java 19 lines · 5 steps

Building URIs safely with UriComponentsBuilder in Spring

How Spring's fluent builder assembles an encoded search URL from query, paging, and optional parameters.

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Spring Intermediate url-building builder-pattern encoding optional query-parameters
1public URI buildSearchUri(String query, int page, int size, List<String> tags) {
2 UriComponentsBuilder builder = UriComponentsBuilder
3 .fromUriString("https://api.example.com")
4 .path("/v2/products/search")
5 .queryParam("q", query)
6 .queryParam("page", page)
7 .queryParam("size", size)
8 .queryParam("sort", "relevance,desc");
9 
10 if (tags != null && !tags.isEmpty()) {
11 builder.queryParam("tag", tags.toArray());
12 }
13 
14 return builder
15 .queryParamIfPresent("currency", Optional.ofNullable(defaultCurrency))
16 .encode(StandardCharsets.UTF_8)
17 .build()
18 .toUri();
19}
01 / 01
STEP 01

Walkthrough

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Three takeaways
  1. 1A fluent builder lets you compose a URL declaratively instead of concatenating fragile strings.
  2. 2Encoding once at build time via encode() prevents malformed URLs from unescaped user input.
  3. 3queryParamIfPresent and Optional express conditional parameters without scattering null checks.

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