聊聊springboot2的MappingsEndpoint

序

本文主要研究下springboot2的MappingsEndpoint

MappingsEndpointAutoConfiguration

spring-boot-actuator-autoconfigure-2.0.1.RELEASE-sources.jar!/org/springframework/boot/actuate/autoconfigure/web/mappings/MappingsEndpointAutoConfiguration.java

@ManagementContextConfiguration
public class MappingsEndpointAutoConfiguration {

    @Bean
    @ConditionalOnEnabledEndpoint
    public MappingsEndpoint mappingsEndpoint(ApplicationContext applicationContext,
            ObjectProvider<Collection<MappingDescriptionProvider>> descriptionProviders) {
        return new MappingsEndpoint(
                descriptionProviders.getIfAvailable(Collections::emptyList),
                applicationContext);
    }

    @Configuration
    @ConditionalOnWebApplication(type = Type.SERVLET)
    static class ServletWebConfiguration {

        @Bean
        ServletsMappingDescriptionProvider servletMappingDescriptionProvider() {
            return new ServletsMappingDescriptionProvider();
        }

        @Bean
        FiltersMappingDescriptionProvider filterMappingDescriptionProvider() {
            return new FiltersMappingDescriptionProvider();
        }

        @Configuration
        @ConditionalOnClass(DispatcherServlet.class)
        @ConditionalOnBean(DispatcherServlet.class)
        static class SpringMvcConfiguration {

            @Bean
            DispatcherServletsMappingDescriptionProvider dispatcherServletMappingDescriptionProvider() {
                return new DispatcherServletsMappingDescriptionProvider();
            }

        }

    }

    @Configuration
    @ConditionalOnWebApplication(type = Type.REACTIVE)
    @ConditionalOnClass(DispatcherHandler.class)
    @ConditionalOnBean(DispatcherHandler.class)
    static class ReactiveWebConfiguration {

        @Bean
        public DispatcherHandlersMappingDescriptionProvider dispatcherHandlerMappingDescriptionProvider(
                ApplicationContext applicationContext) {
            return new DispatcherHandlersMappingDescriptionProvider();
        }

    }

}

这里使用descriptionProviders创建mappingsEndpoint，然后根据是servlet或reactive的方式来创建不同的MappingDescriptionProvider，servlet创建的是ServletsMappingDescriptionProvider，FiltersMappingDescriptionProvider，DispatcherServletsMappingDescriptionProvider，reactive创建的是DispatcherHandlersMappingDescriptionProvider

MappingsEndpoint

spring-boot-actuator-2.0.1.RELEASE-sources.jar!/org/springframework/boot/actuate/web/mappings/MappingsEndpoint.java

@Endpoint(id = "mappings")
public class MappingsEndpoint {

    private final Collection<MappingDescriptionProvider> descriptionProviders;

    private final ApplicationContext context;

    public MappingsEndpoint(Collection<MappingDescriptionProvider> descriptionProviders,
            ApplicationContext context) {
        this.descriptionProviders = descriptionProviders;
        this.context = context;
    }

    @ReadOperation
    public ApplicationMappings mappings() {
        ApplicationContext target = this.context;
        Map<String, ContextMappings> contextMappings = new HashMap<>();
        while (target != null) {
            contextMappings.put(target.getId(), mappingsForContext(target));
            target = target.getParent();
        }
        return new ApplicationMappings(contextMappings);
    }

    private ContextMappings mappingsForContext(ApplicationContext applicationContext) {
        Map<String, Object> mappings = new HashMap<>();
        this.descriptionProviders
                .forEach((provider) -> mappings.put(provider.getMappingName(),
                        provider.describeMappings(applicationContext)));
        return new ContextMappings(mappings, applicationContext.getParent() == null ? null
                : applicationContext.getId());
    }
    //......
}

这里根据descriptionProviders创建ContextMappings

servlet方式

ServletsMappingDescriptionProvider

spring-boot-actuator-2.0.1.RELEASE-sources.jar!/org/springframework/boot/actuate/web/mappings/servlet/ServletsMappingDescriptionProvider.java

public class ServletsMappingDescriptionProvider implements MappingDescriptionProvider {

    @Override
    public List<ServletRegistrationMappingDescription> describeMappings(
            ApplicationContext context) {
        if (!(context instanceof WebApplicationContext)) {
            return Collections.emptyList();
        }
        return ((WebApplicationContext) context).getServletContext()
                .getServletRegistrations().values().stream()
                .map(ServletRegistrationMappingDescription::new)
                .collect(Collectors.toList());
    }

    @Override
    public String getMappingName() {
        return "servlets";
    }

}

这里从servletContext中获取ServletRegistrations，再获取ServletRegistrationMappingDescription

FiltersMappingDescriptionProvider

spring-boot-actuator-2.0.1.RELEASE-sources.jar!/org/springframework/boot/actuate/web/mappings/servlet/FiltersMappingDescriptionProvider.java

public class FiltersMappingDescriptionProvider implements MappingDescriptionProvider {

    @Override
    public List<FilterRegistrationMappingDescription> describeMappings(
            ApplicationContext context) {
        if (!(context instanceof WebApplicationContext)) {
            return Collections.emptyList();
        }
        return ((WebApplicationContext) context).getServletContext()
                .getFilterRegistrations().values().stream()
                .map(FilterRegistrationMappingDescription::new)
                .collect(Collectors.toList());
    }

    @Override
    public String getMappingName() {
        return "servletFilters";
    }

}

这里从servletContext中获取FilterRegistrations，再获取FilterRegistrationMappingDescription

DispatcherServletsMappingDescriptionProvider

spring-boot-actuator-2.0.1.RELEASE-sources.jar!/org/springframework/boot/actuate/web/mappings/servlet/DispatcherServletsMappingDescriptionProvider.java

public class DispatcherServletsMappingDescriptionProvider
        implements MappingDescriptionProvider {

    private static final List<HandlerMappingDescriptionProvider<? extends HandlerMapping>> descriptionProviders;

    static {
        List<HandlerMappingDescriptionProvider<? extends HandlerMapping>> providers = new ArrayList<>();
        providers.add(new RequestMappingInfoHandlerMappingDescriptionProvider());
        providers.add(new UrlHandlerMappingDescriptionProvider());
        if (ClassUtils.isPresent(
                "org.springframework.data.rest.webmvc.support.DelegatingHandlerMapping",
                null)) {
            providers.add(new DelegatingHandlerMappingDescriptionProvider(
                    new ArrayList<>(providers)));
        }
        descriptionProviders = Collections.unmodifiableList(providers);
    }

    @Override
    public String getMappingName() {
        return "dispatcherServlets";
    }

    @Override
    public Map<String, List<DispatcherServletMappingDescription>> describeMappings(
            ApplicationContext context) {
        if (context instanceof WebApplicationContext) {
            return describeMappings((WebApplicationContext) context);
        }
        return Collections.emptyMap();
    }

    private Map<String, List<DispatcherServletMappingDescription>> describeMappings(
            WebApplicationContext context) {
        Map<String, List<DispatcherServletMappingDescription>> mappings = new HashMap<>();
        context.getBeansOfType(DispatcherServlet.class)
                .forEach((name, dispatcherServlet) -> mappings.put(name,
                        describeMappings(new DispatcherServletHandlerMappings(name,
                                dispatcherServlet, context))));
        return mappings;
    }

    private List<DispatcherServletMappingDescription> describeMappings(
            DispatcherServletHandlerMappings mappings) {
        return mappings.getHandlerMappings().stream().flatMap(this::describe)
                .collect(Collectors.toList());
    }

    private <T extends HandlerMapping> Stream<DispatcherServletMappingDescription> describe(
            T handlerMapping) {
        return describe(handlerMapping, descriptionProviders).stream();
    }

    @SuppressWarnings("unchecked")
    private static <T extends HandlerMapping> List<DispatcherServletMappingDescription> describe(
            T handlerMapping,
            List<HandlerMappingDescriptionProvider<?>> descriptionProviders) {
        for (HandlerMappingDescriptionProvider<?> descriptionProvider : descriptionProviders) {
            if (descriptionProvider.getMappingClass().isInstance(handlerMapping)) {
                return ((HandlerMappingDescriptionProvider<T>) descriptionProvider)
                        .describe(handlerMapping);
            }
        }
        return Collections.emptyList();
    }
    //......
}

这里主要从DelegatingHandlerMappingDescriptionProvider、RequestMappingInfoHandlerMappingDescriptionProvider、UrlHandlerMappingDescriptionProvider获取DispatcherServletMappingDescription

reactive方式

DispatcherHandlersMappingDescriptionProvider

spring-boot-actuator-2.0.1.RELEASE-sources.jar!/org/springframework/boot/actuate/web/mappings/reactive/DispatcherHandlersMappingDescriptionProvider.java

public class DispatcherHandlersMappingDescriptionProvider
        implements MappingDescriptionProvider {

    private static final List<HandlerMappingDescriptionProvider<? extends HandlerMapping>> descriptionProviders = Arrays
            .asList(new RequestMappingInfoHandlerMappingDescriptionProvider(),
                    new UrlHandlerMappingDescriptionProvider(),
                    new RouterFunctionMappingDescriptionProvider());

    @Override
    public String getMappingName() {
        return "dispatcherHandlers";
    }

    @Override
    public Map<String, List<DispatcherHandlerMappingDescription>> describeMappings(
            ApplicationContext context) {
        Map<String, List<DispatcherHandlerMappingDescription>> mappings = new HashMap<>();
        context.getBeansOfType(DispatcherHandler.class).forEach(
                (name, handler) -> mappings.put(name, describeMappings(handler)));
        return mappings;
    }

    private List<DispatcherHandlerMappingDescription> describeMappings(
            DispatcherHandler dispatcherHandler) {
        return dispatcherHandler.getHandlerMappings().stream().flatMap(this::describe)
                .collect(Collectors.toList());
    }

    @SuppressWarnings("unchecked")
    private <T extends HandlerMapping> Stream<DispatcherHandlerMappingDescription> describe(
            T handlerMapping) {
        for (HandlerMappingDescriptionProvider<?> descriptionProvider : descriptionProviders) {
            if (descriptionProvider.getMappingClass().isInstance(handlerMapping)) {
                return ((HandlerMappingDescriptionProvider<T>) descriptionProvider)
                        .describe(handlerMapping).stream();

            }
        }
        return Stream.empty();
    }
    //......
}

与servlet获取DispatcherServletsMappingDescriptionProvider不同，reactive获取的是DispatcherHandlersMappingDescriptionProvider
主要从RequestMappingInfoHandlerMappingDescriptionProvider、RouterFunctionMappingDescriptionProvider、UrlHandlerMappingDescriptionProvider这三个来获取HandlerMappingDescriptionProvider

小结

springboot2的MappingsEndpoint通过provider根据servlet及reactive分别进行各自的mappings获取，servlet主要分为ServletsMappingDescriptionProvider、FiltersMappingDescriptionProvider、DispatcherServletsMappingDescriptionProvider，而reactive主要分为DispatcherHandlersMappingDescriptionProvider

doc

• Spring Boot Reference Guide