# Boot 4.1.1: where the auto-configuration classes a starter refers to now live

--- entries in spring-boot-autoconfigure's own AutoConfiguration.imports ---
12

--- JacksonAutoConfiguration: which jar, which package ---
spring-boot-autoconfigure-4.1.1.jar, classes named JacksonAutoConfiguration: 0
spring-boot-jackson-4.1.1.jar: org/springframework/boot/jackson/autoconfigure/JacksonAutoConfiguration.class

--- what @AutoConfiguration is made of (javap -v, class-level annotations) ---
org.springframework.context.annotation.Configuration(
proxyBeanMethods=false
org.springframework.boot.autoconfigure.AutoConfigureBefore
org.springframework.boot.autoconfigure.AutoConfigureAfter

--- AutoConfigurationExcludeFilter, the filter @SpringBootApplication's scan applies: the classes it tests for (javap -c) ---
ldc #26 // class org/springframework/context/annotation/Configuration
ldc #40 // class org/springframework/boot/autoconfigure/AutoConfiguration
ldc #40 // class org/springframework/boot/autoconfigure/AutoConfiguration
invokestatic #65 // Method org/springframework/boot/context/annotation/ImportCandidates.load:(Ljava/lang/Class;Ljava/lang/ClassLoader;)Lorg/springframework/boot/context/annotation/ImportCandidates;

--- the Boot 3 import, compiled against the 4.1.1 jars ---
masker-spring-boot-autoconfigure/src/broken/OldJacksonImport.java:4: error: package org.springframework.boot.autoconfigure.jackson does not exist
import org.springframework.boot.autoconfigure.jackson.JacksonAutoConfiguration;
                                                     ^
masker-spring-boot-autoconfigure/src/broken/OldJacksonImport.java:7: error: cannot find symbol
@AutoConfiguration(after = JacksonAutoConfiguration.class)
                           ^
  symbol: class JacksonAutoConfiguration
2 errors