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Diffstat (limited to 'gson/src/main/java/com/google/gson/JsonStreamParser.java')
-rw-r--r-- | gson/src/main/java/com/google/gson/JsonStreamParser.java | 122 |
1 files changed, 122 insertions, 0 deletions
diff --git a/gson/src/main/java/com/google/gson/JsonStreamParser.java b/gson/src/main/java/com/google/gson/JsonStreamParser.java new file mode 100644 index 00000000..f0438db3 --- /dev/null +++ b/gson/src/main/java/com/google/gson/JsonStreamParser.java @@ -0,0 +1,122 @@ +/* + * 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(); + } +} |