[SPR-13537] UriComponentsBuilder interprets empty request parameters as
null Created: 04/Oct/15 Updated: 12/Oct/15 Resolved: 12/Oct/15
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Spring Framework
Web
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Bug
Sam Brannen
Works as Designed
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relates to SPR-13524 HtmlUnitRequestBuilder doesn't handle...
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Rossen Stoyanchev
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16 weeks, 3 days ago
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Rossen Stoyanchev
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Description
Status Quo
brought it to our attention that UriComponentsBuilder returns null for empty request
parameters instead of an empty string.
For example, given a request such as http://example.com/login?error, the error request
parameter is empty but still present in the query string. Thus we would expect
UriComponentsBuilder to store its value as an empty string; however,
UriComponentsBuilder currently stores it in its query map as null.
This is contrast to Spring MVC's support for @RequestParameter. When using
@RequestParameter in a controller handler method, Spring always passes in an empty string
for an empty request parameter value, regardless of whether the = sign is present in the query
string.
Analysis
The source of this behavior is in UriComponentsBuilder.query(String), specifically in this
line:
queryParam(name, (value != null ? value :
(StringUtils.hasLength(eq) ? "" : null)));
For empty request parameter values, if the = sign is present, the value is set to an empty string
""; otherwise, the value is set to null.
Furthermore, similar logic exists in UriComponentsBuilder.queryParam(String,
Object...): queryParam(...) stores null instead of an empty string for an empty value.
Deliverables
1. Ensure that UriComponentsBuilder stores empty request parameters as empty strings.
 Updated both query(String) and queryParam(String, Object...)
 See TODO in UriComponentsBuilderTests.
Comments
Comment by Rossen Stoyanchev [ 12/Oct/15 ]
Resolving in favor of the existing behavior which preserves between empty value and value-less
query parameters. It is conceivable that servers may have slightly different semantics for that.
Note that the UriTemplateHandler introduced in 4.2 could be used to change this behavior
where usage of the RestTemplate is concerned at least.
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