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rstoyanchevrstoyanchev
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Efficient ETag parsing
Closes gh-33372
1 parent 406b33d commit 582bfcc

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3 files changed

+180
-43
lines changed

3 files changed

+180
-43
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‎spring-web/src/main/java/org/springframework/http/ETag.java

+161
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,161 @@
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/*
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* Copyright 2002-2024 the original author or authors.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* https://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package org.springframework.http;
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import java.util.ArrayList;
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import java.util.List;
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import org.apache.commons.logging.Log;
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import org.apache.commons.logging.LogFactory;
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import org.springframework.util.StringUtils;
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/**
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* Represents an ETag for HTTP conditional requests.
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*
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* @author Rossen Stoyanchev
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* @since 5.3.38
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* @see <a href="https://datatracker.ietf.org/doc/html/rfc7232">RFC 7232</a>
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*/
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public class ETag {
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private static final Log logger = LogFactory.getLog(ETag.class);
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private static final ETag WILDCARD = new ETag("*", false);
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private final String tag;
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private final boolean weak;
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public ETag(String tag, boolean weak) {
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this.tag = tag;
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this.weak = weak;
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}
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public String tag() {
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return this.tag;
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}
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public boolean weak() {
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return this.weak;
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}
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/**
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* Whether this a wildcard tag matching to any entity tag value.
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*/
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public boolean isWildcard() {
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return (this == WILDCARD);
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}
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/**
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* Return the fully formatted tag including "W/" prefix and quotes.
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*/
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public String formattedTag() {
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if (this == WILDCARD) {
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return "*";
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}
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return (this.weak ? "W/" : "") + "\"" + this.tag + "\"";
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}
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@Override
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public String toString() {
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return formattedTag();
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}
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/**
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* Parse entity tags from an "If-Match" or "If-None-Match" header.
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* @param source the source string to parse
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* @return the parsed ETags
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*/
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public static List<ETag> parse(String source) {
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List<ETag> result = new ArrayList<>();
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State state = State.BEFORE_QUOTES;
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int startIndex = -1;
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boolean weak = false;
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for (int i = 0; i < source.length(); i++) {
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char c = source.charAt(i);
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if (state == State.IN_QUOTES) {
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if (c == '"') {
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String tag = source.substring(startIndex, i);
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if (StringUtils.hasText(tag)) {
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result.add(new ETag(tag, weak));
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}
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state = State.AFTER_QUOTES;
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startIndex = -1;
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weak = false;
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}
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continue;
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}
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if (Character.isWhitespace(c)) {
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continue;
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}
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if (c == ',') {
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state = State.BEFORE_QUOTES;
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continue;
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}
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if (state == State.BEFORE_QUOTES) {
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if (c == '*') {
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result.add(WILDCARD);
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state = State.AFTER_QUOTES;
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continue;
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}
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if (c == '"') {
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state = State.IN_QUOTES;
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startIndex = i + 1;
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continue;
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}
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if (c == 'W' && source.length() > i + 2) {
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if (source.charAt(i + 1) == '/' && source.charAt(i + 2) == '"') {
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state = State.IN_QUOTES;
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i = i + 2;
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startIndex = i + 1;
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weak = true;
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continue;
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}
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}
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}
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if (logger.isDebugEnabled()) {
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logger.debug("Unexpected char at index " + i);
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}
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}
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if (state != State.IN_QUOTES && logger.isDebugEnabled()) {
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logger.debug("Expected closing '\"'");
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}
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return result;
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}
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private enum State {
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BEFORE_QUOTES, IN_QUOTES, AFTER_QUOTES
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}
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}

‎spring-web/src/main/java/org/springframework/http/HttpHeaders.java

+14-30
Original file line numberDiff line numberDiff line change
@@ -40,8 +40,6 @@
4040
import java.util.Map;
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import java.util.Set;
4242
import java.util.StringJoiner;
43-
import java.util.regex.Matcher;
44-
import java.util.regex.Pattern;
4543
import java.util.stream.Collectors;
4644

4745
import org.springframework.lang.Nullable;
@@ -393,12 +391,6 @@ public class HttpHeaders implements MultiValueMap<String, String>, Serializable
393391
*/
394392
public static final HttpHeaders EMPTY = new ReadOnlyHttpHeaders(new LinkedMultiValueMap<>());
395393

396-
/**
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* Pattern matching ETag multiple field values in headers such as "If-Match", "If-None-Match".
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* @see <a href="https://tools.ietf.org/html/rfc7232#section-2.3">Section 2.3 of RFC 7232</a>
399-
*/
400-
private static final Pattern ETAG_HEADER_VALUE_PATTERN = Pattern.compile("\\*|\\s*((W\\/)?(\"[^\"]*\"))\\s*,?");
401-
402394
private static final DecimalFormatSymbols DECIMAL_FORMAT_SYMBOLS = new DecimalFormatSymbols(Locale.ENGLISH);
403395

404396
private static final ZoneId GMT = ZoneId.of("GMT");
@@ -1568,35 +1560,27 @@ public void clearContentHeaders() {
15681560

15691561
/**
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* Retrieve a combined result from the field values of the ETag header.
1571-
* @param headerName the header name
1563+
* @param name the header name
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* @return the combined result
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* @throws IllegalArgumentException if parsing fails
15741566
* @since 4.3
15751567
*/
1576-
protected List<String> getETagValuesAsList(String headerName) {
1577-
List<String> values = get(headerName);
1578-
if (values != null) {
1579-
List<String> result = new ArrayList<>();
1580-
for (String value : values) {
1581-
if (value != null) {
1582-
Matcher matcher = ETAG_HEADER_VALUE_PATTERN.matcher(value);
1583-
while (matcher.find()) {
1584-
if ("*".equals(matcher.group())) {
1585-
result.add(matcher.group());
1586-
}
1587-
else {
1588-
result.add(matcher.group(1));
1589-
}
1590-
}
1591-
if (result.isEmpty()) {
1592-
throw new IllegalArgumentException(
1593-
"Could not parse header '" + headerName + "' with value '" + value + "'");
1594-
}
1568+
protected List<String> getETagValuesAsList(String name) {
1569+
List<String> values = get(name);
1570+
if (values == null) {
1571+
return Collections.emptyList();
1572+
}
1573+
List<String> result = new ArrayList<>();
1574+
for (String value : values) {
1575+
if (value != null) {
1576+
List<ETag> tags = ETag.parse(value);
1577+
Assert.notEmpty(tags, "Could not parse header '" + name + "' with value '" + value + "'");
1578+
for (ETag tag : tags) {
1579+
result.add(tag.formattedTag());
15951580
}
15961581
}
1597-
return result;
15981582
}
1599-
return Collections.emptyList();
1583+
return result;
16001584
}
16011585

16021586
/**

‎spring-web/src/main/java/org/springframework/web/context/request/ServletWebRequest.java

+5-13
Original file line numberDiff line numberDiff line change
@@ -1,5 +1,5 @@
11
/*
2-
* Copyright 2002-2022 the original author or authors.
2+
* Copyright 2002-2024 the original author or authors.
33
*
44
* Licensed under the Apache License, Version 2.0 (the "License");
55
* you may not use this file except in compliance with the License.
@@ -26,13 +26,12 @@
2626
import java.util.Locale;
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import java.util.Map;
2828
import java.util.TimeZone;
29-
import java.util.regex.Matcher;
30-
import java.util.regex.Pattern;
3129

3230
import javax.servlet.http.HttpServletRequest;
3331
import javax.servlet.http.HttpServletResponse;
3432
import javax.servlet.http.HttpSession;
3533

34+
import org.springframework.http.ETag;
3635
import org.springframework.http.HttpHeaders;
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import org.springframework.http.HttpMethod;
3837
import org.springframework.http.HttpStatus;
@@ -54,12 +53,6 @@ public class ServletWebRequest extends ServletRequestAttributes implements Nativ
5453

5554
private static final List<String> SAFE_METHODS = Arrays.asList("GET", "HEAD");
5655

57-
/**
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* Pattern matching ETag multiple field values in headers such as "If-Match", "If-None-Match".
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* @see <a href="https://tools.ietf.org/html/rfc7232#section-2.3">Section 2.3 of RFC 7232</a>
60-
*/
61-
private static final Pattern ETAG_HEADER_VALUE_PATTERN = Pattern.compile("\\*|\\s*((W\\/)?(\"[^\"]*\"))\\s*,?");
62-
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/**
6457
* Date formats as specified in the HTTP RFC.
6558
* @see <a href="https://tools.ietf.org/html/rfc7231#section-7.1.1.1">Section 7.1.1.1 of RFC 7231</a>
@@ -289,11 +282,10 @@ private boolean validateIfNoneMatch(@Nullable String etag) {
289282
etag = etag.substring(2);
290283
}
291284
while (ifNoneMatch.hasMoreElements()) {
292-
String clientETags = ifNoneMatch.nextElement();
293-
Matcher etagMatcher = ETAG_HEADER_VALUE_PATTERN.matcher(clientETags);
294285
// Compare weak/strong ETags as per https://tools.ietf.org/html/rfc7232#section-2.3
295-
while (etagMatcher.find()) {
296-
if (StringUtils.hasLength(etagMatcher.group()) && etag.equals(etagMatcher.group(3))) {
286+
for (ETag requestedETag : ETag.parse(ifNoneMatch.nextElement())) {
287+
String tag = requestedETag.tag();
288+
if (StringUtils.hasLength(tag) && etag.equals(padEtagIfNecessary(tag))) {
297289
this.notModified = true;
298290
break;
299291
}

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