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/*
* 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 com.google.gson.internal.Streams;
import com.google.gson.stream.JsonReader;
import com.google.gson.stream.JsonToken;
import com.google.gson.stream.MalformedJsonException;
import java.io.IOException;
import java.io.Reader;
import java.io.StringReader;
import java.util.Iterator;
import java.util.NoSuchElementException;
/**
* A streaming parser that allows reading of multiple {@link JsonElement}s from the specified reader
* asynchronously. The JSON data is parsed in lenient mode, see also
* {@link JsonReader#setLenient(boolean)}.
*
* <p>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:
*
* <pre>
* 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();
* }
* }
* </pre>
*
* @author Inderjeet Singh
* @author Joel Leitch
* @since 1.4
*/
public final class JsonStreamParser implements Iterator<JsonElement> {
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 {@link JsonElement} on the reader. Throws a
* {@link NoSuchElementException} if no element is available.
*
* @return the next available {@code JsonElement} on the reader.
* @throws JsonParseException if the incoming stream is malformed JSON.
* @throws NoSuchElementException if no {@code JsonElement} is available.
* @since 1.4
*/
@Override
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);
}
}
/**
* Returns true if a {@link JsonElement} is available on the input for consumption
* @return true if a {@link JsonElement} is available on the input, false otherwise
* @throws JsonParseException if the incoming stream is malformed JSON.
* @since 1.4
*/
@Override
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 {@link Iterator} method is not relevant for stream parsing and hence is not
* implemented.
* @since 1.4
*/
@Override
public void remove() {
throw new UnsupportedOperationException();
}
}
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