/*
* Copyright 2014 The Netty Project
*
* The Netty Project licenses this file to you 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 io.netty.handler.codec.json;
import io.netty.buffer.ByteBuf;
import io.netty.buffer.ByteBufUtil;
import io.netty.channel.ChannelHandlerContext;
import io.netty.handler.codec.ByteToMessageDecoder;
import io.netty.channel.ChannelHandler;
import io.netty.handler.codec.CorruptedFrameException;
import io.netty.handler.codec.TooLongFrameException;
import io.netty.channel.ChannelPipeline;
import java.util.List;
/**
* Splits a byte stream of JSON objects and arrays into individual objects/arrays and passes them up the
* {@link ChannelPipeline}.
*
* This class does not do any real parsing or validation. A sequence of bytes is considered a JSON object/array
* if it contains a matching number of opening and closing braces/brackets. It's up to a subsequent
* {@link ChannelHandler} to parse the JSON text into a more usable form i.e. a POJO.
*/
public class JsonObjectDecoder extends ByteToMessageDecoder {
private static final int ST_CORRUPTED = -1;
private static final int ST_INIT = 0;
private static final int ST_DECODING_NORMAL = 1;
private static final int ST_DECODING_ARRAY_STREAM = 2;
private int openBraces;
private int idx;
private int lastReaderIndex;
private int state;
private boolean insideString;
private final int maxObjectLength;
private final boolean streamArrayElements;
public JsonObjectDecoder() {
// 1 MB
this(1024 * 1024);
}
public JsonObjectDecoder(int maxObjectLength) {
this(maxObjectLength, false);
}
public JsonObjectDecoder(boolean streamArrayElements) {
this(1024 * 1024, streamArrayElements);
}
/**
* @param maxObjectLength maximum number of bytes a JSON object/array may use (including braces and all).
* Objects exceeding this length are dropped and an {@link TooLongFrameException}
* is thrown.
* @param streamArrayElements if set to true and the "top level" JSON object is an array, each of its entries
* is passed through the pipeline individually and immediately after it was fully
* received, allowing for arrays with "infinitely" many elements.
*
*/
public JsonObjectDecoder(int maxObjectLength, boolean streamArrayElements) {
if (maxObjectLength < 1) {
throw new IllegalArgumentException("maxObjectLength must be a positive int");
}
this.maxObjectLength = maxObjectLength;
this.streamArrayElements = streamArrayElements;
}
@Override
protected void decode(ChannelHandlerContext ctx, ByteBuf in, List<Object> out) throws Exception {
if (state == ST_CORRUPTED) {
in.skipBytes(in.readableBytes());
return;
}
if (this.idx > in.readerIndex() && lastReaderIndex != in.readerIndex()) {
this.idx = in.readerIndex();
reset();
}
// index of next byte to process.
int idx = this.idx;
int wrtIdx = in.writerIndex();
if (wrtIdx > maxObjectLength) {
// buffer size exceeded maxObjectLength; discarding the complete buffer.
in.skipBytes(in.readableBytes());
reset();
throw new TooLongFrameException(
"object length exceeds " + maxObjectLength + ": " + wrtIdx + " bytes discarded");
}
for (/* use current idx */; idx < wrtIdx; idx++) {
byte c = in.getByte(idx);
if (state == ST_DECODING_NORMAL) {
decodeByte(c, in, idx);
// All opening braces/brackets have been closed. That's enough to conclude
// that the JSON object/array is complete.
if (openBraces == 0) {
ByteBuf json = extractObject(ctx, in, in.readerIndex(), idx + 1 - in.readerIndex());
if (json != null) {
out.add(json);
}
// The JSON object/array was extracted => discard the bytes from
// the input buffer.
in.readerIndex(idx + 1);
// Reset the object state to get ready for the next JSON object/text
// coming along the byte stream.
reset();
}
} else if (state == ST_DECODING_ARRAY_STREAM) {
decodeByte(c, in, idx);
if (!insideString && (openBraces == 1 && c == ',' || openBraces == 0 && c == ']')) {
// skip leading spaces. No range check is needed and the loop will terminate
// because the byte at position idx is not a whitespace.
for (int i = in.readerIndex(); Character.isWhitespace(in.getByte(i)); i++) {
in.skipBytes(1);
}
// skip trailing spaces.
int idxNoSpaces = idx - 1;
while (idxNoSpaces >= in.readerIndex() && Character.isWhitespace(in.getByte(idxNoSpaces))) {
idxNoSpaces--;
}
ByteBuf json = extractObject(ctx, in, in.readerIndex(), idxNoSpaces + 1 - in.readerIndex());
if (json != null) {
out.add(json);
}
in.readerIndex(idx + 1);
if (c == ']') {
reset();
}
}
// JSON object/array detected. Accumulate bytes until all braces/brackets are closed.
} else if (c == '{' || c == '[') {
initDecoding(c);
if (state == ST_DECODING_ARRAY_STREAM) {
// Discard the array bracket
in.skipBytes(1);
}
// Discard leading spaces in front of a JSON object/array.
} else if (Character.isWhitespace(c)) {
in.skipBytes(1);
} else {
state = ST_CORRUPTED;
throw new CorruptedFrameException(
"invalid JSON received at byte position " + idx + ": " + ByteBufUtil.hexDump(in));
}
}
if (in.readableBytes() == 0) {
this.idx = 0;
} else {
this.idx = idx;
}
this.lastReaderIndex = in.readerIndex();
}
/**
* Override this method if you want to filter the json objects/arrays that get passed through the pipeline.
*/
@SuppressWarnings("UnusedParameters")
protected ByteBuf extractObject(ChannelHandlerContext ctx, ByteBuf buffer, int index, int length) {
return buffer.retainedSlice(index, length);
}
private void decodeByte(byte c, ByteBuf in, int idx) {
if ((c == '{' || c == '[') && !insideString) {
openBraces++;
} else if ((c == '}' || c == ']') && !insideString) {
openBraces--;
} else if (c == '"') {
// start of a new JSON string. It's necessary to detect strings as they may
// also contain braces/brackets and that could lead to incorrect results.
if (!insideString) {
insideString = true;
} else {
int backslashCount = 0;
idx--;
while (idx >= 0) {
if (in.getByte(idx) == '\\') {
backslashCount++;
idx--;
} else {
break;
}
}
// The double quote isn't escaped only if there are even "\"s.
if (backslashCount % 2 == 0) {
// Since the double quote isn't escaped then this is the end of a string.
insideString = false;
}
}
}
}
private void initDecoding(byte openingBrace) {
openBraces = 1;
if (openingBrace == '[' && streamArrayElements) {
state = ST_DECODING_ARRAY_STREAM;
} else {
state = ST_DECODING_NORMAL;
}
}
private void reset() {
insideString = false;
state = ST_INIT;
openBraces = 0;
}
}