Spring Framework agent guidelines

Concise extract of CONTRIBUTING.md, which remains the reference for humans.

Build

• Gradle build, JDK from .sdkmanrc (currently JDK 25, sdk env install / sdk env); artifacts target Java 17+.
• Scope builds to the modules you touched: ./gradlew :spring-webmvc:test, a single test with --tests <fully.qualified.ClassTests>.
• Run ./gradlew :<module>:check before finishing: it runs tests and Checkstyle (src/checkstyle/checkstyle.xml), which enforces most of the code style below.
• NullAway null-safety checks run during compilation; fix reported errors instead of suppressing them.
• Do not run clean unless needed; the build is incremental and cached.
• Reference docs: ./gradlew antora, output in framework-docs/build/site/index.html.

Code style

• Match surrounding code; do not reformat unrelated code; a file should look like it was written by a single author.
• Tabs, LF, UTF-8, no trailing whitespace.
• Aim for 90 characters per line for code (105 acceptable, 120 max) and ~80 for Javadoc.
• Wrap lines after separators (, + ? : && ||), never before.
• K&R braces, with else, catch, and finally on a new line.
• Two blank lines before fields, constructors, static {} blocks, and inner classes; one blank line after a multiline method signature.
• Import order, groups separated by a blank line: java.*, then javax.* + jakarta.*, then others, then org.springframework.*, then static imports.
• No wildcard imports. No static imports in production code except constants/enum constants and third-party DSL factory methods; use them in tests (e.g. assertThat).
• Every source file: Apache 2.0 license header (Copyright 2002-present the original author or authors., copy from an existing file), package, imports, exactly one top-level class.
• Always reference fields with this., never methods. Always add @Override.
• No var in production code. No single-character variable names. Wrap ternaries in parentheses with the non-null condition first: (foo != null ? foo : "default").
• Argument checks: Assert.notNull(event, "Event must not be null"); state checks: Assert.state(...).
• Null-safety with JSpecify: packages are @NullMarked in package-info.java, use org.jspecify.annotations.Nullable explicitly (e.g. private @Nullable String name;), repeat super method nullness on overrides, @Contract where useful.
• Static utility classes: abstract, Utils suffix, private constructor.
• No System.out/System.err or printStackTrace().

Javadoc

• First sentence in imperative style ("Return", not "Returns"); <p> to start extra paragraphs; {@code} for code and null.
• No blank line between method description and tags; do not indent wrapped tag descriptions.
• Add @since to new classes and new public/protected methods; omit a .0 patch version (@since 7.1, not 7.1.0).
• Tag order for types: @author, @since, @param, @see, @deprecated; for members: @param, @return, @throws, @since, @see, @deprecated.

Tests

• Add or update tests for any code change.
• JUnit Jupiter, AssertJ (including assertThatIllegalArgumentException() and similar), Mockito. No JUnit 4/Jupiter/TestNG assertions, no Hamcrest.
• Test class names end with Tests.
• Use the standard Mockito API (when(...).thenReturn(...)), not BDDMockito (given(...)), in new test code; do not migrate existing BDDMockito usage.

Docs

• Reference docs are AsciiDoc in framework-docs/modules/ROOT; code snippets for include-code:: live in framework-docs/src/main/{java,kotlin}.

Commits and pull requests

• Pull requests target main.
• Subject: imperative, capitalized verb, at most 55 characters, no fix:/docs: prefixes, no issue/PR number, no trailing period.
• Body wrapped at 72 characters explaining the motivation, followed by Closes gh-123 (or See gh-123), then a Signed-off-by: Name <email> trailer (DCO, use git commit -s).
• Never write annotations verbatim in commit messages or PR titles (it mentions GitHub users): enclose them in backticks, as in `@Override`.
• Changes must be reviewed by a human who remains accountable for them before being submitted.