/*
* 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 {@link JsonElement}s from the specified reader
* asynchronously.
*
* <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. Null if none available.
*
* @return the next available {@link 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 {@link JsonElement} is available on the input for consumption
* @return true if a {@link 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 {@link Iterator} method is not relevant for stream parsing and hence is not
* implemented.
* @since 1.4
*/
public void
remove() {
throw new
UnsupportedOperationException();
}
}