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Explore the source code of the class JsonStreamParser.java

/*
 * Copyright (C) 2009 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.EOFException;
import java.io.IOException;
import java.io.Reader;
import java.io.StringReader;
import java.util.Iterator;
import java.util.NoSuchElementException;

import com.google.gson.internal.Streams;
import com.google.gson.stream.JsonReader;
import com.google.gson.stream.JsonToken;
import com.google.gson.stream.MalformedJsonException;

/**
 * A streaming parser that allows reading of multiple [email protected] JsonElement}s from the specified reader
 * asynchronously.
 * 
 * 

This class is conditionally thread-safe (see Item 70, Effective Java second edition). To * properly use this class across multiple threads, you will need to add some external * synchronization. For example: * *

 * JsonStreamParser parser = new JsonStreamParser("['first'] {'second':10} 'third'");
 * JsonElement element;
 * synchronized (parser) {  // synchronize on an object shared by threads
 *   if (parser.hasNext()) {
 *     element = parser.next();
 *   }
 * }
 * 
* * @author Inderjeet Singh * @author Joel Leitch * @since 1.4 */ public final class JsonStreamParser implements Iterator { private final JsonReader parser; private final Object lock; /** * @param json The string containing JSON elements concatenated to each other. * @since 1.4 */ public JsonStreamParser(String json) { this(new StringReader(json)); } /** * @param reader The data stream containing JSON elements concatenated to each other. * @since 1.4 */ public JsonStreamParser(Reader reader) { parser = new JsonReader(reader); parser.setLenient(true); lock = new Object(); } /** * Returns the next available [email protected] JsonElement} on the reader. Null if none available. * * @return the next available [email protected] JsonElement} on the reader. Null if none available. * @throws JsonParseException if the incoming stream is malformed JSON. * @since 1.4 */ public JsonElement next() throws JsonParseException { if (!hasNext()) { throw new NoSuchElementException(); } try { return Streams.parse(parser); } catch (StackOverflowError e) { throw new JsonParseException("Failed parsing JSON source to Json", e); } catch (OutOfMemoryError e) { throw new JsonParseException("Failed parsing JSON source to Json", e); } catch (JsonParseException e) { throw e.getCause() instanceof EOFException ? new NoSuchElementException() : e; } } /** * Returns true if a [email protected] JsonElement} is available on the input for consumption * @return true if a [email protected] JsonElement} is available on the input, false otherwise * @since 1.4 */ public boolean hasNext() { synchronized (lock) { try { return parser.peek() != JsonToken.END_DOCUMENT; } catch (MalformedJsonException e) { throw new JsonSyntaxException(e); } catch (IOException e) { throw new JsonIOException(e); } } } /** * This optional [email protected] Iterator} method is not relevant for stream parsing and hence is not * implemented. * @since 1.4 */ public void remove() { throw new UnsupportedOperationException(); } }