/* * 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.io.IOException;/** * A simple implementation of the {@link JsonElementVisitor} that simply delegates the method * invocation onto a {@code delegate} instance of the {@link JsonElementVisitor}.  This object * can be used to build a chain of visitors such that each Visitor instance can perform some * operation on the {@link JsonElement} and then pass on the input to the delegate.  This kind * of pattern is sometimes referred as a "Chain of Responsibility". * * <p>The following is an example use case: * * <pre> * class JsonEscapingVisitor extends DelegatingJsonElementVisitor { *   public JsonEscapingVisitor(JsonElementVisitor) { *     super(visitor); *   } * *   public void visitPrimitive(JsonPrimitive primitive) { *     JsonPrimitive escapedPrimitive = escapePrimitiveObject(primitive); *     super.visitPrimitive(escapedPrimitive); *   } * } * * JsonElementVisitor visitor = new JsonEscapingVisitor(new FormattingVisitor()); * </pre></p> * * @author Joel Leitch */class DelegatingJsonElementVisitor implements JsonElementVisitor {  private final JsonElementVisitor delegate;  protected DelegatingJsonElementVisitor(JsonElementVisitor delegate) {    Preconditions.checkNotNull(delegate);    this.delegate = delegate;  }  public void endArray(JsonArray array) throws IOException {    delegate.endArray(array);  }  public void endObject(JsonObject object) throws IOException {    delegate.endObject(object);  }  public void startArray(JsonArray array) throws IOException {    delegate.startArray(array);  }  public void startObject(JsonObject object) throws IOException {    delegate.startObject(object);  }  public void visitArrayMember(JsonArray parent, JsonPrimitive member,       boolean isFirst) throws IOException {    delegate.visitArrayMember(parent, member, isFirst);  }  public void visitArrayMember(JsonArray parent, JsonArray member,       boolean isFirst) throws IOException {    delegate.visitArrayMember(parent, member, isFirst);  }  public void visitArrayMember(JsonArray parent, JsonObject member,       boolean isFirst) throws IOException {    delegate.visitArrayMember(parent, member, isFirst);  }  public void visitObjectMember(JsonObject parent, String memberName, JsonPrimitive member,       boolean isFirst) throws IOException {    delegate.visitObjectMember(parent, memberName, member, isFirst);  }  public void visitObjectMember(JsonObject parent, String memberName, JsonArray member,       boolean isFirst) throws IOException {    delegate.visitObjectMember(parent, memberName, member, isFirst);  }  public void visitObjectMember(JsonObject parent, String memberName, JsonObject member,       boolean isFirst) throws IOException {    delegate.visitObjectMember(parent, memberName, member, isFirst);  }  public void visitNullObjectMember(JsonObject parent, String memberName,       boolean isFirst) throws IOException {    delegate.visitNullObjectMember(parent, memberName, isFirst);  }  public void visitPrimitive(JsonPrimitive primitive) throws IOException {    delegate.visitPrimitive(primitive);  }  public void visitNull() throws IOException {    delegate.visitNull();  }  public void visitNullArrayMember(JsonArray parent, boolean isFirst) throws IOException {    delegate.visitNullArrayMember(parent, isFirst);  }}