springboot初学（五）springmvc自动配置原理
@Configuration
@ConditionalOnWebApplication(type = Type.SERVLET)
@ConditionalOnClass({ Servlet.class, DispatcherServlet.class, WebMvcConfigurer.class })
@ConditionalOnMissingBean(WebMvcConfigurationSupport.class)
@AutoConfigureOrder(Ordered.HIGHEST_PRECEDENCE + 10)
@AutoConfigureAfter({ DispatcherServletAutoConfiguration.class,
TaskExecutionAutoConfiguration.class, ValidationAutoConfiguration.class })
public class WebMvcAutoConfiguration {以上是WebMvcAutoConfiguration 自动配置类。如果我们想要添加额外附加功能，比如 拦截器,转换器，日期格式化器，需要自己添加实现相应的配置类，加入到IOC容器中。
springboot通过WebMvcAutoConfiguration的配置类中的WebMvcAutoConfigurationAdapter内部类，该类可以实现将一些常用的bean 加入到IOC容器中，比如之前说到的 拦截器,转换器，日期格式化器。
那springboot是怎么实现添加我们自己实现的拦截器,转换器，日期格式化器等附加功能呢？
可以看到WebMvcAutoConfigurationAdapter上的注解
看一下该类的源码：EnableWebMvcConfiguration.class
/**
* Configuration equivalent to {@code @EnableWebMvc}.
*/
@Configuration
public static class EnableWebMvcConfiguration extends DelegatingWebMvcConfiguration {
private final WebMvcProperties mvcProperties;
private final ListableBeanFactory beanFactory;
private final WebMvcRegistrations mvcRegistrations;
public EnableWebMvcConfiguration(
ObjectProvider mvcPropertiesProvider,
ObjectProvider mvcRegistrationsProvider,
ListableBeanFactory beanFactory) {
this.mvcProperties = mvcPropertiesProvider.getIfAvailable();
this.mvcRegistrations = mvcRegistrationsProvider.getIfUnique();
this.beanFactory = beanFactory;
}
@Bean
@Override
public RequestMappingHandlerAdapter requestMappingHandlerAdapter() {
RequestMappingHandlerAdapter adapter = super.requestMappingHandlerAdapter();
adapter.setIgnoreDefaultModelOnRedirect(this.mvcProperties == null
|| this.mvcProperties.isIgnoreDefaultModelOnRedirect());
return adapter;
}
@Override
protected RequestMappingHandlerAdapter createRequestMappingHandlerAdapter() {
if (this.mvcRegistrations != null
&& this.mvcRegistrations.getRequestMappingHandlerAdapter() != null) {
return this.mvcRegistrations.getRequestMappingHandlerAdapter();
}
return super.createRequestMappingHandlerAdapter();
}
@Bean
@Primary
@Override
public RequestMappingHandlerMapping requestMappingHandlerMapping() {
// Must be @Primary for MvcUriComponentsBuilder to work
return super.requestMappingHandlerMapping();
}
@Bean
@Override
public FormattingConversionService mvcConversionService() {
WebConversionService conversionService = new WebConversionService(
this.mvcProperties.getDateFormat());
addFormatters(conversionService);
return conversionService;
}
@Bean
@Override
public Validator mvcValidator() {
if (!ClassUtils.isPresent("javax.validation.Validator",
getClass().getClassLoader())) {
return super.mvcValidator();
}
return ValidatorAdapter.get(getApplicationContext(), getValidator());
}
@Override
protected RequestMappingHandlerMapping createRequestMappingHandlerMapping() {
if (this.mvcRegistrations != null
&& this.mvcRegistrations.getRequestMappingHandlerMapping() != null) {
return this.mvcRegistrations.getRequestMappingHandlerMapping();
}
return super.createRequestMappingHandlerMapping();
}
@Override
protected ConfigurableWebBindingInitializer getConfigurableWebBindingInitializer() {
try {
return this.beanFactory.getBean(ConfigurableWebBindingInitializer.class);
}
catch (NoSuchBeanDefinitionException ex) {
return super.getConfigurableWebBindingInitializer();
}
}
@Override
protected ExceptionHandlerExceptionResolver createExceptionHandlerExceptionResolver() {
if (this.mvcRegistrations != null && this.mvcRegistrations
.getExceptionHandlerExceptionResolver() != null) {
return this.mvcRegistrations.getExceptionHandlerExceptionResolver();
}
return super.createExceptionHandlerExceptionResolver();
}
@Override
protected void configureHandlerExceptionResolvers(
List exceptionResolvers) {
super.configureHandlerExceptionResolvers(exceptionResolvers);
if (exceptionResolvers.isEmpty()) {
addDefaultHandlerExceptionResolvers(exceptionResolvers);
}
if (this.mvcProperties.isLogResolvedException()) {
for (HandlerExceptionResolver resolver : exceptionResolvers) {
if (resolver instanceof AbstractHandlerExceptionResolver) {
((AbstractHandlerExceptionResolver) resolver)
.setWarnLogCategory(resolver.getClass().getName());
}
}
}
}
@Bean
@Override
public ContentNegotiationManager mvcContentNegotiationManager() {
ContentNegotiationManager manager = super.mvcContentNegotiationManager();
List strategies = manager.getStrategies();
ListIterator iterator = strategies.listIterator();
while (iterator.hasNext()) {
ContentNegotiationStrategy strategy = iterator.next();
if (strategy instanceof PathExtensionContentNegotiationStrategy) {
iterator.set(new OptionalPathExtensionContentNegotiationStrategy(
strategy));
}
}
return manager;
}
} 这个类可以看到也是一个配置类，可以为IOC容器中添加 RequestMappingHandlerAdapter ， RequestMappingHandlerMapping等等。让我们看一下他的父类：
/*
* Copyright 2002-2016 the original author or authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* https://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.springframework.web.servlet.config.annotation;
import java.util.List;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.annotation.Configuration;
import org.springframework.format.FormatterRegistry;
import org.springframework.http.converter.HttpMessageConverter;
import org.springframework.lang.Nullable;
import org.springframework.util.CollectionUtils;
import org.springframework.validation.MessageCodesResolver;
import org.springframework.validation.Validator;
import org.springframework.web.method.support.HandlerMethodArgumentResolver;
import org.springframework.web.method.support.HandlerMethodReturnValueHandler;
import org.springframework.web.servlet.HandlerExceptionResolver;
/**
* A subclass of {@code WebMvcConfigurationSupport} that detects and delegates
* to all beans of type {@link WebMvcConfigurer} allowing them to customize the
* configuration provided by {@code WebMvcConfigurationSupport}. This is the
* class actually imported by {@link EnableWebMvc @EnableWebMvc}.
*
* @author Rossen Stoyanchev
* @since 3.1
*/
@Configuration
public class DelegatingWebMvcConfiguration extends WebMvcConfigurationSupport {
private final WebMvcConfigurerComposite configurers = new WebMvcConfigurerComposite();
@Autowired(required = false)
public void setConfigurers(List configurers) {
if (!CollectionUtils.isEmpty(configurers)) {
this.configurers.addWebMvcConfigurers(configurers);
}
}
@Override
protected void configurePathMatch(PathMatchConfigurer configurer) {
this.configurers.configurePathMatch(configurer);
}
@Override
protected void configureContentNegotiation(ContentNegotiationConfigurer configurer) {
this.configurers.configureContentNegotiation(configurer);
}
@Override
protected void configureAsyncSupport(AsyncSupportConfigurer configurer) {
this.configurers.configureAsyncSupport(configurer);
}
@Override
protected void configureDefaultServletHandling(DefaultServletHandlerConfigurer configurer) {
this.configurers.configureDefaultServletHandling(configurer);
}
@Override
protected void addFormatters(FormatterRegistry registry) {
this.configurers.addFormatters(registry);
}
@Override
protected void addInterceptors(InterceptorRegistry registry) {
this.configurers.addInterceptors(registry);
}
@Override
protected void addResourceHandlers(ResourceHandlerRegistry registry) {
this.configurers.addResourceHandlers(registry);
}
@Override
protected void addCorsMappings(CorsRegistry registry) {
this.configurers.addCorsMappings(registry);
}
@Override
protected void addViewControllers(ViewControllerRegistry registry) {
this.configurers.addViewControllers(registry);
}
@Override
protected void configureViewResolvers(ViewResolverRegistry registry) {
this.configurers.configureViewResolvers(registry);
}
@Override
protected void addArgumentResolvers(List argumentResolvers) {
this.configurers.addArgumentResolvers(argumentResolvers);
}
@Override
protected void addReturnValueHandlers(List returnValueHandlers) {
this.configurers.addReturnValueHandlers(returnValueHandlers);
}
@Override
protected void configureMessageConverters(List> converters) {
this.configurers.configureMessageConverters(converters);
}
@Override
protected void extendMessageConverters(List> converters) {
this.configurers.extendMessageConverters(converters);
}
@Override
protected void configureHandlerExceptionResolvers(List exceptionResolvers) {
this.configurers.configureHandlerExceptionResolvers(exceptionResolvers);
}
@Override
protected void extendHandlerExceptionResolvers(List exceptionResolvers) {
this.configurers.extendHandlerExceptionResolvers(exceptionResolvers);
}
@Override
@Nullable
protected Validator getValidator() {
return this.configurers.getValidator();
}
@Override
@Nullable
protected MessageCodesResolver getMessageCodesResolver() {
return this.configurers.getMessageCodesResolver();
}
}
主要看其中一个方法：
@Autowired(required = false)
public void setConfigurers(List configurers) {
if (!CollectionUtils.isEmpty(configurers)) {
this.configurers.addWebMvcConfigurers(configurers);
}
} 