126 lines
3.8 KiB
Java
126 lines
3.8 KiB
Java
/*
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* Copyright (C) 2009 Google Inc.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package com.google.gson;
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import com.google.gson.internal.Streams;
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import com.google.gson.stream.JsonReader;
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import com.google.gson.stream.JsonToken;
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import com.google.gson.stream.MalformedJsonException;
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import java.io.IOException;
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import java.io.Reader;
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import java.io.StringReader;
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import java.util.Iterator;
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import java.util.NoSuchElementException;
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/**
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* A streaming parser that allows reading of multiple {@link JsonElement}s from the specified reader
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* asynchronously. The JSON data is parsed in lenient mode, see also
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* {@link JsonReader#setLenient(boolean)}.
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*
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* <p>This class is conditionally thread-safe (see Item 70, Effective Java second edition). To
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* properly use this class across multiple threads, you will need to add some external
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* synchronization. For example:
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*
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* <pre>
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* JsonStreamParser parser = new JsonStreamParser("['first'] {'second':10} 'third'");
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* JsonElement element;
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* synchronized (parser) { // synchronize on an object shared by threads
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* if (parser.hasNext()) {
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* element = parser.next();
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* }
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* }
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* </pre>
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*
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* @author Inderjeet Singh
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* @author Joel Leitch
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* @since 1.4
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*/
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public final class JsonStreamParser implements Iterator<JsonElement> {
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private final JsonReader parser;
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private final Object lock;
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/**
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* @param json The string containing JSON elements concatenated to each other.
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* @since 1.4
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*/
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public JsonStreamParser(String json) {
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this(new StringReader(json));
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}
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/**
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* @param reader The data stream containing JSON elements concatenated to each other.
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* @since 1.4
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*/
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public JsonStreamParser(Reader reader) {
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parser = new JsonReader(reader);
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parser.setLenient(true);
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lock = new Object();
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}
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/**
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* Returns the next available {@link JsonElement} on the reader. Throws a
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* {@link NoSuchElementException} if no element is available.
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*
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* @return the next available {@code JsonElement} on the reader.
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* @throws JsonParseException if the incoming stream is malformed JSON.
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* @throws NoSuchElementException if no {@code JsonElement} is available.
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* @since 1.4
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*/
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@Override
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public JsonElement next() throws JsonParseException {
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if (!hasNext()) {
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throw new NoSuchElementException();
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}
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try {
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return Streams.parse(parser);
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} catch (StackOverflowError e) {
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throw new JsonParseException("Failed parsing JSON source to Json", e);
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} catch (OutOfMemoryError e) {
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throw new JsonParseException("Failed parsing JSON source to Json", e);
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}
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}
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/**
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* Returns true if a {@link JsonElement} is available on the input for consumption
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* @return true if a {@link JsonElement} is available on the input, false otherwise
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* @throws JsonParseException if the incoming stream is malformed JSON.
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* @since 1.4
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*/
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@Override
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public boolean hasNext() {
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synchronized (lock) {
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try {
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return parser.peek() != JsonToken.END_DOCUMENT;
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} catch (MalformedJsonException e) {
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throw new JsonSyntaxException(e);
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} catch (IOException e) {
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throw new JsonIOException(e);
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}
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}
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}
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/**
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* This optional {@link Iterator} method is not relevant for stream parsing and hence is not
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* implemented.
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* @since 1.4
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*/
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@Override
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public void remove() {
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throw new UnsupportedOperationException();
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}
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}
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