Make Expressions max length configurable (fixes #2916)#3422
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velo merged 1 commit intoJun 19, 2026
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The maximum length of a single template expression was hard-coded to 10000 characters in feign.template.Expressions, throwing IllegalArgumentException for anything longer with no way to opt out. Make the limit configurable through the "feign.template.expression.maxLength" system property (default 10000), and allow disabling the check entirely by setting it to a non-positive value. Fixes OpenFeign#2916 Signed-off-by: seonwoo_jung <79202163+seonwooj0810@users.noreply.github.com>
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The default expression length guard stays unchanged, and the new system property is additive for users who need to tune or disable it explicitly. The ExpressionsTest additions cover the default, configured, and disabled cases, and the patch does not introduce a compatibility or security concern.
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Fixes #2916
Problem
feign.template.Expressionshard-codes the maximum length of a single template expression toMAX_EXPRESSION_LENGTH = 10000. Any expression longer than that fails withIllegalArgumentException: expression is too long. Max length: 10000, with no way to raise or disable the limit. As noted in the issue, applications that legitimately need longer expressions have no escape hatch.Change
feign.template.expression.maxLengthsystem property, defaulting to10000(unchanged behavior).0(or any non-positive value) disables the length check entirely, as requested in the issue.The constant was used in a single place (
Expressions.create), so the change is self-contained and the default keeps existing behavior intact.Tests
Added
ExpressionsTestcases:tooLongExpressionFailsWithDefaultLimit— default 10000 limit still rejects over-long expressions.maxExpressionLengthIsConfigurable— a custom limit is honored (Max length: 5).lengthCheckCanBeDisabled— with the property set to0, an expression beyond the default limit is accepted.Verification done: built and ran
./mvnw -pl core -am test -Dtest=ExpressionsTest(7/7 pass) and validated formatting with the project'sgit-code-format-maven-plugin:validate-code-format. All commits are DCO signed-off.