| /* |
| * Copyright (C) 2010 The Android Open Source Project |
| * |
| * 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.android.json.stream; |
| |
| import java.io.IOException; |
| import java.io.Writer; |
| |
| /** |
| * Writes a JSON (<a href="http://www.ietf.org/rfc/rfc4627.txt">RFC 4627</a>) encoded value to a |
| * stream, one token at a time. The stream includes both literal values (strings, numbers, booleans |
| * and nulls) as well as the begin and end delimiters of objects and arrays. |
| * |
| * <h3>Encoding JSON</h3> |
| * |
| * To encode your data as JSON, create a new {@code JsonWriter}. Each JSON document must contain one |
| * top-level array or object. Call methods on the writer as you walk the structure's contents, |
| * nesting arrays and objects as necessary: |
| * |
| * <ul> |
| * <li>To write <strong>arrays</strong>, first call {@link #beginArray()}. Write each of the |
| * array's elements with the appropriate {@link #value} methods or by nesting other arrays and |
| * objects. Finally close the array using {@link #endArray()}. |
| * <li>To write <strong>objects</strong>, first call {@link #beginObject()}. Write each of the |
| * object's properties by alternating calls to {@link #name} with the property's value. Write |
| * property values with the appropriate {@link #value} method or by nesting other objects or |
| * arrays. Finally close the object using {@link #endObject()}. |
| * </ul> |
| * |
| * <h3>Example</h3> |
| * |
| * Suppose we'd like to encode a stream of messages such as the following: |
| * |
| * <pre>{@code |
| * [ |
| * { |
| * "id": 912345678901, |
| * "text": "How do I write JSON on Android?", |
| * "geo": null, |
| * "user": { |
| * "name": "android_newb", |
| * "followers_count": 41 |
| * } |
| * }, |
| * { |
| * "id": 912345678902, |
| * "text": "@android_newb just use android.util.JsonWriter!", |
| * "geo": [50.454722, -104.606667], |
| * "user": { |
| * "name": "jesse", |
| * "followers_count": 2 |
| * } |
| * } |
| * ] |
| * }</pre> |
| * |
| * This code encodes the above structure: |
| * |
| * <pre>{@code |
| * public void writeJsonStream(OutputStream out, List<Message> messages) throws IOException { |
| * JsonWriter writer = new JsonWriter(new OutputStreamWriter(out, "UTF-8")); |
| * writer.setIndent(" "); |
| * writeMessagesArray(writer, messages); |
| * writer.close(); |
| * } |
| * |
| * public void writeMessagesArray(JsonWriter writer, List<Message> messages) throws IOException { |
| * writer.beginArray(); |
| * for (Message message : messages) { |
| * writeMessage(writer, message); |
| * } |
| * writer.endArray(); |
| * } |
| * |
| * public void writeMessage(JsonWriter writer, Message message) throws IOException { |
| * writer.beginObject(); |
| * writer.name("id").value(message.getId()); |
| * writer.name("text").value(message.getText()); |
| * if (message.getGeo() != null) { |
| * writer.name("geo"); |
| * writeDoublesArray(writer, message.getGeo()); |
| * } else { |
| * writer.name("geo").nullValue(); |
| * } |
| * writer.name("user"); |
| * writeUser(writer, message.getUser()); |
| * writer.endObject(); |
| * } |
| * |
| * public void writeUser(JsonWriter writer, User user) throws IOException { |
| * writer.beginObject(); |
| * writer.name("name").value(user.getName()); |
| * writer.name("followers_count").value(user.getFollowersCount()); |
| * writer.endObject(); |
| * } |
| * |
| * public void writeDoublesArray(JsonWriter writer, List<Double> doubles) throws IOException { |
| * writer.beginArray(); |
| * for (Double value : doubles) { |
| * writer.value(value); |
| * } |
| * writer.endArray(); |
| * } |
| * }</pre> |
| * |
| * <p>Each {@code JsonWriter} may be used to write a single JSON stream. Instances of this class are |
| * not thread safe. Calls that would result in a malformed JSON string will fail with an {@link |
| * IllegalStateException}. |
| */ |
| public class NewlineDelimitedJsonWriter extends JsonWriter { |
| private static final String NEW_LINE = "\n"; |
| /** |
| * Creates a new instance that writes a JSON-encoded stream to {@code out}. For best |
| * performance, ensure {@link Writer} is buffered; wrapping in {@link java.io.BufferedWriter |
| * BufferedWriter} if necessary. |
| */ |
| public NewlineDelimitedJsonWriter(Writer out) { |
| super(out); |
| } |
| |
| /** |
| * Sets the indentation string is no opt for newline-delimited JSON |
| * |
| * @param indent a string containing only whitespace. |
| */ |
| @Override |
| public void setIndent(String indent) { |
| // no opt on Indent |
| super.setIndent(null); |
| } |
| |
| /** Sets newline-delimited for a JSON object. */ |
| public void newlineDelimited() throws IOException { |
| mOut.write(NEW_LINE); |
| } |
| |
| /** |
| * Flushes and closes this writer and the underlying {@link Writer}. |
| * |
| * @throws IOException if the JSON document is incomplete. |
| */ |
| public void close() throws IOException { |
| mOut.close(); |
| } |
| |
| /** |
| * Inserts any necessary separators and whitespace before a literal value, inline array, or |
| * inline object. Also adjusts the stack to expect either a closing bracket or another element. |
| * |
| * @param root true if the value is a new array or object, the two values permitted as top-level |
| * elements. |
| */ |
| @Override |
| protected void beforeValue(boolean root) throws IOException { |
| switch (peek()) { |
| case EMPTY_DOCUMENT: // first in document |
| if (!root) { |
| throw new IllegalStateException("JSON must start with an array or an object."); |
| } |
| break; |
| |
| case EMPTY_ARRAY: // first in array |
| replaceTop(JsonScope.NONEMPTY_ARRAY); |
| newline(); |
| break; |
| |
| case NONEMPTY_ARRAY: // another in array |
| mOut.append(','); |
| newline(); |
| break; |
| |
| case DANGLING_NAME: // value for name |
| mOut.append(mSeparator); |
| replaceTop(JsonScope.NONEMPTY_OBJECT); |
| break; |
| |
| default: |
| throw new IllegalStateException("Nesting problem: " + mStack); |
| } |
| } |
| } |