Loading plugin on-runtime : Ambiguous hander methods mapped & ConcurrentModificationException when unregistering routes

[Anton-vanderTuijn]

Hi,

I'm trying to import plugins on-runtime,
I began without on-runtime plugin loading, base on the pf4j-spring demo I manage to create plugins and if I place the plugin file into /plugins before creating the Spring ApplicationContext everything is fine, I can access each of my mapped routes.
To implement on-runtime plugin loading, when I detect a new plugin I load them and then call the following méthod:

public void registerMvcEndpoints(PluginManager pm) {
    pm.getExtensions(PluginInterface.class).stream()
                .flatMap(g -> g.mvcControllers().stream())
                .forEach(r -> {
                    if (!beanAlreadyRegistered.contains(r.getClass().getName())){
                        ((ConfigurableBeanFactory) beanFactory).registerSingleton(r.getClass().getName(), r);
                        beanAlreadyRegistered.add(r.getClass().getName());
                    }
                });
    applicationContext
                .getBeansOfType(RequestMappingHandlerMapping.class)
                .forEach((k, v) -> {
                    v.afterPropertiesSet();
                });

But when I try to access a route, even without adding a plugin I get IllegalStateException: Ambiguous handler methods mapped for ...
That is because the routes are registered a second time, so because of that I try to use unregisterMapping() to clean the mapping by adding the following code:

RequestMappingHandlerMapping requestMappingHandlerMapping = applicationContext.getBean(RequestMappingHandlerMapping.class);
Map<RequestMappingInfo, HandlerMethod> handlerMethods = requestMappingHandlerMapping.getHandlerMethods();
for (RequestMappingInfo key : handlerMethods.keySet()) {
    requestMappingHandlerMapping.unregisterMapping(key);
}

But I get this exception:

org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'pluginEndpoints' defined in class path resource [fr/polytech/al3/PolyVilleActive/PluginConfig.class]: Bean instantiation via factory method failed; nested exception is org.springframework.beans.BeanInstantiationException: Failed to instantiate [int]: Factory method 'pluginEndpoints' threw exception; nested exception is java.util.ConcurrentModificationException
        at org.springframework.beans.factory.support.ConstructorResolver.instantiate(ConstructorResolver.java:656) ~[spring-beans-5.2.5.RELEASE.jar!/:5.2.5.RELEASE]
        at org.springframework.beans.factory.support.ConstructorResolver.instantiateUsingFactoryMethod(ConstructorResolver.java:636) ~[spring-beans-5.2.5.RELEASE.jar!/:5.2.5.RELEASE]
        at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.instantiateUsingFactoryMethod(AbstractAutowireCapableBeanFactory.java:1338) ~[spring-beans-5.2.5.RELEASE.jar!/:5.2.5.RELEASE]
        at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBeanInstance(AbstractAutowireCapableBeanFactory.java:1177) ~[spring-beans-5.2.5.RELEASE.jar!/:5.2.5.RELEASE]
        at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:557) ~[spring-beans-5.2.5.RELEASE.jar!/:5.2.5.RELEASE]
        at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:517) ~[spring-beans-5.2.5.RELEASE.jar!/:5.2.5.RELEASE]
        at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:323) ~[spring-beans-5.2.5.RELEASE.jar!/:5.2.5.RELEASE]
        at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:222) ~[spring-beans-5.2.5.RELEASE.jar!/:5.2.5.RELEASE]
        at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:321) ~[spring-beans-5.2.5.RELEASE.jar!/:5.2.5.RELEASE]
        at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:202) ~[spring-beans-5.2.5.RELEASE.jar!/:5.2.5.RELEASE]
        at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:882) ~[spring-beans-5.2.5.RELEASE.jar!/:5.2.5.RELEASE]
        at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:878) ~[spring-context-5.2.5.RELEASE.jar!/:5.2.5.RELEASE]
        at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:550) ~[spring-context-5.2.5.RELEASE.jar!/:5.2.5.RELEASE]
        at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.refresh(ServletWebServerApplicationContext.java:141) ~[spring-boot-2.2.6.RELEASE.jar!/:2.2.6.RELEASE]
        at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:747) ~[spring-boot-2.2.6.RELEASE.jar!/:2.2.6.RELEASE]
        at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:397) ~[spring-boot-2.2.6.RELEASE.jar!/:2.2.6.RELEASE]
        at org.springframework.boot.SpringApplication.run(SpringApplication.java:315) ~[spring-boot-2.2.6.RELEASE.jar!/:2.2.6.RELEASE]
        at org.springframework.boot.SpringApplication.run(SpringApplication.java:1226) ~[spring-boot-2.2.6.RELEASE.jar!/:2.2.6.RELEASE]
        at org.springframework.boot.SpringApplication.run(SpringApplication.java:1215) ~[spring-boot-2.2.6.RELEASE.jar!/:2.2.6.RELEASE]
        at fr.polytech.al3.PolyVilleActive.SpringPluginContainerApplication.main(SpringPluginContainerApplication.java:29) ~[classes!/:0.0.1-SNAPSHOT]
        at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:na]
        at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:na]
        at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:na]
        at java.base/java.lang.reflect.Method.invoke(Method.java:566) ~[na:na]
        at org.springframework.boot.loader.MainMethodRunner.run(MainMethodRunner.java:48) ~[spring-plugin-container-0.0.1-SNAPSHOT.jar:0.0.1-SNAPSHOT]
        at org.springframework.boot.loader.Launcher.launch(Launcher.java:87) ~[spring-plugin-container-0.0.1-SNAPSHOT.jar:0.0.1-SNAPSHOT]
        at org.springframework.boot.loader.Launcher.launch(Launcher.java:51) ~[spring-plugin-container-0.0.1-SNAPSHOT.jar:0.0.1-SNAPSHOT]
        at org.springframework.boot.loader.JarLauncher.main(JarLauncher.java:52) ~[spring-plugin-container-0.0.1-SNAPSHOT.jar:0.0.1-SNAPSHOT]
Caused by: org.springframework.beans.BeanInstantiationException: Failed to instantiate [int]: Factory method 'pluginEndpoints' threw exception; nested exception is java.util.ConcurrentModificationException
        at org.springframework.beans.factory.support.SimpleInstantiationStrategy.instantiate(SimpleInstantiationStrategy.java:185) ~[spring-beans-5.2.5.RELEASE.jar!/:5.2.5.RELEASE]
        at org.springframework.beans.factory.support.ConstructorResolver.instantiate(ConstructorResolver.java:651) ~[spring-beans-5.2.5.RELEASE.jar!/:5.2.5.RELEASE]
        ... 27 common frames omitted
Caused by: java.util.ConcurrentModificationException: null
        at java.base/java.util.LinkedHashMap$LinkedHashIterator.nextNode(LinkedHashMap.java:719) ~[na:na]
        at java.base/java.util.LinkedHashMap$LinkedKeyIterator.next(LinkedHashMap.java:741) ~[na:na]
        at java.base/java.util.Collections$UnmodifiableCollection$1.next(Collections.java:1047) ~[na:na]
        at fr.polytech.al3.PolyVilleActive.PluginConfig.registerMvcEndpoints(PluginConfig.java:81) ~[classes!/:0.0.1-SNAPSHOT]
        at fr.polytech.al3.PolyVilleActive.PluginConfig.pluginEndpoints(PluginConfig.java:54) ~[classes!/:0.0.1-SNAPSHOT]
        at fr.polytech.al3.PolyVilleActive.PluginConfig$$EnhancerBySpringCGLIB$$7f069b53.CGLIB$pluginEndpoints$2(<generated>) ~[classes!/:0.0.1-SNAPSHOT]
        at fr.polytech.al3.PolyVilleActive.PluginConfig$$EnhancerBySpringCGLIB$$7f069b53$$FastClassBySpringCGLIB$$c0fdb9ae.invoke(<generated>) ~[classes!/:0.0.1-SNAPSHOT]
        at org.springframework.cglib.proxy.MethodProxy.invokeSuper(MethodProxy.java:244) ~[spring-core-5.2.5.RELEASE.jar!/:5.2.5.RELEASE]
        at org.springframework.context.annotation.ConfigurationClassEnhancer$BeanMethodInterceptor.intercept(ConfigurationClassEnhancer.java:331) ~[spring-context-5.2.5.RELEASE.jar!/:5.2.5.RELEASE]
        at fr.polytech.al3.PolyVilleActive.PluginConfig$$EnhancerBySpringCGLIB$$7f069b53.pluginEndpoints(<generated>) ~[classes!/:0.0.1-SNAPSHOT]
        at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:na]
        at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:na]
        at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:na]
        at java.base/java.lang.reflect.Method.invoke(Method.java:566) ~[na:na]
        at org.springframework.beans.factory.support.SimpleInstantiationStrategy.instantiate(SimpleInstantiationStrategy.java:154) ~[spring-beans-5.2.5.RELEASE.jar!/:5.2.5.RELEASE]
        ... 28 common frames omitted