java.lang.NoSuchMethodError: ResponseEntity.getStatusCode() when running code built with Spring 5.x on Spring 6.x

[derkoe]

Affects: 6.0.x - tested with 6.0.4

---

The signature of ResponseEntity#getStatusCode was changed in Spring Framework 6.x - it now returns HttpStatusCode (Spring 5.x returned HttpStatus) - see #28214. The idea was that the change is backward compatible.

How to reproduce:

1. Create this simple test class in a file Test.java:

   // Test.java
   import org.springframework.http.ResponseEntity;
   
   public class Test {
     public static void main(String[] args) {
       ResponseEntity<Object> ok = ResponseEntity.ok().build();
       if (ok.getStatusCode().is2xxSuccessful()) {
         System.out.println("OK");
       }
     }
   }

2. Compile the application with Spring 5.3.x:

   javac -cp $HOME/.m2/repository/org/springframework/spring-web/5.3.24/spring-web-5.3.24.jar Test.java
   

3. Run the application with Spring 6.0x:

    java -cp "$HOME/.m2/repository/org/springframework/spring-web/6.0.4/spring-web-6.0.4.jar:$HOME/.m2/repository/org/springframework/spring-core/6.0.4/spring-core-6.0.4.jar:." Test
    Exception in thread "main" java.lang.NoSuchMethodError: 'org.springframework.http.HttpStatus org.springframework.http.ResponseEntity.getStatusCode()'
        at Test.main(Test.java:6)
   

   With Spring 5.3.x it works as expected:

    java -cp "$HOME/.m2/repository/org/springframework/spring-web/5.3.24/spring-web-5.3.24.jar:$HOME/.m2/repository/org/springframework/spring-core/5.3.24/spring-core-5.3.24.jar:." Test
   OK
   

[bclozel]

This change was done in a source compatible way, but not binary compatible way.
We don't guarantee binary compatibility between major versions, you should recompile the application with Spring Framework 6.0 on the classpath.

[derkoe]

@bclozel the issue is here that you cannot create a library that is Spring 5.x and 6.x compatible. Is this really intended?

[derkoe]

This incompatibility also exists in the other direction - code compile with 6.0.x is not running with 5.3.x

$ javac -cp $HOME/.m2/repository/org/springframework/spring-web/6.0.4/spring-web-6.0.4.jar Test.java
$ java -cp "$HOME/.m2/repository/org/springframework/spring-web/5.3.24/spring-web-5.3.24.jar:$HOME/.m2/repository/org/springframework/spring-core/5.3.24/spring-core-5.3.24.jar:." Test
Exception in thread "main" java.lang.NoSuchMethodError: 'org.springframework.http.HttpStatusCode org.springframework.http.ResponseEntity.getStatusCode()'
        at Test.main(Test.java:6)

[bclozel]

@derkoe we do our best to retain compatibility, but keeping binary compatibility between major versions is a huge ask.
I'm sorry for the inconvenience, but in this case we think the tradeoff is worth it.

You cannot create a library that is Spring 5.x and 6.x compatible in the first place anyway: they have different Java baselines. If you're compiling your library with Java 17, it's not compatible with all Spring 5.x applications.