02、SpringMVC源码分析 - DispatcherServletAutoConfiguration
DispatcherServletAutoConfiguration
配置类中包含了四个内部类：
1、DispatcherServletConfiguration：用于注册DispatcherServlet和MultipartResolver
2、DispatcherServletRegistrationConfiguration ：用于注册DispatcherServletRegistrationBean
3、DefaultDispatcherServletCondition ：DispatcherServletConfiguration配置类的前置条件
4、DispatcherServletRegistrationCondition ：DispatcherServletRegistrationConfiguration配置类的前置条件
代码如下：
//自动配置顺序
@AutoConfigureOrder(Ordered.HIGHEST_PRECEDENCE)
//配置类
@Configuration(proxyBeanMethods = false)
//servlet的web应用环境
@ConditionalOnWebApplication(type = Type.SERVLET)
//类路径下要有DispatcherServlet
@ConditionalOnClass(DispatcherServlet.class)
//在ServletWebServerFactoryAutoConfiguration之后自动配置
@AutoConfigureAfter(ServletWebServerFactoryAutoConfiguration.class)
public class DispatcherServletAutoConfiguration {
/**
* The bean name for a DispatcherServlet that will be mapped to the root URL "/".
*/
public static final String DEFAULT_DISPATCHER_SERVLET_BEAN_NAME = "dispatcherServlet";
/**
* The bean name for a ServletRegistrationBean for the DispatcherServlet "/".
*/
public static final String DEFAULT_DISPATCHER_SERVLET_REGISTRATION_BEAN_NAME = "dispatcherServletRegistration";
@Configuration(proxyBeanMethods = false)
//类实例化的条件DefaultDispatcherServletCondition
@Conditional(DefaultDispatcherServletCondition.class)
@ConditionalOnClass(ServletRegistration.class)
//WebMvcProperties保存了前缀为spring.mvc的参数
@EnableConfigurationProperties(WebMvcProperties.class)
protected static class DispatcherServletConfiguration {
//springmvc 的核心控制器 DispatcherServlet
@Bean(name = DEFAULT_DISPATCHER_SERVLET_BEAN_NAME)
public DispatcherServlet dispatcherServlet(WebMvcProperties webMvcProperties) {
//创建DispatcherServlet，从WebMvcProperties中获取一些自定义属性
DispatcherServlet dispatcherServlet = new DispatcherServlet();
dispatcherServlet.setDispatchOptionsRequest(webMvcProperties.isDispatchOptionsRequest());
dispatcherServlet.setDispatchTraceRequest(webMvcProperties.isDispatchTraceRequest());
dispatcherServlet.setThrowExceptionIfNoHandlerFound(webMvcProperties.isThrowExceptionIfNoHandlerFound());
dispatcherServlet.setPublishEvents(webMvcProperties.isPublishRequestHandledEvents());
dispatcherServlet.setEnableLoggingRequestDetails(webMvcProperties.isLogRequestDetails());
return dispatcherServlet;
}
@Bean
//MultipartResolver 在类路径下存在
@ConditionalOnBean(MultipartResolver.class)
//MultipartResolver bean 不存在时
@ConditionalOnMissingBean(name = DispatcherServlet.MULTIPART_RESOLVER_BEAN_NAME)
public MultipartResolver multipartResolver(MultipartResolver resolver) {
// Detect if the user has created a MultipartResolver but named it incorrectly
return resolver;
}
}
//配置类
@Configuration(proxyBeanMethods = false)
//前置条件DispatcherServletRegistrationCondition
@Conditional(DispatcherServletRegistrationCondition.class)
//ServletRegistration在类路径下存在
@ConditionalOnClass(ServletRegistration.class)
@EnableConfigurationProperties(WebMvcProperties.class)
//导入配置类DispatcherServletConfiguration
@Import(DispatcherServletConfiguration.class)
//创建DispatcherServletRegistrationBean，注册DispatcherServlet
protected static class DispatcherServletRegistrationConfiguration {
@Bean(name = DEFAULT_DISPATCHER_SERVLET_REGISTRATION_BEAN_NAME)
@ConditionalOnBean(value = DispatcherServlet.class, name = DEFAULT_DISPATCHER_SERVLET_BEAN_NAME)
public DispatcherServletRegistrationBean dispatcherServletRegistration(DispatcherServlet dispatcherServlet,
WebMvcProperties webMvcProperties, ObjectProvider<MultipartConfigElement> multipartConfig) {
DispatcherServletRegistrationBean registration = new DispatcherServletRegistrationBean(dispatcherServlet,
webMvcProperties.getServlet().getPath());
registration.setName(DEFAULT_DISPATCHER_SERVLET_BEAN_NAME);
registration.setLoadOnStartup(webMvcProperties.getServlet().getLoadOnStartup());
multipartConfig.ifAvailable(registration::setMultipartConfig);
return registration;
}
}
//DefaultDispatcherServletCondition 用于校验环境中是否存在DispatcherServlet，不存在时返回true，自动配置DispatcherServlet
@Order(Ordered.LOWEST_PRECEDENCE - 10)
private static class DefaultDispatcherServletCondition extends SpringBootCondition {
@Override
public ConditionOutcome getMatchOutcome(ConditionContext context, AnnotatedTypeMetadata metadata) {
ConditionMessage.Builder message = ConditionMessage.forCondition("Default DispatcherServlet");
ConfigurableListableBeanFactory beanFactory = context.getBeanFactory();
//通过类型查找dispatchServlet
List<String> dispatchServletBeans = Arrays
.asList(beanFactory.getBeanNamesForType(DispatcherServlet.class, false, false));
if (dispatchServletBeans.contains(DEFAULT_DISPATCHER_SERVLET_BEAN_NAME)) {
return ConditionOutcome
.noMatch(message.found("dispatcher servlet bean").items(DEFAULT_DISPATCHER_SERVLET_BEAN_NAME));
}
//通过名字查找dispatchServlet
if (beanFactory.containsBean(DEFAULT_DISPATCHER_SERVLET_BEAN_NAME)) {
return ConditionOutcome.noMatch(
message.found("non dispatcher servlet bean").items(DEFAULT_DISPATCHER_SERVLET_BEAN_NAME));
}
if (dispatchServletBeans.isEmpty()) {
return ConditionOutcome.match(message.didNotFind("dispatcher servlet beans").atAll());
}
return ConditionOutcome.match(message.found("dispatcher servlet bean", "dispatcher servlet beans")
.items(Style.QUOTE, dispatchServletBeans)
.append("and none is named " + DEFAULT_DISPATCHER_SERVLET_BEAN_NAME));
}
}
//DispatcherServletRegistrationCondition 用于校验环境中是否存在DispatcherServletRegistrationBean，不存在时返回true，自动配置DispatcherServletRegistrationBean
@Order(Ordered.LOWEST_PRECEDENCE - 10)
private static class DispatcherServletRegistrationCondition extends SpringBootCondition {
@Override
public ConditionOutcome getMatchOutcome(ConditionContext context, AnnotatedTypeMetadata metadata) {
ConfigurableListableBeanFactory beanFactory = context.getBeanFactory();
//检查dispatcherServlet是否存在
ConditionOutcome outcome = checkDefaultDispatcherName(beanFactory);
if (!outcome.isMatch()) {
return outcome;
}
//检查dispatcherServletRegistration是否存在
return checkServletRegistration(beanFactory);
}
private ConditionOutcome checkDefaultDispatcherName(ConfigurableListableBeanFactory beanFactory) {
boolean containsDispatcherBean = beanFactory.containsBean(DEFAULT_DISPATCHER_SERVLET_BEAN_NAME);
if (!containsDispatcherBean) {
return ConditionOutcome.match();
}
List<String> servlets = Arrays
.asList(beanFactory.getBeanNamesForType(DispatcherServlet.class, false, false));
if (!servlets.contains(DEFAULT_DISPATCHER_SERVLET_BEAN_NAME)) {
return ConditionOutcome.noMatch(
startMessage().found("non dispatcher servlet").items(DEFAULT_DISPATCHER_SERVLET_BEAN_NAME));
}
return ConditionOutcome.match();
}
private ConditionOutcome checkServletRegistration(ConfigurableListableBeanFactory beanFactory) {
ConditionMessage.Builder message = startMessage();
List<String> registrations = Arrays
.asList(beanFactory.getBeanNamesForType(ServletRegistrationBean.class, false, false));
boolean containsDispatcherRegistrationBean = beanFactory
.containsBean(DEFAULT_DISPATCHER_SERVLET_REGISTRATION_BEAN_NAME);
if (registrations.isEmpty()) {
if (containsDispatcherRegistrationBean) {
return ConditionOutcome.noMatch(message.found("non servlet registration bean")
.items(DEFAULT_DISPATCHER_SERVLET_REGISTRATION_BEAN_NAME));
}
return ConditionOutcome.match(message.didNotFind("servlet registration bean").atAll());
}
if (registrations.contains(DEFAULT_DISPATCHER_SERVLET_REGISTRATION_BEAN_NAME)) {
return ConditionOutcome.noMatch(message.found("servlet registration bean")
.items(DEFAULT_DISPATCHER_SERVLET_REGISTRATION_BEAN_NAME));
}
if (containsDispatcherRegistrationBean) {
return ConditionOutcome.noMatch(message.found("non servlet registration bean")
.items(DEFAULT_DISPATCHER_SERVLET_REGISTRATION_BEAN_NAME));
}
return ConditionOutcome.match(message.found("servlet registration beans").items(Style.QUOTE, registrations)
.append("and none is named " + DEFAULT_DISPATCHER_SERVLET_REGISTRATION_BEAN_NAME));
}
private ConditionMessage.Builder startMessage() {
return ConditionMessage.forCondition("DispatcherServlet Registration");
}
}
}