JSpecify and Spring Null-safety

Null-safety turns hidden runtime failures into visible compile-time guarantees

Spring Framework 7.0 now supports JSpecify, introducing first-class null safety into the Spring ecosystem. This means Spring can understand nullability contracts and help you detect potential NullPointerException issues at compile time, not in production.

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What Is Null-safety?

Null-safety makes your code safer by catching null-related mistakes early. It creates clear expectations:

• What can be null

• What cannot be null

• What APIs require strict checks

This leads to fewer runtime surprises and more reliable applications.

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What Is JSpecify?

JSpecify defines standard annotations such as:

• @NonNull

• @Nullable

• @NullMarked

Spring 7 understands these annotations and applies null-safety rules consistently across your beans and application logic.

📘 JSpecify guide: https://jspecify.dev/docs/user-guide/
📘 Spring null-safety docs: https://docs.spring.io/spring-framework/reference/core/null-safety.html

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How to Enable Null-safety Checks (Maven)

To validate null-safety automatically, we use NullAway, Uber’s fast, compile-time checker, together with Error Prone:

<plugin>
    <groupId>org.apache.maven.plugins</groupId>
    <artifactId>maven-compiler-plugin</artifactId>
    <version>3.11.0</version>
    <configuration>
        <source>17</source>
        <target>8</target>
        <encoding>UTF-8</encoding>
        <compilerArgs>
            <arg>-XDcompilePolicy=simple</arg>
            <arg>--should-stop=ifError=FLOW</arg>
            <arg>-Xplugin:ErrorProne
                -XepOpt:NullAway:AnnotatedPackages=com.bomfim
                -Xep:NullAway:ERROR
                -XepExcludedPaths:.*/src/test/java/.*
            </arg>
        </compilerArgs>
        <annotationProcessorPaths>
            <path>
                <groupId>com.google.errorprone</groupId>
                <artifactId>error_prone_core</artifactId>
                <version>2.42.0</version>
            </path>
            <path>
                <groupId>com.uber.nullaway</groupId>
                <artifactId>nullaway</artifactId>
                <version>0.12.12</version>
            </path>
        </annotationProcessorPaths>
    </configuration>
</plugin>

What this setup gives you

• Compile-time null-safety enforcement

• Clear errors when annotations are violated

• Automatic protection against accidental null values

More details:
📘 NullAway JSpecify Support: https://github.com/uber/NullAway/wiki/JSpecify-Support

You can access the code here: https://github.com/ThiagoBfim/spring-news

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Using Gradle?

This talk explains it perfectly:
🎥 Null Safety in Java with JSpecify and NullAway — Sébastien Deleuze (Spring I/O 2025)

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Conclusion

With Spring 7 + JSpecify + NullAway, Java finally gets a practical, lightweight approach to null-safety. You get earlier warnings, clearer APIs, and fewer runtime surprises, all with minimal setup.

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