will be returned, for the details
+   * please see {@link ExpectedSubtypesAdapter}.
+   * <p>
+   * Note: when this annotation is used with {@link Map} attribute, it refers to types of values,
+   * not keys.
+   * <p>
+   * <em>This functionality uses runtime support class and requires that this Gson integration module
+   * jar will be available at runtime.</em>
+   * @see ExpectedSubtypesAdapter
    * @see #value()
    * @see Named
    */
   @Retention(RetentionPolicy.SOURCE)
   @Target({ElementType.METHOD, ElementType.TYPE})
-  public @interface Subtypes {
+  public @interface ExpectedSubtypes {
 
     /**
      * Specifies expected subclasses of an abstract type that is matched during parsing by

gson/src/org/immutables/gson/stream/GsonMessageBodyProvider.java

@@ -15,14 +15,6 @@
  */
 package org.immutables.gson.stream;
 
-import org.immutables.value.Value.Style.ImplementationVisibility;
-import java.lang.reflect.Field;
-import org.immutables.value.Value;
-import java.util.List;
-import javax.ws.rs.core.Response;
-import com.google.common.base.Throwables;
-import javax.ws.rs.Consumes;
-import javax.ws.rs.Produces;
 import com.fasterxml.jackson.core.JsonFactory;
 import com.fasterxml.jackson.core.JsonGenerator;
 import com.fasterxml.jackson.core.JsonParser;
@@ -39,20 +31,26 @@
 import java.io.OutputStream;
 import java.io.OutputStreamWriter;
 import java.lang.annotation.Annotation;
+import java.lang.reflect.Field;
 import java.lang.reflect.Type;
-import java.util.Arrays;
 import java.util.Collections;
 import java.util.HashSet;
+import java.util.List;
 import java.util.ServiceLoader;
 import java.util.Set;
 import javax.annotation.Nullable;
+import javax.ws.rs.Consumes;
+import javax.ws.rs.Produces;
 import javax.ws.rs.WebApplicationException;
 import javax.ws.rs.core.MediaType;
 import javax.ws.rs.core.MultivaluedMap;
+import javax.ws.rs.core.Response;
 import javax.ws.rs.ext.MessageBodyReader;
 import javax.ws.rs.ext.MessageBodyWriter;
 import javax.ws.rs.ext.Provider;
 import org.immutables.metainf.Metainf;
+import org.immutables.value.Value;
+import org.immutables.value.Value.Style.ImplementationVisibility;
 
 /**
  * Gson serialization provider for JAX-RS 1.0 and JAX-RS 2.0.

gson/src/org/immutables/gson/stream/JsonGeneratorWriter.java

@@ -15,20 +15,20 @@
  */
 package org.immutables.gson.stream;
 
-import javax.annotation.concurrent.NotThreadSafe;
 import com.fasterxml.jackson.core.JsonGenerator;
 import com.google.gson.stream.JsonWriter;
 import java.io.IOException;
 import java.io.Writer;
+import java.util.concurrent.Callable;
+import javax.annotation.concurrent.NotThreadSafe;
 
 /**
  * {@link JsonWriter} impementation backed by Jackson's {@link JsonGenerator}.
  * Provides measurable JSON writing improvements over Gson's native implementation.
  * Error reporting is might differ, however.
  */
 @NotThreadSafe
-public class JsonGeneratorWriter extends JsonWriter {
-
+public class JsonGeneratorWriter extends JsonWriter implements Callable<JsonGenerator> {
   private static final Writer UNSUPPORTED_WRITER = new Writer() {
     @Override
     public void write(char[] cbuf, int off, int len) throws IOException {
@@ -53,6 +53,10 @@ public JsonGeneratorWriter(JsonGenerator generator) {
     this.generator = generator;
   }
 
+  public JsonGenerator getGenerator() {
+    return generator;
+  }
+
   @Override
   public JsonWriter beginArray() throws IOException {
     generator.writeStartArray();
@@ -145,4 +149,14 @@ public void close() throws IOException {
   public String toString() {
     return getClass().getSimpleName();
   }
+
+  /**
+   * Implements {@link Callable} mostly as a marker interface.
+   * Better use {@link #getGenerator()} to get generator.
+   * @return unwrapped {@link JsonGenerator}
+   */
+  @Override
+  public JsonGenerator call() throws Exception {
+    return generator;
+  }
 }

gson/src/org/immutables/gson/stream/JsonParserReader.java

@@ -15,6 +15,7 @@
  */
 package org.immutables.gson.stream;
 
+import java.util.concurrent.Callable;
 import com.fasterxml.jackson.core.JsonParser;
 import com.google.gson.stream.JsonReader;
 import com.google.gson.stream.JsonToken;
@@ -27,10 +28,10 @@
 /**
  * {@link JsonReader} impementation backed by Jackson's {@link JsonParser}.
  * Provides measurable JSON parsing improvements over Gson's native implementation.
- * Error reporting is might differ, however.
+ * Error reporting might differ, however.
  */
 @NotThreadSafe
-public class JsonParserReader extends JsonReader {
+public class JsonParserReader extends JsonReader implements Callable<JsonParser> {
 
   private static final Reader UNSUPPORTED_READER = new Reader() {
     @Override
@@ -51,6 +52,10 @@ public JsonParserReader(JsonParser parser) {
     this.parser = parser;
   }
 
+  public JsonParser getParser() {
+    return parser;
+  }
+
   @Nullable
   private com.fasterxml.jackson.core.JsonToken peek;
 
@@ -130,6 +135,7 @@ public String nextString() throws IOException {
     clearPeek();
     return value;
   }
+
   @Override
   public boolean nextBoolean() throws IOException {
     requirePeek();
@@ -216,7 +222,17 @@ private static JsonToken toGsonToken(com.fasterxml.jackson.core.JsonToken token)
     case VALUE_STRING:
       return JsonToken.STRING;
     default: // Not semantically equivalent
-      return JsonToken.END_DOCUMENT;
+      return JsonToken.NULL;
     }
   }
+
+  /**
+   * Implements {@link Callable} mostly as a marker interface.
+   * Better use {@link #getParser()} to get parser.
+   * @return unwrapped {@link JsonParser}
+   */
+  @Override
+  public JsonParser call() throws Exception {
+    return parser;
+  }
 }

gson/test/org/immutables/gson/adapters/Adapt.java → gson/test/org/immutables/gson/adapter/Adapt.java

@@ -1,4 +1,4 @@
-package org.immutables.gson.adapters;
+package org.immutables.gson.adapter;
 
 import com.google.common.collect.Multiset;
 import com.google.common.collect.SetMultimap;
@@ -11,7 +11,7 @@
 
 @Value.Immutable(builder = false)
 @Value.Nested
-@Gson.TypeAdapted
+@Gson.TypeAdapters
 public interface Adapt {
 
   @Value.Parameter

gson/test/org/immutables/gson/adapters/AdaptReadWriteTest.java → gson/test/org/immutables/gson/adapter/AdaptReadWriteTest.java

@@ -1,4 +1,4 @@
-package org.immutables.gson.adapters;
+package org.immutables.gson.adapter;
 
 import com.google.common.collect.ImmutableList;
 import com.google.gson.Gson;

gson/test/org/immutables/gson/adapters/OtherType.java → gson/test/org/immutables/gson/adapter/OtherType.java

@@ -1,4 +1,4 @@
-package org.immutables.gson.adapters;
+package org.immutables.gson.adapter;
 
 import com.google.common.collect.ListMultimap;
 import com.google.common.collect.Multiset;
@@ -11,7 +11,7 @@
 
 @Value.Immutable(builder = false)
 @Value.Nested
-@Gson.TypeAdapted
+@Gson.TypeAdapters
 public interface OtherType {
 
   @Value.Parameter