AOT Processing Fails with NoClassDefFoundError for Apache HttpClient 4.x Classes

[mingchiuli]

AOT Processing Fails with NoClassDefFoundError for Apache HttpClient 4.x Classes

Environment

• Spring Boot: 4.0.0
• Spring Data Elasticsearch: (version bundled with Spring Boot 4.0.0)
• Java: 25.0.1
• Build Tool: Gradle

Description

When upgrading to Spring Boot 4.0.0 and running AOT processing (processAot task), the build fails with NoClassDefFoundError for Apache HttpClient 4.x classes.

Stack Trace

Exception in thread "main" java.lang.NoClassDefFoundError: org/apache/http/impl/auth/BasicScheme
	at org.springframework.data.elasticsearch.client.elc.aot.ElasticsearchClientRuntimeHints.registerHints(ElasticsearchClientRuntimeHints.java:46)
	at org.springframework.context.aot.RuntimeHintsBeanFactoryInitializationAotProcessor$RuntimeHintsRegistrarContribution.lambda$applyTo$0(RuntimeHintsBeanFactoryInitializationAotProcessor.java:117)
	at java.base/java.util.LinkedHashMap$LinkedValues.forEach(LinkedHashMap.java:834)
	at org.springframework.context.aot.RuntimeHintsBeanFactoryInitializationAotProcessor$RuntimeHintsRegistrarContribution.applyTo(RuntimeHintsBeanFactoryInitializationAotProcessor.java:111)
	at org.springframework.context.aot.BeanFactoryInitializationAotContributions.applyTo(BeanFactoryInitializationAotContributions.java:94)
	at org.springframework.context.aot.ApplicationContextAotGenerator.lambda$processAheadOfTime$0(ApplicationContextAotGenerator.java:59)
	at org.springframework.context.aot.ApplicationContextAotGenerator.withCglibClassHandler(ApplicationContextAotGenerator.java:68)
	at org.springframework.context.aot.ApplicationContextAotGenerator.processAheadOfTime(ApplicationContextAotGenerator.java:54)
	at org.springframework.context.aot.ContextAotProcessor.performAotProcessing(ContextAotProcessor.java:107)
	at org.springframework.context.aot.ContextAotProcessor.doProcess(ContextAotProcessor.java:84)
	at org.springframework.context.aot.ContextAotProcessor.doProcess(ContextAotProcessor.java:49)
	at org.springframework.context.aot.AbstractAotProcessor.process(AbstractAotProcessor.java:84)
	at org.springframework.boot.SpringApplicationAotProcessor.main(SpringApplicationAotProcessor.java:96)
Caused by: java.lang.ClassNotFoundException: org.apache.http.impl.auth.BasicScheme
	at java.base/jdk.internal.loader.BuiltinClassLoader.loadClass(BuiltinClassLoader.java:580)
	at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:490)
	... 13 more

Root Cause

The issue originates from ElasticsearchClientRuntimeHints.java at line 46, which attempts to register Apache HttpClient 4.x classes for serialization:

hints.serialization()
    .registerType(org.apache.http.impl.auth.BasicScheme.class)
    .registerType(org.apache.http.impl.auth.RFC2617Scheme.class)
    .registerType(java.util.HashMap.class);

However, Elasticsearch Java Client 8.x has migrated from Apache HttpClient 4.x to HttpClient 5.x, which uses different package names:

• Old (HttpClient 4.x): org.apache.http.*
• New (HttpClient 5.x): org.apache.hc.client5.* and org.apache.hc.core5.*

Gradle Dependencies

dependencies {
    implementation("org.springframework.boot:spring-boot-starter-data-elasticsearch")
    // ... other dependencies
}

Expected Behavior

AOT processing should complete successfully without requiring Apache HttpClient 4.x classes.

Actual Behavior

AOT processing fails with NoClassDefFoundError because the referenced classes no longer exist in the classpath.

[sothawo]

Thanks for finding this. Will get to it tomorrow after work.

[sothawo]

When building a native test app after the fix that checks if the class is available on the class path, I noticed that I don't need to add anything to the serialization hints for the new client.

@mingchiuli when you add the old libraries to the pom/gradle build, so that the AOT processing does not fail,do you need to add anything from the httpclient classes to get yor applicaiton up and running?

I could add the org.apache.hc.client5.http.impl.auth.BasicScheme, but there is no more RFC2617Scheme in client5; and if it's not needed I would not add it to the aot setup.

[mingchiuli]

When building a native test app after the fix that checks if the class is available on the class path, I noticed that I don't need to add anything to the serialization hints for the new client.

@mingchiuli when you add the old libraries to the pom/gradle build, so that the AOT processing does not fail,do you need to add anything from the httpclient classes to get yor applicaiton up and running?

I could add the org.apache.hc.client5.http.impl.auth.BasicScheme, but there is no more RFC2617Scheme in client5; and if it's not needed I would not add it to the aot setup.

I think you can shake off these historical burdens because Spring Boot 4 itself has many break changes

[sothawo]

Backported to branch 6.0.x