java 27 lines · 6 steps

Parsing an HTTP Cookie header in Java

Split a raw Cookie header into an ordered map of names to decoded values, defensively skipping malformed pieces.

Explained by highlit
Intermediate string-parsing http url-decoding defensive-coding
1public static Map<String, String> parseCookieHeader(String header) {
2 Map<String, String> cookies = new LinkedHashMap<>();
3 if (header == null || header.isBlank()) {
4 return cookies;
5 }
6 
7 for (String pair : header.split(";")) {
8 int eq = pair.indexOf('=');
9 if (eq < 0) {
10 continue;
11 }
12 
13 String name = pair.substring(0, eq).trim();
14 if (name.isEmpty()) {
15 continue;
16 }
17 
18 String value = pair.substring(eq + 1).trim();
19 if (value.length() >= 2 && value.startsWith("\"") && value.endsWith("\"")) {
20 value = value.substring(1, value.length() - 1);
21 }
22 
23 cookies.putIfAbsent(name, URLDecoder.decode(value, StandardCharsets.UTF_8));
24 }
25 
26 return cookies;
27}
01 / 01
STEP 01

Walkthrough

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Three takeaways
  1. 1Guard against null and empty input up front so the happy path stays clean.
  2. 2Skip malformed entries with continue instead of throwing, keeping the parser tolerant of real-world headers.
  3. 3Preserving insertion order and honoring first-wins semantics matters when duplicate cookie names appear.

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