NoClassDefFoundError with Reactor 2.0.0.M2

[jbcpollak]

In Reactor 2.0.0.M2 the Environment class was moved from reactor.core.Environment to reactor.Environment. This causes the following error and the Spring context cannot be started:

Caused by: java.lang.NoClassDefFoundError: reactor/core/Environment
    at java.lang.Class.getDeclaredMethods0(Native Method) ~[na:1.8.0_25]
    at java.lang.Class.privateGetDeclaredMethods(Class.java:2693) ~[na:1.8.0_25]
    at java.lang.Class.getDeclaredMethods(Class.java:1967) ~[na:1.8.0_25]
    at org.springframework.util.ReflectionUtils.getDeclaredMethods(ReflectionUtils.java:571) ~[spring-core-4.1.3.RELEASE.jar:4.1.3.RELEASE]
    at org.springframework.util.ReflectionUtils.doWithMethods(ReflectionUtils.java:490) ~[spring-core-4.1.3.RELEASE.jar:4.1.3.RELEASE]
    at org.springframework.util.ReflectionUtils.doWithMethods(ReflectionUtils.java:474) ~[spring-core-4.1.3.RELEASE.jar:4.1.3.RELEASE]
    at org.springframework.util.ReflectionUtils.getUniqueDeclaredMethods(ReflectionUtils.java:534) ~[spring-core-4.1.3.RELEASE.jar:4.1.3.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.getTypeForFactoryMethod(AbstractAutowireCapableBeanFactory.java:677) ~[spring-beans-4.1.3.RELEASE.jar:4.1.3.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.determineTargetType(AbstractAutowireCapableBeanFactory.java:621) ~[spring-beans-4.1.3.RELEASE.jar:4.1.3.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.predictBeanType(AbstractAutowireCapableBeanFactory.java:591) ~[spring-beans-4.1.3.RELEASE.jar:4.1.3.RELEASE]
    at org.springframework.beans.factory.support.AbstractBeanFactory.isFactoryBean(AbstractBeanFactory.java:1386) ~[spring-beans-4.1.3.RELEASE.jar:4.1.3.RELEASE]
    at org.springframework.beans.factory.support.AbstractBeanFactory.isFactoryBean(AbstractBeanFactory.java:957) ~[spring-beans-4.1.3.RELEASE.jar:4.1.3.RELEASE]
    at org.springframework.boot.autoconfigure.condition.BeanTypeRegistry$OptimizedBeanTypeRegistry.addBeanTypeForNonAliasDefinition(BeanTypeRegistry.java:257) ~[spring-boot-autoconfigure-1.2.0.RELEASE.jar:1.2.0.RELEASE]
    at org.springframework.boot.autoconfigure.condition.BeanTypeRegistry$OptimizedBeanTypeRegistry.addBeanType(BeanTypeRegistry.java:246) ~[spring-boot-autoconfigure-1.2.0.RELEASE.jar:1.2.0.RELEASE]
    at org.springframework.boot.autoconfigure.condition.BeanTypeRegistry$OptimizedBeanTypeRegistry.getNamesForType(BeanTypeRegistry.java:227) ~[spring-boot-autoconfigure-1.2.0.RELEASE.jar:1.2.0.RELEASE]
    at org.springframework.boot.autoconfigure.condition.OnBeanCondition.collectBeanNamesForType(OnBeanCondition.java:154) ~[spring-boot-autoconfigure-1.2.0.RELEASE.jar:1.2.0.RELEASE]
    at org.springframework.boot.autoconfigure.condition.OnBeanCondition.getBeanNamesForType(OnBeanCondition.java:143) ~[spring-boot-autoconfigure-1.2.0.RELEASE.jar:1.2.0.RELEASE]
    at org.springframework.boot.autoconfigure.condition.OnBeanCondition.getMatchingBeans(OnBeanCondition.java:115) ~[spring-boot-autoconfigure-1.2.0.RELEASE.jar:1.2.0.RELEASE]
    at org.springframework.boot.autoconfigure.condition.OnBeanCondition.getMatchOutcome(OnBeanCondition.java:90) ~[spring-boot-autoconfigure-1.2.0.RELEASE.jar:1.2.0.RELEASE]
    at org.springframework.boot.autoconfigure.condition.SpringBootCondition.matches(SpringBootCondition.java:45) ~[spring-boot-autoconfigure-1.2.0.RELEASE.jar:1.2.0.RELEASE]
    ... 40 common frames omitted
Caused by: java.lang.ClassNotFoundException: reactor.core.Environment
    at java.net.URLClassLoader$1.run(URLClassLoader.java:372) ~[na:1.8.0_25]
    at java.net.URLClassLoader$1.run(URLClassLoader.java:361) ~[na:1.8.0_25]
    at java.security.AccessController.doPrivileged(Native Method) ~[na:1.8.0_25]
    at java.net.URLClassLoader.findClass(URLClassLoader.java:360) ~[na:1.8.0_25]
    at java.lang.ClassLoader.loadClass(ClassLoader.java:424) ~[na:1.8.0_25]
    at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:308) ~[na:1.8.0_25]
    at java.lang.ClassLoader.loadClass(ClassLoader.java:357) ~[na:1.8.0_25]
    ... 60 common frames omitted

[jbcpollak]

For people looking for a temporary work around, my solution for this was to create stub reactor.core.Environment and reactor.core.Reactor classes in my project (no body needed, just stub classes).

Then I cloned ReactorAutoConfiguration from Spring-Boot and modify it like this:

package com.assuredlabor.caipirinha.configuration;

import org.springframework.boot.autoconfigure.AutoConfigureAfter;
import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;
import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;
import org.springframework.boot.autoconfigure.web.WebMvcAutoConfiguration;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

import reactor.Environment;
import reactor.bus.EventBus;
import reactor.core.Reactor;
import reactor.spring.context.config.EnableReactor;

@Configuration
@ConditionalOnClass(EnableReactor.class)
@AutoConfigureAfter(WebMvcAutoConfiguration.class)
public class ReactorAutoConfiguration {

    @Bean
    public Reactor stubReactor() {
        return new Reactor();
    }

    @Bean
    public reactor.core.Environment stubEnvironment() {
        return new reactor.core.Environment();
    }

    @Bean
    @ConditionalOnMissingBean(EventBus.class)
    public EventBus rootBus(Environment environment) {
        return environment.getRootBus();
    }

    @Configuration
    @ConditionalOnMissingBean(Environment.class)
    @EnableReactor
    protected static class ReactorConfiguration {
    }
}

The stub beans effectively disable the existing Spring-Boot auto configuration.

[philwebb]

Do you have an example application that I could try? The @ConditionalOnClass annotation on the ReactorAutoConfiguration should guard against missing classes. You could also try using @EnableAutoConfiguration(exclude=ReactorAutoConfiguration.class) which might be a bit nicer then creating those stub classes.

[philwebb]

/cc @jbrisbin

[jbcpollak]

@philwebb - I think the issue is the @ConditionalOnClass checks for the EnableReactor.class, which didn't change package locations, so that executes, and then the @ConditionalOnMissingBean(Environment.class) tries to create a reactor.core.Environment which doesn't exist.

I guess another solution would be for the Reactor project to move EnableReactor to another class, and then Spring-Boot could have separate ReactorAutoConfiguration classes for 1.x and 2.x.

I'll try your exclude suggestion, that sounds cleaner.

[philwebb]

Ahh OK. Looks like we've added an additional guard in Spring Boot 1.2 for this (see 80d55c4) but it's not been applied to 1.1.x. I'll back-port it.

[jbcpollak]

@philwebb - I'm using Spring Boot 1.2.0-RELEASE, that guard isn't in that release. Looks like it is in 1.2.1-SNAPSHOT though.

[philwebb]

My mistake, it looks like we introduced that after 1.2.0. The fix will be in the upcoming 1.2.1. release.