/* * Copyright (C) 2008 Google Inc. * * 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 com.google.gson;import java.lang.reflect.Array;import java.lang.reflect.Field;import java.lang.reflect.Type;/** * A visitor that adds JSON elements corresponding to each field of an object * * @author Inderjeet Singh * @author Joel Leitch */final class JsonSerializationVisitor implements ObjectNavigator.Visitor {  private final ObjectNavigatorFactory factory;  private final ParameterizedTypeHandlerMap<JsonSerializer<?>> serializers;  private final boolean serializeNulls;  private final JsonSerializationContext context;  private JsonElement root;  JsonSerializationVisitor(ObjectNavigatorFactory factory, boolean serializeNulls,      ParameterizedTypeHandlerMap<JsonSerializer<?>> serializers,      JsonSerializationContext context) {    this.factory = factory;    this.serializeNulls = serializeNulls;    this.serializers = serializers;    this.context = context;  }    public Object getTarget() {    return null;  }  public void startVisitingObject(Object node) {    assignToRoot(new JsonObject());  }  public void visitArray(Object array, Type arrayType) {    assignToRoot(new JsonArray());    int length = Array.getLength(array);    TypeInfoArray fieldTypeInfo = TypeInfoFactory.getTypeInfoForArray(arrayType);    Type componentType = fieldTypeInfo.getSecondLevelType();    for (int i = 0; i < length; ++i) {      Object child = Array.get(array, i);      addAsArrayElement(componentType, child);    }  }  public void visitArrayField(Field f, Type typeOfF, Object obj) {    if (isFieldNull(f, obj)) {      if (serializeNulls) {        addChildAsElement(f, JsonNull.createJsonNull());      }    } else {      Object array = getFieldValue(f, obj);      addAsChildOfObject(f, typeOfF, array);    }  }  public void visitObjectField(Field f, Type typeOfF, Object obj) {    if (isFieldNull(f, obj)) {      if (serializeNulls) {        addChildAsElement(f, JsonNull.createJsonNull());      }    } else {      Object fieldValue = getFieldValue(f, obj);      // This takes care of situations where the field was declared as an Object, but the      // actual value contains something more specific. See Issue 54.      if (fieldValue != null && typeOfF == Object.class) {        typeOfF = fieldValue.getClass();      }      addAsChildOfObject(f, typeOfF, fieldValue);    }  }  private void addAsChildOfObject(Field f, Type fieldType, Object fieldValue) {    JsonElement childElement = getJsonElementForChild(fieldType, fieldValue);    addChildAsElement(f, childElement);  }  private void addChildAsElement(Field f, JsonElement childElement) {    FieldNamingStrategy namingPolicy = factory.getFieldNamingPolicy();    root.getAsJsonObject().add(namingPolicy.translateName(f), childElement);  }  private void addAsArrayElement(Type elementType, Object elementValue) {    if (elementValue == null) {      root.getAsJsonArray().add(JsonNull.createJsonNull());    } else {      JsonElement childElement = getJsonElementForChild(elementType, elementValue);      root.getAsJsonArray().add(childElement);    }  }  private JsonElement getJsonElementForChild(Type fieldType, Object fieldValue) {    ObjectNavigator on = factory.create(fieldValue, fieldType);    JsonSerializationVisitor childVisitor =        new JsonSerializationVisitor(factory, serializeNulls, serializers, context);    on.accept(childVisitor);    return childVisitor.getJsonElement();  }  @SuppressWarnings("unchecked")  public boolean visitUsingCustomHandler(Object obj, Type objType) {    JsonSerializer serializer = serializers.getHandlerFor(objType);    if (serializer != null) {      if (obj == null) {        assignToRoot(JsonNull.createJsonNull());      } else {        assignToRoot(serializer.serialize(obj, objType, context));      }      return true;    }    return false;  }  @SuppressWarnings("unchecked")  public boolean visitFieldUsingCustomHandler(Field f, Type actualTypeOfField, Object parent) {    try {      Preconditions.checkState(root.isJsonObject());      Object obj = f.get(parent);      if (obj == null) {        if (serializeNulls) {          addChildAsElement(f, JsonNull.createJsonNull());        }        return true;      }      JsonSerializer serializer = serializers.getHandlerFor(actualTypeOfField);      if (serializer != null) {        JsonElement child = serializer.serialize(obj, actualTypeOfField, context);        addChildAsElement(f, child);        return true;      }      return false;    } catch (IllegalAccessException e) {      throw new RuntimeException();    }  }  private void assignToRoot(JsonElement newRoot) {    Preconditions.checkNotNull(newRoot);    root = newRoot;  }  private boolean isFieldNull(Field f, Object obj) {    return getFieldValue(f, obj) == null;  }  private Object getFieldValue(Field f, Object obj) {    try {      return f.get(obj);    } catch (IllegalAccessException e) {      throw new RuntimeException(e);    }  }  public JsonElement getJsonElement() {    return root;  }}