Spring Boot Web 开发

1. 静态资源访问

1.1 静态资源目录

/static, /public, /resources, /META-INF/resources
默认映射路径是 /**（/** 默认是拦截所有请求）

classpath:/static
classpath:/public
classpath:/resources
classpath:/META-INF/resources

image.png

请求地址 http://localhost:8888/public.jpg

1.2 静态资源和动态资源地址一样

请求优先找 Controller 处理，若不能处理，再找静态资源处理器
可以指定拦截的前缀来访问静态资源

2. 配置静态资源地址

2.1 方式一：配置 application.yml

spring:
  mvc:
    static-path-pattern: /static/** # 指定访问路径前缀

请求地址 http://localhost:8888/static/public.jpg

指定静态资源目录

spring:
  mvc:
    static-path-pattern: /static/**
  web:
    resources:
      static-locations: classpath:/images,classpath:/static

请求地址 http://localhost:8888/static/demo.jpg

2.2 方式二：继承 WebMvcAutoConfiguration

• Deprecated as of 5.0 WebMvcConfigurer has default methods
• Spring Boot 2.0以后，该类被标记为@Deprecated（弃用）。官方推荐直接实现WebMvcConfigurer接口或者直接继承WebMvcConfigurationSupport类

@Configuration
public class WebConfig extends WebMvcConfigurerAdapter {
    @Override
    public void addResourceHandlers(ResourceHandlerRegistry registry) {
        // 将 /static/** 访问映射到/public/**
        registry.addResourceHandler("/static/**").addResourceLocations("classpath:/public/");
        // super.addResourceHandlers(registry);
    }
}

访问地址 http://localhost:8888/static/public.jpg

2.3 方式三：WebMvcConfigurer

@Configuration
public class WebConfig implements WebMvcConfigurer {
    @Override
    public void addResourceHandlers(ResourceHandlerRegistry registry) {
        registry.addResourceHandler("/img/**")
                .addResourceLocations("classpath:/static/")
                .addResourceLocations("classpath:/public/")
                .addResourceLocations("classpath:/resources/");
    }
}

访问地址 http://localhost:8888/img/public.jpg

3. 静态资源配置原理

Spring Boot启动默认加载 xxxAutoConfiguration 类

SpringMVC自动配置类org.springframework.boot.autoconfigure.web.servlet.WebMvcAutoConfiguration

@AutoConfiguration(after = { DispatcherServletAutoConfiguration.class, TaskExecutionAutoConfiguration.class,
        ValidationAutoConfiguration.class })
@ConditionalOnWebApplication(type = Type.SERVLET)
@ConditionalOnClass({ Servlet.class, DispatcherServlet.class, WebMvcConfigurer.class })
@ConditionalOnMissingBean(WebMvcConfigurationSupport.class)
@AutoConfigureOrder(Ordered.HIGHEST_PRECEDENCE + 10)
public class WebMvcAutoConfiguration {

  public static class WebMvcAutoConfigurationAdapter implements WebMvcConfigurer, ServletContextAware {
      public void addResourceHandlers(ResourceHandlerRegistry registry) {}
  }
}

配置类只有一个有参构造器，有参构造器所有参数的值都会从容器中确定

@EnableConfigurationProperties({ WebMvcProperties.class, WebProperties.class })
public static class WebMvcAutoConfigurationAdapter implements WebMvcConfigurer, ServletContextAware {
  public WebMvcAutoConfigurationAdapter(WebProperties webProperties, WebMvcProperties mvcProperties,
                                      ListableBeanFactory beanFactory, ObjectProvider<HttpMessageConverters> messageConvertersProvider,
                                      ObjectProvider<WebMvcAutoConfiguration.ResourceHandlerRegistrationCustomizer> resourceHandlerRegistrationCustomizerProvider,
                                      ObjectProvider<DispatcherServletPath> dispatcherServletPath,
                                      ObjectProvider<ServletRegistrationBean<?>> servletRegistrations) {
    this.resourceProperties = webProperties.getResources();
    this.mvcProperties = mvcProperties;
    this.beanFactory = beanFactory;
    this.messageConvertersProvider = messageConvertersProvider;
    this.resourceHandlerRegistrationCustomizer = resourceHandlerRegistrationCustomizerProvider.getIfAvailable();
    this.dispatcherServletPath = dispatcherServletPath;
    this.servletRegistrations = servletRegistrations;
    this.mvcProperties.checkConfiguration();
}
}

配置文件相关属性绑定

@ConfigurationProperties(prefix = "spring.mvc")
public class WebMvcProperties {
}
@ConfigurationProperties("spring.web")
public class WebProperties {
}