spring StringDecoder 源码
spring StringDecoder 代码
文件路径：/spring-core/src/main/java/org/springframework/core/codec/StringDecoder.java
/*
* Copyright 2002-2022 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
*
* https://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.Collection;
import java.util.Collections;
import java.util.List;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;
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.LimitedDataBufferList;
import org.springframework.core.io.buffer.PooledDataBuffer;
import org.springframework.core.log.LogFormatUtils;
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, either splitting
* or aggregating incoming data chunks to realign along newlines delimiters
* and produce a stream of strings. This is useful for streaming but is also
* necessary to ensure that that multibyte characters can be decoded correctly,
* avoiding split-character issues. The default delimiters used by default are
* {@code \n} and {@code \r\n} but that can be customized.
*
* @author Sebastien Deleuze
* @author Brian Clozel
* @author Arjen Poutsma
* @author Mark Paluch
* @since 5.0
* @see CharSequenceEncoder
*/
public final class StringDecoder extends AbstractDataBufferDecoder<String> {
/** 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 \r\n} and {@code \n}. */
public static final List<String> DEFAULT_DELIMITERS = List.of("\r\n", "\n");
private final List<String> delimiters;
private final boolean stripDelimiter;
private Charset defaultCharset = DEFAULT_CHARSET;
private final ConcurrentMap<Charset, byte[][]> delimitersCache = new ConcurrentHashMap<>();
private StringDecoder(List<String> delimiters, boolean stripDelimiter, MimeType... mimeTypes) {
super(mimeTypes);
Assert.notEmpty(delimiters, "'delimiters' must not be empty");
this.delimiters = new ArrayList<>(delimiters);
this.stripDelimiter = stripDelimiter;
}
/**
* Set the default character set to fall back on if the MimeType does not specify any.
* <p>By default this is {@code UTF-8}.
* @param defaultCharset the charset to fall back on
* @since 5.2.9
*/
public void setDefaultCharset(Charset defaultCharset) {
this.defaultCharset = defaultCharset;
}
/**
* Return the configured {@link #setDefaultCharset(Charset) defaultCharset}.
* @since 5.2.9
*/
public Charset getDefaultCharset() {
return this.defaultCharset;
}
@Override
public boolean canDecode(ResolvableType elementType, @Nullable MimeType mimeType) {
return (elementType.resolve() == String.class && super.canDecode(elementType, mimeType));
}
@Override
public Flux<String> decode(Publisher<DataBuffer> input, ResolvableType elementType,
@Nullable MimeType mimeType, @Nullable Map<String, Object> hints) {
byte[][] delimiterBytes = getDelimiterBytes(mimeType);
LimitedDataBufferList chunks = new LimitedDataBufferList(getMaxInMemorySize());
DataBufferUtils.Matcher matcher = DataBufferUtils.matcher(delimiterBytes);
return Flux.from(input)
.concatMapIterable(buffer -> processDataBuffer(buffer, matcher, chunks))
.concatWith(Mono.defer(() -> {
if (chunks.isEmpty()) {
return Mono.empty();
}
DataBuffer lastBuffer = chunks.get(0).factory().join(chunks);
chunks.clear();
return Mono.just(lastBuffer);
}))
.doOnTerminate(chunks::releaseAndClear)
.doOnDiscard(PooledDataBuffer.class, PooledDataBuffer::release)
.map(buffer -> decode(buffer, elementType, mimeType, hints));
}
private byte[][] getDelimiterBytes(@Nullable MimeType mimeType) {
return this.delimitersCache.computeIfAbsent(getCharset(mimeType), charset -> {
byte[][] result = new byte[this.delimiters.size()][];
for (int i = 0; i < this.delimiters.size(); i++) {
result[i] = this.delimiters.get(i).getBytes(charset);
}
return result;
});
}
private Collection<DataBuffer> processDataBuffer(
DataBuffer buffer, DataBufferUtils.Matcher matcher, LimitedDataBufferList chunks) {
try {
List<DataBuffer> result = null;
do {
int endIndex = matcher.match(buffer);
if (endIndex == -1) {
chunks.add(buffer);
DataBufferUtils.retain(buffer); // retain after add (may raise DataBufferLimitException)
break;
}
int startIndex = buffer.readPosition();
int length = (endIndex - startIndex + 1);
DataBuffer slice = buffer.retainedSlice(startIndex, length);
result = (result != null ? result : new ArrayList<>());
if (chunks.isEmpty()) {
if (this.stripDelimiter) {
slice.writePosition(slice.writePosition() - matcher.delimiter().length);
}
result.add(slice);
}
else {
chunks.add(slice);
DataBuffer joined = buffer.factory().join(chunks);
if (this.stripDelimiter) {
joined.writePosition(joined.writePosition() - matcher.delimiter().length);
}
result.add(joined);
chunks.clear();
}
buffer.readPosition(endIndex + 1);
}
while (buffer.readableByteCount() > 0);
return (result != null ? result : Collections.emptyList());
}
finally {
DataBufferUtils.release(buffer);
}
}
@Override
public String decode(DataBuffer dataBuffer, ResolvableType elementType,
@Nullable MimeType mimeType, @Nullable Map<String, Object> hints) {
Charset charset = getCharset(mimeType);
CharBuffer charBuffer = charset.decode(dataBuffer.asByteBuffer());
DataBufferUtils.release(dataBuffer);
String value = charBuffer.toString();
LogFormatUtils.traceDebug(logger, traceOn -> {
String formatted = LogFormatUtils.formatValue(value, !traceOn);
return Hints.getLogPrefix(hints) + "Decoded " + formatted;
});
return value;
}
private Charset getCharset(@Nullable MimeType mimeType) {
if (mimeType != null && mimeType.getCharset() != null) {
return mimeType.getCharset();
}
else {
return getDefaultCharset();
}
}
/**
* 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"}.
* @param delimiters delimiter strings to use to split the input stream
* @param stripDelimiter whether to remove delimiters from the resulting
* input strings
*/
public static StringDecoder textPlainOnly(List<String> delimiters, boolean stripDelimiter) {
return new StringDecoder(delimiters, stripDelimiter, new MimeType("text", "plain", DEFAULT_CHARSET));
}
/**
* 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.
* @param delimiters delimiter strings to use to split the input stream
* @param stripDelimiter whether to remove delimiters from the resulting
* input strings
*/
public static StringDecoder allMimeTypes(List<String> delimiters, boolean stripDelimiter) {
return new StringDecoder(delimiters, stripDelimiter,
new MimeType("text", "plain", DEFAULT_CHARSET), MimeTypeUtils.ALL);
}
}
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