How to Serve Static Resources in Spring Boot: From Basic to Custom Configurations

1. The simplest (but inefficient) approach

We can create a controller that reads a file from the resources/html directory and writes its bytes to the response. The code below demonstrates this method, which works for text files but is not suitable for production.

@Controller
public class StaticResourceController {

    @RequestMapping("/static/**")
    public void getHtml(HttpServletRequest request, HttpServletResponse response) {
        String uri = request.getRequestURI();
        String[] arr = uri.split("static/");
        String resourceName = "index.html";
        if (arr.length > 1) {
            resourceName = arr[1];
        }
        String url = StaticResourceController.class.getResource("/").getPath() + "html/" + resourceName;
        try {
            FileReader reader = new FileReader(new File(url));
            BufferedReader br = new BufferedReader(reader);
            StringBuilder sb = new StringBuilder();
            String line = br.readLine();
            while (line != null) {
                sb.append(line);
                line = br.readLine();
            }
            response.getOutputStream().write(sb.toString().getBytes());
            response.flushBuffer();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

2. Spring Boot’s default static resource locations

Spring Boot automatically serves files placed under any of the following classpath directories:

classpath:/public/

classpath:/resources/

classpath:/static/

classpath:/META-INF/resources/

After creating these directories under src/main/resources, files such as 1.html – 4.html can be accessed via URLs like http://localhost:8080/1.html.

3. Custom static resource directory

To serve resources from a custom folder, define a configuration class that registers a resource handler:

@Configuration
public class ImageMvcConfig extends WebMvcConfigurerAdapter {
    @Override
    public void addResourceHandlers(ResourceHandlerRegistry registry) {
        registry.addResourceHandler("/image/**")
                .addResourceLocations("classpath:/images/");
    }
}

Alternatively, the same mapping can be declared in application.yml:

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

After placing an image (e.g., spring.jpg) in src/main/resources/images, it is reachable at http://localhost:8080/image/spring.jpg.

4. Summary

Spring Boot serves static resources from the four default locations listed above, with the lookup order giving priority to classpath:/META-INF/resources/. This order can be changed by redefining spring.resources.static-locations. Custom directories can be added either via a WebMvcConfigurer implementation or through application.yml.