SpringBoot学习笔记(五):SpringBoot与SpringMvc

一、自动配置机制WebMvcAutoConfiguration

通过分析@EnableAutoConfiguration注解知道，Spring会用SpringFatoriesLoader载入一些配置，WebMvcAutoConfiguration是Boot-AutoConfigure自动载入的其中一个用于处理Web

1、 EnableAutoConfigurationAuto-configuration for  EnableWebMvc WebMVC，会载入这个配置

2、@Configuration的嵌入机制，如果添加在一个类中的静态内部类中，这个static内部类会作为子配置被解析

3、WebMvcAutoConfiguration中的两个静态内部类WebMvcAutoConfigurationAdapter和EnableWebMvcConfiguration

    @Configuration

      @Import(EnableWebMvcConfiguration.class)

      @EnableConfigurationProperties({WebMvcProperties.class, ResourceProperties.class })

       public static classWebMvcAutoConfigurationAdapter extends WebMvcConfigurerAdapter

 4、@Configuration

     EnableWebMvcConfigurationextends DelegatingWebMvcConfiguration

 5、总结：相当于传统的MvcConfig用户配置,用@EnableWebMvc修饰一个@Configuration

      EnableWebMvcConfiguration相当于@EnableWebMvc（DelegatingWebMvcConfiguration也是被@EnableWebMvc导入的），

     WebMvcAutoConfigurationAdapter相当于用户自 定义配置（继承WebMvcConfigurerAdapter）

二、WebMvcAutoConfiguration中的详细内容

（一）静态资源处理

1、这个静态资源处理的框架是由WebMvcConfigurationSupport的一个Bean定义的，源码如下

/**

 * Return a handler mapping ordered atInteger.MAX_VALUE-1 with mapped

 * resource handlers. To configure resourcehandling, override

 * {@link #addResourceHandlers}.

 */

@Bean

publicHandlerMapping resourceHandlerMapping() {

ResourceHandlerRegistryregistry = new ResourceHandlerRegistry(this.applicationContext,

this.servletContext,mvcContentNegotiationManager());

addResourceHandlers(registry);

 

AbstractHandlerMappinghandlerMapping = registry.getHandlerMapping();

if(handlerMapping != null) {

handlerMapping.setPathMatcher(mvcPathMatcher());

handlerMapping.setUrlPathHelper(mvcUrlPathHelper());

handlerMapping.setInterceptors(newResourceUrlProviderExposingInterceptor(mvcResourceUrlProvider()));

handlerMapping.setCorsConfigurations(getCorsConfigurations());

}

else{

handlerMapping= new EmptyHandlerMapping();

}

returnhandlerMapping;

}

2、@EnableWebMvc和EnableWebMvcConfiguration继承模板框架类

    子类（WebMvcAutoConfigurationAdapter）通过适配器模式重载addResourceHandlers(registry)，完成扩展

3、适配器WebMvcAutoConfigurationAdapter载入外部配置（SpringBoot默认配置）

    使用@EnableConfigurationProperties和@ConfigurationPropertis机制，为两个Component

     ResourceProperties和WebMvcProperties装配属性（原理请参考笔记二）

4、ResourceProperties内容

String[]SERVLET_RESOURCE_LOCATIONS = { "/" };

 

String[]CLASSPATH_RESOURCE_LOCATIONS = {

"classpath:/META-INF/resources/","classpath:/resources/",

"classpath:/static/","classpath:/public/" };

 

String[]RESOURCE_LOCATIONS;

 

static{

RESOURCE_LOCATIONS= new String[CLASSPATH_RESOURCE_LOCATIONS.length

+SERVLET_RESOURCE_LOCATIONS.length];

System.arraycopy(SERVLET_RESOURCE_LOCATIONS,0, RESOURCE_LOCATIONS, 0,

SERVLET_RESOURCE_LOCATIONS.length);

System.arraycopy(CLASSPATH_RESOURCE_LOCATIONS,0, RESOURCE_LOCATIONS,

SERVLET_RESOURCE_LOCATIONS.length,CLASSPATH_RESOURCE_LOCATIONS.length);

}

//Enable default resource handling.

booleanaddMappings = true;

 5、使用默认属性注册ResourceHandlers

public void addResourceHandlers(ResourceHandlerRegistry registry) {

if (!this.resourceProperties.isAddMappings()) {

logger.debug("Default resource handling disabled");

return;

}

Integer cachePeriod = this.resourceProperties.getCachePeriod();

if (!registry.hasMappingForPattern("/webjars/**")) {

customizeResourceHandlerRegistration(

registry.addResourceHandler("/webjars/**")

.addResourceLocations(

"classpath:/META-INF/resources/webjars/")

.setCachePeriod(cachePeriod));

}

//映射规则:/**

String staticPathPattern =this.mvcProperties.getStaticPathPattern();

if (!registry.hasMappingForPattern(staticPathPattern)) {

customizeResourceHandlerRegistration(

registry.addResourceHandler(staticPathPattern)

.addResourceLocations(

//映射位置

this.resourceProperties.getStaticLocations())

.setCachePeriod(cachePeriod));

 

//最后相当于<mvc:resources mapping="/**" location="classpath:/resources"/>

//<mvc:resources  mapping="/**"  location="classpath:/static/"/>

//<mvc:resources  mapping="/**"  location="classpath:/public/"/>

}

}