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README.md

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+# sdjpa4-demo
+
+Runnable companion project for [Spring Data JPA 3 to 4 Migration Guide](https://ankurm.com/spring-data-jpa-3-to-4-migration-guide-2/) on ankurm.com.
+
+Four entities, two repositories, a `@NullMarked` package, seven passing behavior tests, and an A-G demo runner that prints every labelled console output shown in the article. Boots H2 in memory, so there's nothing to install beyond a JDK.
+
+Built and verified on Eclipse Temurin JDK 21.0.11, Spring Boot 4.0.6, Spring Data JPA 4.0.6, Hibernate ORM 7.2, H2 in-memory.
+
+## Run it
+
+```
+git clone https://ankurm.com/git.app/asmhatre/sdjpa4-demo.git
+cd sdjpa4-demo
+./mvnw spring-boot:run   # prints the labelled A-G demonstrations
+./mvnw test               # runs the 7 behavior tests (all green)
+```