java 41 lines · 7 steps

A case-insensitive HTTP headers map in Java

Storing HTTP headers in a case-insensitive TreeMap of value lists gives clean multi-value accessors and safe reads.

Explained by highlit
Intermediate case-insensitivity multimap immutability builder-pattern null-safety
1public final class HttpHeaders {
2 
3 private final NavigableMap<String, List<String>> values =
4 new TreeMap<>(String.CASE_INSENSITIVE_ORDER);
5 
6 public HttpHeaders add(String name, String value) {
7 values.computeIfAbsent(name, k -> new ArrayList<>()).add(value);
8 return this;
9 }
10 
11 public HttpHeaders set(String name, String value) {
12 List<String> list = new ArrayList<>(1);
13 list.add(value);
14 values.put(name, list);
15 return this;
16 }
17 
18 public Optional<String> first(String name) {
19 List<String> list = values.get(name);
20 return (list == null || list.isEmpty())
21 ? Optional.empty()
22 : Optional.of(list.get(0));
23 }
24 
25 public List<String> all(String name) {
26 List<String> list = values.get(name);
27 return list == null ? List.of() : Collections.unmodifiableList(list);
28 }
29 
30 public boolean contains(String name) {
31 return values.containsKey(name);
32 }
33 
34 public List<String> remove(String name) {
35 return values.remove(name);
36 }
37 
38 public Set<String> names() {
39 return Collections.unmodifiableSet(values.keySet());
40 }
41}
01 / 01
STEP 01

Walkthrough

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Three takeaways
  1. 1A TreeMap seeded with CASE_INSENSITIVE_ORDER makes lookups match headers regardless of letter casing.
  2. 2Returning this from mutators enables a fluent chained-call API.
  3. 3Wrapping reads in Optional and unmodifiable collections shields callers from nulls and accidental mutation.

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