org.springframework.core.codec.StringDecoder Maven / Gradle / Ivy
/*
* Copyright 2002-2018 the original author or authors.
*
* 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 org.springframework.core.codec;
import java.nio.CharBuffer;
import java.nio.charset.Charset;
import java.nio.charset.StandardCharsets;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.Map;
import java.util.stream.Collectors;
import org.reactivestreams.Publisher;
import reactor.core.publisher.Flux;
import reactor.core.publisher.Mono;
import org.springframework.core.ResolvableType;
import org.springframework.core.io.buffer.DataBuffer;
import org.springframework.core.io.buffer.DataBufferUtils;
import org.springframework.core.io.buffer.DefaultDataBufferFactory;
import org.springframework.lang.Nullable;
import org.springframework.util.Assert;
import org.springframework.util.MimeType;
import org.springframework.util.MimeTypeUtils;
/**
* Decode from a data buffer stream to a {@code String} stream. Before decoding, this decoder
* realigns the incoming data buffers so that each buffer ends with a newline.
* This is to make sure that multibyte characters are decoded properly, and do not cross buffer
* boundaries. The default delimiters ({@code \n}, {@code \r\n})can be customized.
*
* Partially inspired by Netty's {@code DelimiterBasedFrameDecoder}.
*
* @author Sebastien Deleuze
* @author Brian Clozel
* @author Arjen Poutsma
* @author Mark Paluch
* @since 5.0
* @see CharSequenceEncoder
*/
public class StringDecoder extends AbstractDataBufferDecoder {
private static final DataBuffer END_FRAME = new DefaultDataBufferFactory().wrap(new byte[0]);
/**
* The default charset to use, i.e. "UTF-8".
*/
public static final Charset DEFAULT_CHARSET = StandardCharsets.UTF_8;
/**
* The default delimiter strings to use, i.e. {@code \n} and {@code \r\n}.
*/
public static final List DEFAULT_DELIMITERS = Arrays.asList("\r\n", "\n");
private final List delimiters;
private final boolean stripDelimiter;
private StringDecoder(List delimiters, boolean stripDelimiter, MimeType... mimeTypes) {
super(mimeTypes);
Assert.notEmpty(delimiters, "'delimiters' must not be empty");
this.delimiters = new ArrayList<>(delimiters);
this.stripDelimiter = stripDelimiter;
}
@Override
public boolean canDecode(ResolvableType elementType, @Nullable MimeType mimeType) {
return (super.canDecode(elementType, mimeType) &&
String.class.equals(elementType.getRawClass()));
}
@Override
public Flux decode(Publisher inputStream, ResolvableType elementType,
@Nullable MimeType mimeType, @Nullable Map hints) {
List delimiterBytes = getDelimiterBytes(mimeType);
Flux inputFlux = Flux.from(inputStream)
.flatMap(dataBuffer -> splitOnDelimiter(dataBuffer, delimiterBytes))
.bufferUntil(StringDecoder::isEndFrame)
.flatMap(StringDecoder::joinUntilEndFrame);
return super.decode(inputFlux, elementType, mimeType, hints);
}
private List getDelimiterBytes(@Nullable MimeType mimeType) {
Charset charset = getCharset(mimeType);
return this.delimiters.stream()
.map(s -> s.getBytes(charset))
.collect(Collectors.toList());
}
/**
* Splits the given data buffer on delimiter boundaries. The returned Flux contains a
* {@link #END_FRAME} buffer after each delimiter.
*/
private Flux splitOnDelimiter(DataBuffer dataBuffer, List delimiterBytes) {
List frames = new ArrayList<>();
do {
int length = Integer.MAX_VALUE;
byte[] matchingDelimiter = null;
for (byte[] delimiter : delimiterBytes) {
int idx = indexOf(dataBuffer, delimiter);
if (idx >= 0 && idx < length) {
length = idx;
matchingDelimiter = delimiter;
}
}
DataBuffer frame;
int readPosition = dataBuffer.readPosition();
if (matchingDelimiter != null) {
if (this.stripDelimiter) {
frame = dataBuffer.slice(readPosition, length);
}
else {
frame = dataBuffer.slice(readPosition, length + matchingDelimiter.length);
}
dataBuffer.readPosition(readPosition + length + matchingDelimiter.length);
frames.add(DataBufferUtils.retain(frame));
frames.add(END_FRAME);
}
else {
frame = dataBuffer.slice(readPosition, dataBuffer.readableByteCount());
dataBuffer.readPosition(readPosition + dataBuffer.readableByteCount());
frames.add(DataBufferUtils.retain(frame));
}
}
while (dataBuffer.readableByteCount() > 0);
DataBufferUtils.release(dataBuffer);
return Flux.fromIterable(frames);
}
/**
* Finds the given delimiter in the given data buffer. Return the index of the delimiter, or
* -1 if not found.
*/
private static int indexOf(DataBuffer dataBuffer, byte[] delimiter) {
for (int i = dataBuffer.readPosition(); i < dataBuffer.writePosition(); i++) {
int dataBufferPos = i;
int delimiterPos = 0;
while (delimiterPos < delimiter.length) {
if (dataBuffer.getByte(dataBufferPos) != delimiter[delimiterPos]) {
break;
}
else {
dataBufferPos++;
if (dataBufferPos == dataBuffer.writePosition() &&
delimiterPos != delimiter.length - 1) {
return -1;
}
}
delimiterPos++;
}
if (delimiterPos == delimiter.length) {
return i - dataBuffer.readPosition();
}
}
return -1;
}
/**
* Checks whether the given buffer is {@link #END_FRAME}.
*/
private static boolean isEndFrame(DataBuffer dataBuffer) {
return dataBuffer == END_FRAME;
}
/**
* Joins the given list of buffers into a single buffer.
*/
private static Mono joinUntilEndFrame(List dataBuffers) {
if (!dataBuffers.isEmpty()) {
int lastIdx = dataBuffers.size() - 1;
if (isEndFrame(dataBuffers.get(lastIdx))) {
dataBuffers.remove(lastIdx);
}
}
Flux flux = Flux.fromIterable(dataBuffers);
return DataBufferUtils.join(flux);
}
@Override
protected String decodeDataBuffer(DataBuffer dataBuffer, ResolvableType elementType,
@Nullable MimeType mimeType, @Nullable Map hints) {
Charset charset = getCharset(mimeType);
CharBuffer charBuffer = charset.decode(dataBuffer.asByteBuffer());
DataBufferUtils.release(dataBuffer);
return charBuffer.toString();
}
private static Charset getCharset(@Nullable MimeType mimeType) {
if (mimeType != null && mimeType.getCharset() != null) {
return mimeType.getCharset();
}
else {
return DEFAULT_CHARSET;
}
}
/**
* Create a {@code StringDecoder} for {@code "text/plain"}.
* @param ignored ignored
* @deprecated as of Spring 5.0.4, in favor of {@link #textPlainOnly()} or
* {@link #textPlainOnly(List, boolean)}.
*/
@Deprecated
public static StringDecoder textPlainOnly(boolean ignored) {
return textPlainOnly();
}
/**
* Create a {@code StringDecoder} for {@code "text/plain"}.
*/
public static StringDecoder textPlainOnly() {
return textPlainOnly(DEFAULT_DELIMITERS, true);
}
/**
* Create a {@code StringDecoder} for {@code "text/plain"}.
*/
public static StringDecoder textPlainOnly(List delimiters, boolean stripDelimiter) {
return new StringDecoder(delimiters, stripDelimiter,
new MimeType("text", "plain", DEFAULT_CHARSET));
}
/**
* Create a {@code StringDecoder} that supports all MIME types.
* @param ignored ignored
* @deprecated as of Spring 5.0.4, in favor of {@link #allMimeTypes()} or
* {@link #allMimeTypes(List, boolean)}.
*/
@Deprecated
public static StringDecoder allMimeTypes(boolean ignored) {
return allMimeTypes();
}
/**
* Create a {@code StringDecoder} that supports all MIME types.
*/
public static StringDecoder allMimeTypes() {
return allMimeTypes(DEFAULT_DELIMITERS, true);
}
/**
* Create a {@code StringDecoder} that supports all MIME types.
*/
public static StringDecoder allMimeTypes(List delimiters, boolean stripDelimiter) {
return new StringDecoder(delimiters, stripDelimiter,
new MimeType("text", "plain", DEFAULT_CHARSET), MimeTypeUtils.ALL);
}
}