SpringBoot4-Web3-SpringMVC

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扩展SpringMVC

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<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:mvc="http://www.springframework.org/schema/mvc"
       xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd http://www.springframework.org/schema/mvc https://www.springframework.org/schema/mvc/spring-mvc.xsd">
    <mvc:view-controller path="/hello" view-name="succcess"></mvc:view-controller>
    <mvc:interceptors>
        <mvc:interceptor>
            <mvc:mapping path="/hello"/>
            <bean></bean>
        </mvc:interceptor>
    </mvc:interceptors>
</beans>

编写一个配置类（@Configuration）,是WebMvcConfigurerAdapter，不标注@EnableWebMvc 

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package com.wsx.springboothelloworld.config;

import org.springframework.boot.autoconfigure.web.servlet.WebMvcAutoConfiguration;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.servlet.config.annotation.ViewControllerRegistry;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurationSupport;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurerAdapter;

@Configuration
public class MyMvcConfig extends WebMvcConfigurerAdapter {
    @Override
    public void addViewControllers(ViewControllerRegistry registry) {
        super.addViewControllers(registry);
        registry.addViewController("/wsx").setViewName("templates_hello");
    }
}
### 原理 
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@Configuration(proxyBeanMethods = false)
@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 {

    public static final String DEFAULT_PREFIX = "";

    public static final String DEFAULT_SUFFIX = "";

    private static final String[] SERVLET_LOCATIONS = { "/" };
里面也是这个类，注意又个EnableWebMvcConfiguration 
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// Defined as a nested config to ensure WebMvcConfigurer is not read when not
// on the classpath
@Configuration(proxyBeanMethods = false)
@Import(EnableWebMvcConfiguration.class)
@EnableConfigurationProperties({ WebMvcProperties.class, ResourceProperties.class })
@Order(0)
public static class WebMvcAutoConfigurationAdapter implements WebMvcConfigurer {

    private static final Log logger = LogFactory.getLog(WebMvcConfigurer.class);

    private final ResourceProperties resourceProperties;
静态资源映射 
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@Override
public void addResourceHandlers(ResourceHandlerRegistry registry) {
    if (!this.resourceProperties.isAddMappings()) {
        logger.debug("Default resource handling disabled");
        return;
    }
    Duration cachePeriod = this.resourceProperties.getCache().getPeriod();
    CacheControl cacheControl = this.resourceProperties.getCache().getCachecontrol().toHttpCacheControl();
    if (!registry.hasMappingForPattern("/webjars/**")) {
        customizeResourceHandlerRegistration(registry.addResourceHandler("/webjars/**")
                .addResourceLocations("classpath:/META-INF/resources/webjars/")
                .setCachePeriod(getSeconds(cachePeriod)).setCacheControl(cacheControl));
    }
    String staticPathPattern = this.mvcProperties.getStaticPathPattern();
    if (!registry.hasMappingForPattern(staticPathPattern)) {
        customizeResourceHandlerRegistration(registry.addResourceHandler(staticPathPattern)
                .addResourceLocations(getResourceLocations(this.resourceProperties.getStaticLocations()))
                .setCachePeriod(getSeconds(cachePeriod)).setCacheControl(cacheControl));
    }
}
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/**
 * Configuration equivalent to {@code @EnableWebMvc}.
 */
@Configuration(proxyBeanMethods = false)
public static class EnableWebMvcConfiguration extends DelegatingWebMvcConfiguration implements ResourceLoaderAware {

    private final ResourceProperties resourceProperties;

    private final WebMvcProperties mvcProperties;

从容器中获取所有的webmvcconfigurer,然后全部调用一遍 
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/*
 *
 * @author Rossen Stoyanchev
 * @since 3.1
 */
@Configuration(proxyBeanMethods = false)
public class DelegatingWebMvcConfiguration extends WebMvcConfigurationSupport {

    private final WebMvcConfigurerComposite configurers = new WebMvcConfigurerComposite();


    @Autowired(required = false)
    public void setConfigurers(List<WebMvcConfigurer> configurers) {
        if (!CollectionUtils.isEmpty(configurers)) {
            this.configurers.addWebMvcConfigurers(configurers);
        }
    }
springmvc的自动配置和我们的扩展配置都会起作用 ### 全面接管mvc 不要Springboot的mvc了，完全自己接管，使用@EnableWebMvc，那么web的自动配置全部失效，甚至静态资源都无法使用 ### 为什么enablewebmvc就全部失效呢 
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@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.TYPE)
@Documented
@Import(DelegatingWebMvcConfiguration.class)
public @interface EnableWebMvc {
}
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public class DelegatingWebMvcConfiguration extends WebMvcConfigurationSupport {
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@Configuration(proxyBeanMethods = false)
@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 {

当容器中没有WebMvcConfigurationSupport的时候，自动配置才开始生效，enablewebmvc帮我们导入了这个，所以失效了 ### 如何修改SpringBoot的默认配置 springboot先看容器中有没有用户自己配置的，如果有就用用户配置的，没有才自动配置

在springboot中有很多xxxConfiguier帮助我们扩展配置， ## 在骚一点 

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@Configuration
//@EnableWebMvc
public class MyMvcConfig extends WebMvcConfigurerAdapter {
    @Override
    public void addViewControllers(ViewControllerRegistry registry) {
        super.addViewControllers(registry);
        registry.addViewController("/wsx").setViewName("templates_hello");
    }

    @Bean
    public WebMvcConfigurerAdapter webMvcConfigurerAdapter(){
        return new WebMvcConfigurerAdapter() {
            @Override
            public void addViewControllers(ViewControllerRegistry registry) {
                registry.addViewController("/wsx2").setViewName("templates_hello");
                registry.addViewController("/wsx3").setViewName("templates_hello");
            }
        };
    }
}
### 引入bootstrap的webjars 官网 
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<!--        bootstrap-->
        <dependency>
            <groupId>org.webjars</groupId>
            <artifactId>bootstrap</artifactId>
            <version>4.0.0</version>
        </dependency>

### @/webjars/bootstrap/4.0.0/css/bootstrap.css 这个语法很好，因为当我们的项目名字变了的时候，不需要去修改所有的url， server.context-path=/crud