Resources

The Resource interface represents abstract resource. This allows you to process resources in the same way, whether the resource is specified by URL, file, byte array and etc.

The DispatcherServlet servlet provides default handling of resources. In most cases you need just save the resource file in appropriate folder like "resources/static" in your project.

resource paths

The default resource paths are defined in the ResourceProperties class.

You can register own resources path for uploading new resources or to save resources created by your application. This is very useful when application is executed as a jar file because default paths in this case are read-only.

If several paths have resources with the same file name, then the file will be taken from the first path in the registration order. Thus, you can dynamically replace a resource from a JAR file with a new resource without redeploying the application.

@Configuration
//@AutoConfigureAfter(DispatcherServletAutoConfiguration::class)
class AppConfig : WebMvcConfigurer {

override fun addResourceHandlers(registry: ResourceHandlerRegistry) {
  val locations = arrayOf(
    "file:./resources/", // our new folder
    "classpath:/META-INF/resources/",
    "classpath:/resources/",
    "classpath:/static/",
    "classpath:/public/")

  // create new resource folder and subfolder "files"
  File(File("."), "resources").apply {
      mkdirs()
      File(this, "files").mkdirs()
     }

  registry.addResourceHandler("/**") 
    .addResourceLocations(*locations)
    .setCacheControl(CacheControl.maxAge(30, TimeUnit.DAYS)
         .cachePublic())
  }
}

@Configuration
public class AppConfiJ implements WebMvcConfigurer {

    @Override
    public void addResourceHandlers(ResourceHandlerRegistry registry) {
        String[] locations = {
                "file:./resources/",
                "classpath:/META-INF/resources/",
                "classpath:/resources/",
                "classpath:/static/",
                "classpath:/public/"};

        File newResFolder = new File(new File("."), "resources");
        newResFolder.mkdirs();
        // additional subfolder
        new File(newResFolder, "files").mkdirs();

        registry.addResourceHandler("/**")
                .addResourceLocations(locations)
                .setCacheControl(CacheControl.maxAge(30, TimeUnit.DAYS)
                        .cachePublic());
    }
}

Also you can try set paths in the application.properties file.

spring.resources.static-location=file:./resources,classpath:static,...

loading resource

// create loader instance and load resource
val res : Resource = DefaultResourceLoader()
                        .getResource("classpath:myres.txt")

//---------------------------------
// in bean you can use injecting

@Autowired // inject loader
lateinit var resourceLoader : ResourceLoader;
...
val res : Resource = resourceLoader.getResource("classpath:myres.txt")

// inject resource directly
@Value("classpath:myres.txt")
lateinit var res : Resource;

// shorthand loading by resource class
val resArray = arrayOf(ClassPathResource(cpRes),
                       FileSystemResource(fileRes)) 

resource resolving

You can change the default resource resolver or create a chain of resolvers. PathResourceResolver must be last resolver in chain if it is used.

override fun  addResourceHandlers(registry: ResourceHandlerRegistry) {
    registry.addResourceHandler(resHandler)
      .addResourceLocations(resLocations)
      .resourceChain(true)
      .addResolver(new GzipResourceResolver())
      .addResolver(new PathResourceResolver())
}

@Override
public void addResourceHandlers(ResourceHandlerRegistry registry) {
    registry.addResourceHandler(resHandler)
      .addResourceLocations(resLocations)
      .resourceChain(true)
      .addResolver(new GzipResourceResolver())
      .addResolver(new PathResourceResolver());
}

built-in Resource implementations

built-in resource loaders

built-in resource resolvers