trouble_shoot.md

Trouble Shoot

I get ClassNotFoundException

• Solution: Locate the missing class library, and add dependency in the main app project.
• It mainly because SpringBoot instantiate bean by new, in this case the class is load by main app classloader that our of our control.

// org.springframework.boot.autoconfigure.data.AbstractRepositoryConfigurationSourceSupport
@Override
public void registerBeanDefinitions(AnnotationMetadata importingClassMetadata, BeanDefinitionRegistry registry,
        BeanNameGenerator importBeanNameGenerator) {
    RepositoryConfigurationDelegate delegate = new RepositoryConfigurationDelegate(
            getConfigurationSource(registry, importBeanNameGenerator), this.resourceLoader, this.environment);
    delegate.registerRepositoriesIn(registry, getRepositoryConfigurationExtension());
}

I get ClassCastException

• Solution: specify class in plugin.pluginFirstClasses of application.yml
• It's because the class is loaded by mismatch class loader. spring-boot-autoconfigure package referred a lot 3rd party classed directly, which should be loaded by our PluginClassloader in our case.

Irrelevant beans get inject to plugin ApplicationContext

• You need to find out which AutoConfiguration introduce those beans, and add it by getExcluceConfigurations.

    @Override
    protected SpringBootstrap createSpringBootstrap() {
        return new SharedDataSourceSpringBootstrap(this, MdSimplePluginStarter.class) {
            @Override
            protected String[] getExcludeConfigurations() {
                return ArrayUtils.addAll(super.getExcludeConfigurations(),
                        "graphql.spring.web.servlet.GraphQLEndpointConfiguration");
            }
        }
        .addSharedBeanName("extensionRegisterService");
    }

Plugin is not compiled after I changed code.

• If you try to run your app with plugin from IDE, mostly the IDE will only compile the app project/module only. Therefore you have to tell the IDE compile everything including plugin code. for IDEA, you could use this setting of Run/Debug Configuration:

Autowire PluginManager carefully

• Since plugin injects beans from main app, you'd better always use @Lazy with @Autowire for PluginManager together to make sure Spring instantiates all needed beans before it starts to load plugin.

Misc.

• Package name cannot start with org.pf4j, java or javax. PluginClassLoader will treat them differently.
• Stay in same framework stack as long as you can. Introducing library with complex dependencies (link Spring Data JPA) into plugin only, will cause many unexpected problems. Because plugin and app have different classloader, it's a little bit hard to mark sure all referred dependent classes are loaded by the same classloader.