SpringBoot的Web开发

一、创建Web项目

创建的时候勾选对应web选项即可，会自动引入相应的starter，pom如下：

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-web</artifactId>
</dependency>

里面的具体依赖不一一展开了。

二、SpringBoot的Web自动配置

经过前面的研究，知道主要是springboot为我们引入了org.springframework.boot.autoconfigure.web包的

1.自动配置类：xxxxAutoConfiguration帮我们给容器中自动配置组件；

2.配置文件封装类：xxxxProperties:配置类来封装配置文件的内容；

eg：DispatcherServletAutoConfiguration、WebMvcAutoConfiguration和WebMvcProperties、ResourceProperties

具体自动配置帮我们做了什么可以看xxxxAutoConfiguration，我们配置文件能配置什么属性可以看xxxxProperties。

三、springboot web的静态资源映射规则

1.ResourceProperties

@ConfigurationProperties(prefix = "spring.resources", ignoreUnknownFields = false)
public class ResourceProperties {

    private static final String[] CLASSPATH_RESOURCE_LOCATIONS = {
            "classpath:/META-INF/resources/", "classpath:/resources/",
            "classpath:/static/", "classpath:/public/" };

    /**
     * Locations of static resources. Defaults to classpath:[/META-INF/resources/,
     * /resources/, /static/, /public/].
     */
    private String[] staticLocations = CLASSPATH_RESOURCE_LOCATIONS;

    /**
     * Whether to enable default resource handling.
     */
    private boolean addMappings = true;

    private final Chain chain = new Chain();

    private final Cache cache = new Cache();

    public String[] getStaticLocations() {
        return this.staticLocations;
    }

    public void setStaticLocations(String[] staticLocations) {
        this.staticLocations = appendSlashIfNecessary(staticLocations);
    }

    private String[] appendSlashIfNecessary(String[] staticLocations) {
        String[] normalized = new String[staticLocations.length];
        for (int i = 0; i < staticLocations.length; i++) {
            String location = staticLocations[i];
            normalized[i] = location.endsWith("/") ? location : location + "/";
        }
        return normalized;
    }

可以看到springboot自动配置默认回到

"classpath:/META-INF/resources/",
"classpath:/resources/",
"classpath:/static/", 
"classpath:/public/"
目录下寻找静态资源。
2.WebMvcAuotConfiguration

@Override
        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));
            }
            String staticPathPattern = this.mvcProperties.getStaticPathPattern();
              //静态资源文件夹映射
            if (!registry.hasMappingForPattern(staticPathPattern)) {
                customizeResourceHandlerRegistration(
                        registry.addResourceHandler(staticPathPattern)
                                .addResourceLocations(
                                        this.resourceProperties.getStaticLocations())
                        .setCachePeriod(cachePeriod));
            }
        }

        //配置欢迎页映射
        @Bean
        public WelcomePageHandlerMapping welcomePageHandlerMapping(
                ResourceProperties resourceProperties) {
            return new WelcomePageHandlerMapping(resourceProperties.getWelcomePage(),
                    this.mvcProperties.getStaticPathPattern());
        }

　　　　　　private Optional<Resource> getWelcomePage() {
　　　　　　　　String[] locations = getResourceLocations(
　　　　　　　　this.resourceProperties.getStaticLocations());
　　　　　　　　return Arrays.stream(locations).map(this::getIndexHtml)
　　　　　　　　.filter(this::isReadable).findFirst();
　　　　　　}

　　　　　　private Resource getIndexHtml(String location) {
　　　　　　　　return this.resourceLoader.getResource(location + "index.html");
　　　　　　}

//配置喜欢的图标
        @Configuration
        @ConditionalOnProperty(value = "spring.mvc.favicon.enabled", matchIfMissing = true)
        public static class FaviconConfiguration {

            private final ResourceProperties resourceProperties;

            public FaviconConfiguration(ResourceProperties resourceProperties) {
                this.resourceProperties = resourceProperties;
            }

            @Bean
            public SimpleUrlHandlerMapping faviconHandlerMapping() {
                SimpleUrlHandlerMapping mapping = new SimpleUrlHandlerMapping();
                mapping.setOrder(Ordered.HIGHEST_PRECEDENCE + 1);
                  //所有  **/favicon.ico 
                mapping.setUrlMap(Collections.singletonMap("**/favicon.ico",
                        faviconRequestHandler()));
                return mapping;
            }

            @Bean
            public ResourceHttpRequestHandler faviconRequestHandler() {
                ResourceHttpRequestHandler requestHandler = new ResourceHttpRequestHandler();
                requestHandler
                        .setLocations(this.resourceProperties.getFaviconLocations());
                return requestHandler;
            }

        }

1.webjars：允许我们以jar的方式引入静态资源（http://www.webjars.org/），如jQuery

<!--引入jquery-webjar-->在访问的时候只需要写webjars下面资源的名称即可
        <dependency>
            <groupId>org.webjars</groupId>
            <artifactId>jquery</artifactId>
            <version>3.3.1</version>
        </dependency>

访问路径：localhost:8080/webjars/jquery/3.3.1/jquery.js

2.欢迎页，默认静态资源根目录/ndex.html

3.页面标签页图标，默认静态资源根目录/favicon.ico

四、Web自定义设置

以上这些都是了解到的默认配置，但有的时候不满足实际需求需要我们自定义配置，下节边自定义边研究原理。